,,m9]als ,,9 ,,rock ,,sections ,,! ,,practical ,,me?ods ,,( ,,id5tify+ ,,m9]als ,,9 ,,rock ,,sections ,,) ,,! ,,microscope ,,especially ,,arrang$ ,,= ,,/ud5ts ,,9 ,,te*nical ,,& ,,sci5tific ,,s*ools ,,by ,,lea ,mc,i,l,v,a,i,n,e ,,luqu]1 ,c4,e41 ,,ph4,d4 ,late ,assi/ant ,pr(essor ( ,m9]alogy1 ,columbia ,univ]sity1 ,new ,york ,city ,,f\r? ,,revis$ ,,edition ,illu/ration3 ,logo ,,new ,,york ,d4 ,,van ,,no/r& ,,company1 ,,inc4 #bej ,,f\r? ,,av5ue ,copyright1 #aiac ,,by ,,lea ,,mcilva9e ,,luqu] ,,lanca/] ,,press1 ,,inc ,,lanca/]1 ,,pa4 ,,preface ,,to ,,f\r? ,,revis$ ,,edition1 #aiac4 ,?is edition is practically t ( #aijh1 ) necess>y m9or revisions & corrections1 especially ! data ref]r+ to indices ( refraction & /r5g? ( d\ble refraction4 ,! values ( ! refractive indices & are record$ z well z ! mean values4 ,ref]5ces are also giv5 to 8,! ,me?ods ( ,petrographic-,microscopic ,rese>*10 by ,f4 ,e4 ,wright1 #aiab1 = exact 7quantitative7 me?ods ( det]m9+ cry/al con/ants4 ,,lea ,,mci4 ,,luqu]4 ,,dep>tm5t ,,( ,,m9]alogy1 ,,columbia ,,univ]sity1 ,,new ,,york1 ,may1 #aiac4 ,,preface ,,to ,,?ird ,,revis$ ,,edition1 #aijh4 ,! #aijh edition is ess5tially ! same z t ( #aije2 ! only *anges be+ 9 ! nature ( corrections1 & ! addition ( a brief description ( ! ,s*rd] van d] ,kolk me?od ( det]m9+ refractive indices & also an abbreviat$ diagram = det]m9+ tricl9ic feldsp>s 9 sections %[+ bo? ,c>lsbad & ,albite tw9n+4 ,! ,naumann symbols = cry/al =ms h also be5 omitt$4 ,,lea ,,mci4 ,,luqu]4 ,,dep>tm5t ,,( ,,m9]alogy1 ,,columbia ,,univ]sity1 ,,new ,,york1 ,april1 #aijh4 ,,preface ,,to ,,revis$ ,,edition1 #aije4 ,9 prep>+ ! revis$ edition1 ,*apt]s ,i4 & ,,iv4 h be5 rewritt5 & enl>g$ & ! "p relat+ to ! det]m9ation ( ! plagioclases has be5 greatly amplifi$4 ,_m additions h also be5 made to ,*apt] ,,iii4 & ! ,becke me?od1 = ! det]m9ation ( ! relative indices ( refraction ( m9]als1 has be5 giv5 9 detail4 ,"s new & useful tables h be5 introduc$2 z tables ( refractive indices 7mean7 & d\ble refraction 7maximum74 ,a diagram has also be5 add$1 %[+ ! relation exi/+ betwe5 /r5g? ( d\ble refraction1 int]f]5ce colors & ?ickness ( section4 ,pr(essor ,e4 ,we9s*5k's admirable text-book1 8,die ,ge/e9sbild5d5 ,m9]ali501 ,freiburg1 #aija1 has be5 specially ref]r$ to1 & ! tables ( refractive indices & d\ble refraction h be5 compil$ f ,we9s*5k's new ,tables4 ,_m new cuts h be5 add$1 among !m be+ semi-ideal draw+s1 %[+ typical outl9es ( cry/al sections1 cleavage1 optical ori5tation1 etc4 ,9 describ+ ! 8,usual ,appe>ance 9 ,sections0 ( a m9]al1 x is ( c\rse only possible to m5tion ! usual cry/al =m 9 :i* ! m9]al occurs 9 a rock4 ,! cry/al may be cut 9 any way by ! plane ( ! section2 b a g5]al k ( ! cry/al =ms w furni% an idea z to ! outl9e1 etc41 t ! m9]al may %[ 9 ! section4 ,,lea ,,mci4 ,,luqu]4 ,,dep>tm5t ,,( ,,m9]alogy1 ,,columbia ,,univ]sity1 ,,new ,,york1 ,july1 #aije4 ,,preface ,,to ,,fir/ ,,edition1 #ahih4 ,! id5tification ( m9]als 9 rock sections ) ! microscope1 includ+ z x does a k ( optical m9]alogy1 is (t5 difficult = beg9n]s4 ,?is may be due to ! fact t mo/ ( ! publications on ?is subject are q elaborate 9 _! nature & 9 ei!r ,fr5* or ,g]man4 ,:ile detail$ descriptions are v necess>y1 &1 9 fact1 indisp5sable = advanc$ inve/igation1 !y are apt to prove cumb]some & confus+ at fir/4 ,= ^! reasons ?is text-book has be5 prep>$ by ! writ]1 ) a view ( putt+ be=e ! /ud5t only ^? facts :i* are absolutely necess>y = ! prop] recognition & id5tification ( ! common m9]als 9 rock sections4 ,! footnotes ref] ! /ud5t to /&>d publications1 9 :i* are giv5 details ( ! me?ods & inve/igations outl9$ 9 ! text4 ,an elem5t>y k ( cry/allography & m9]alogy is almo/ indisp5sable & is "h assum$4 ,! microscopic & optical *>act]s ( ! m9]als are record$ 9 ! usual ord] 9 :i* !y w\ld be obs]v$ ) a petrographical microscope4 ,ne>ly all ! rock-=m+ m9]als become transp>5t 9 ?9 sections2 b :5 opaque1 att5tion is call$ to ! fact & ! *>act]s are record$ z se5 ) incid5t light4 ,:ite light is assum$ to be us$1 unless o!rwise /at$4 ,! int]f]5ce colors record$ 9 all cases are ^? giv5 by v ?9 sections ( #j4jc mm4 9 ?ickness4 ,! ord] foll[$ = ! m9]als is ess5tially t ( ,ros5bus* 7bas$ on ! symmetry ( ! cry/all9e =m71 ) a few exceptions made = conv5i5ce1 su* z plac+ pyrrhotite aft] pyrite & zoisite aft] epidote4 ,! /atem5ts reg>d+ ! occurr5ces ( m9]als 9 ! common rock-types h be5 tak5 ma9ly f ,les ,m9raux des ,ro*es1 by ,lvy & ,lacroix4 ,! t]ms axes & directions ( ela/icity1 us$ ?r\gh\t ?is book1 are v commonly employ$ 9 petrographical lit]ature ( ! pres5t "t4 ,^! axes & directions %\ld probably m correctly be call$ axes & directions ( vibration or ext9ction4 ,! reasons = or aga9/ ! ela/ic condition ( ! 8e!r0 are ( m int]e/1 h[ev]1 to ! physici/ ?an to ! petrograph]4 ,an optical s*eme is app5d$1 ) ! m9]als gr\p$ accord+ to _! common optical *>act]s4 ,! writ]'s ?anks are due to ,dr4 ,a4 ,j4 ,moses1 ,pr(essor ( ,m9]alogy1 & to ,mr4 ,j4 ,f4 ,kemp1 ,pr(essor ( ,geology1 = k9d sugge/ions (f]$ dur+ ! prep>ation ( ?is book4 ,,lea ,,mci4 ,,luqu]4 ,,dep>tm5t ,,( ,,m9]alogy1 ,,columbia ,,univ]sity1 ,n4 ,y4 ,,city1 ,octob]1 #ahih4 ,,table ,,( ,,cont5ts ,,page4 ,,conv5tions ,,& ,,abbreviations ix ,,*apt] ,i4 ,,introductory ,,optics ,,= ,,optical ,,m9]alogy4 ,ord9>y ,light4--,plane ,pol>iz$ ,light4--,effects ,produc$ by ,cry/al ,sections on ,transmitt$ ,light4--,amorph\s ,bodies4--,isotropic ,cry/als4--,anisotropic ,cry/als4--,d\ble ,refraction4--,uniaxial ,cry/als4--,biaxial ,cry/als4--,pr9cipal ,vibration ,directions4--,axial ,angle4--,disp]sion4 #a ,,*apt] ,,ii4 ,,petrographical ,,microscope4 ,reflector4--,pol>iz]4--,nicol ,prism4--,cond5s+ ,l5s4--,rotat+ ,/age4--,objectives4--,analyz]4--,eye-pi eces4 #g ,,*apt] ,,iii4 ,,inve/igation ,,( ,,microscopic ,,& ,,optical ,,*>act]s ,,( ,,m9]als4 ,opaque ,m9]als4 ,transp>5t ,m9]als3 ,) transmitt$ light3 ,=m1 ,color1 ,index ( ,refraction & ,relief1 ,becke ,me?od1 van d] ,kolk ,me?od1 ,cleavage1 ,fracture1 ,inclusions4 ,) pol>iz$ transmitt$ light3 ,pleo*roism4 ,) cross$ nicols3 ,isotropic ,"*1 ,anisotropic ,"*1 ,int]f]5ce ,colors1 ,ext9ction & ,ext9ction ,angles1 ,vibration ,directions ( ,fa/] & ,sl[] ,rays1 ,ord] ( ,int]f]5ce ,color1 ,/r5g? ( ,d\ble ,refraction1 ,det]m9ation ( ,m9]als & ,?ickness ( ,section1 ,/ructure4 ,) conv]g5t light3 ,uniaxial ,int]f]5ce ,figures & ,optical ,"*1 ,biaxial ,int]f]5ce ,figures & ,optical ,"*1 ,det]m9ation ( ,axial ,angle1 ,di/9ctions betwe5 ,or?orhombic1 ,monocl9ic & ,tricl9ic ,sections4 ,resum ( ,uses ( ,p>allel & ,conv]g5t ,pol>iz$ ,light4 #ac ,,*apt] ,,iv4 ,,microscopic ,,& ,,optical ,,*>act]s ,,( ,,m9]als4 ,amorph\s ,m9]als4--,isometric ,m9]als4--,tetragonal ,m9]als4--,hexagonal ,m9]als4--,or?orhombic ,m9]als4--,monocl9ic ,m9]als4--,tricl9ic ,m9]als4--,m9]al ,aggregates4 #ea ,,*apt] ,v4 ,,me?ods ,,( ,,prep>+ ,,sections4 ,cutt+ & ,gr9d+ ,ma*9es4--,saws4--,cutt+4--,gr9d+4 ,plates or ,laps4--,cem5t+4--,gr9d+4--,m\nt+4--,cle an+ & ,f9i%+4--,conv5i5t ,app>atus = "w4 #aag ,,*apt] ,,vi4 ,,*emical ,,& ,,me*anical ,,te/s4 ,*emical ,te/s on ,cry/al 9 ,section3 ,c>bonates1 ,gelat9iz+ ,silica4--,et*$ ,figures4--,heat+ ,section to ,r$ness4--,me?ods ( ,isolat+ ,cry/als or ,fragm5ts = ,te/+3 ,specific ,gravity ,sep>ation1 ,electro-magnetic ,sep>ation1 ,*emical ,sep>ation4--,micro-,*emical ,reactions3 ,bori*y's ,me?od1 ,behr5's ,me?od1 ,special ,te/s4 #abi ,,app5dix4 ,brief ,s*eme ( ,classification into ,sy/ems by ,optical ,det]m9ations4--,tables ( ,d\ble ,refraction 7maximum7 & ,indices ( ,refraction 7mean74--,diagram1 %[+ relation betwe5 /r5g? ( d\ble refraction1 int]f]5ce colors & ?ickness ( section4--,ord] ( ,consolidation ( ! ,con/itu5t ,m9]als 9 ,plutonic ,rocks4--,optical ,s*eme ) ,special ,introduction4 #ada ,,index4 #adi ,,conv5tions ,,& ,,abbreviations4 a ,! assum$ direction ( ! e!r vibrations ( ! fa/e/ ray4 b ,! assum$ direction ( ! e!r vibrations ( ! ray ) int]m$iate velocity4 c ,! assum$ direction ( ! e!r vibrations ( ! sl[e/ ray4 ,9 "s ,am]ican ,text-,books 7by ,idd+s1 ,w9*ell ,phillips7 a ,x1 b ,y & c ,z4 a ,! assum$ direction ( ! e!r vibrations ( ! fa/] ray 9 ! giv5 section4#a c ,! assum$ direction ( ! e!r vibrations ( ! sl[] ray 9 ! giv5 section4 77 ,optical "* positive4 77 ,optical "* negative4 ,p>allel to4 7 7 ,! diff]5ce betwe5 ! indices ( refraction ( ! sl[e/ & fa/e/ rays1 respectively1 transmitt$ by ! cry/al1 & indicates 9 decimals ! relative /r5g? ( ! d\ble refraction4 n ,! mean index ( refraction2#b h5ce 7 7_/#c or 7 #b7_/c4 ,index ( refraction ( ! fa/e/ ray4 ,index ( refraction ( ! sl[e/ ray4 a1 b & relate to ! cry/allographic axes commonly repres5t$ by ^! lett]s4 #b;,e ! app>5t axial angle measur$ 9 air1 #b,v be+ ! true angle4 ,bxa ,! acute bisectrix4 ,bxc ,! obtuse bisectrix4 ,ax4 pl4 ,! axial plane1 i4 e41 ! plane conta9+ ! two 8optic axes40 ,,elongation relates to ! appreciable ext5sion (t5 %[n by ! cry/al section4 ,a cry/al ( long prismatic habit1 cut ab\t p>allel to ! axis1 w\ld %[ m>k$ elongation2 :ile a tabul> cry/al 7l mica7 w\ld %[ elongation if cut at "r angles to ! tabul> faces4 ,at times1 ( c\rse1 no elongation is appreciable1 z 9 ! case ( granul> or brok5 cry/als or :]e ! cross-section is ess5tially squ>e or octagonal4 ,v (t5 ! relation ( ! cleavage is giv5 to ! elongation & also to ! directions a & c1 :i* makes x possible to te/ = a & c ev5 :5 no m>k$ elongation c be obs]v$4 ,,m9]als ,,9 ,,rock ,,sections4 ,,*apt] ,i4 ,,introductory ,,optics ,,= ,,optical ,,m9]alogy4 ,! object ( ?is introduction is m]ely to give a practical discussion ( elem5t>y optics1 z appli$ to optical m9]alogy1#c & no elaborate discussion ( ?is important subject w be attempt$4 ,! explanations w be made z simple z possible1 &1 9 mo/ cases1 only ! optical ph5om5a w be describ$ )\t ent]+ into a !oretical discussion z to ! cause ( ^! ph5om5a4 ,light#d may be reg>d$ z transmitt$ 9 /raight l9es by vibrations ( ! 8e!r10 tak+ place at "r angles to ! direction ( transmission4 ,ord9>y light is light ) ! e!r vibrations 9 all possible directions1 ! pa? describ$ by any p>ticle ( e!r con/antly *ang+4 ,plane pol>iz$ light is simply light ) ! e!r vibrations all p>allel to "o plane pass+ ?r\gh ! direction ( transmission4 ,by exp]im5t x has be5 prov$ t !re exi/s a v close relation betwe5 ! optical prop]ties ( cry/als & _! o!r physical prop]ties1 su* z =m1 color1 transmission ( heat1 etc4 ,!re=e x is (t5 possible1 by a c>eful optical inve/igation ( a cry/al section1 to det]m9e important cry/allographic facts1 ev5 9 ! abs5ce ( any di/9ct outl9e4 ,! ,effects ,produc$ by ,cry/als on ,transmitt$ ,light4 ,consid] t a s]ies ( optical te/s are made on all possible sections#e ( cry/als 9 ! six sy/ems1 & ! mann] 9 :i* ^! cry/als affect transmitt$ light asc]ta9$4 ,isotropic ,cry/als3 ,x w be f\nd t all sections ( ,isometric cry/als transmit light ) equal velocity 9 all directions2 t is1 ! cry/als are optically equival5t 9 all directions &1 h5ce1 c produce no d\ble refraction4#f ,9 ^! cry/als any section1 h[ev] cut1 w transmit all ! rays ( light1 incid5t to ! surface at "r angles1 ) no *ange4#g ,! same is true ( ,amorph\s bodies1 glass1 etc41 unless !y h be5 subject$ to /ra9s or peculi> conditions dur+ cool+4 ,a s+le image is se5 ?r\gh ^! isotropic sections4 ,illu/ration3 ,,fig4 #a4 ,anisotropic ,cry/als3 ,x w also be f\nd t ne>ly all sections 7! exceptions be+ giv5 lat]7 ( cry/als 9 ! rema9+ five sy/ems1 produce q a diff]5t effect on transmitt$ light4 ,9 ^! cry/als ! velocity ( transmission ( light v>ies ) ! vibration direction ( ! light rays4 ,?is prop]ty1 call$ d\ble refraction1#h seems to result f ! p[] ( resolv+ a ray ( ord9>y light1 ) e!r vibrations 9 all directions1 into two rays ) e!r vibrations 9 planes at "r angles to ea* o!r2 ! two result+ rays trav]s+1 usually1 div]g5t pa?s 9 pass+ ?r\gh ! section4 ,! m9]al calcite 7,icel& sp>7 exhibits ?is prop]ty to a m>k$ degree1 & 9 c]ta9 sections w %[ a d\ble image1 ,fig4 #a4 ,t ! vibration directions ( ! two d\bly refract$ rays are 9 planes at "r angles to ea* o!r1 c be easily prov$ by us+ a nicol prism4#i ,9 mo/ cases ! sep>ation ( ! two images is s slight z n to be p]ceiv$ by ! eye1 & ! practical me?od ( te/+ a cry/al section = d\ble refraction w be giv5 lat]1 p4 #bg4 ,! cry/als t %[ d\ble refraction are fur!r divid$ into two gr\ps1 uniaxial & biaxial3 7#a7 ,uniaxial1 or ^? 9 :i* ! optical *>act]s are symmetrical to "o direction1 call$ an optic axis4 ,?is optic axis is ! cry/allographic v]tical axis1 2 & p>allel to ?is direction !re is a s+le value only = ! light velocity & no d\ble refraction takes place4#aj ,h5ce any section p>allel to ! base 7#jja7 be+ at "r angles to ! optic axis1 acts l a section ( an isotropic cry/al & transmits all ! p]p5dicul>ly incid5t rays ( light ) no *ange4 ,9 any o!r section d\ble refraction takes place & x c be prov$ by us+ a nicol prism t ! two rays h e!r vibrations1 "o 9 ! plane pass+ ?r\gh ! incid5t ray & ! axis ( ! cry/al1 & ! o!r 9 a plane at "r angles !reto1 h5ce 9 ! basal plane4 ,?is latt] ray1 :i* has a con/ant velocity1 is call$ ! ord9>y ray ,o2 & ! o!r ray1 ) velocity v>y+ ) ! incl9ation ( ! section to 1 is call$ ! extraord9>y ray ,e4#aa ,! vibration directions are ei!r p>allel or symmetrical to cleavage cracks & cry/al outl9es4 ,9 sections p>allel to ! optic axis1 ! two d\bly refract$ rays h ! maximum diff]5ce 9 velocity ( transmission1 & h5ce _! vibration directions are call$ pr9cipal vibration directions#ab & ! plane conta9+ !m an optical pr9cipal section4 ,9 ^! sections ! refractive index ( ! ray vibrat+ p>allel to 7extraord9>y ray7 is d5ot$ by 1 & t ( ! ray vibrat+ p>allel to ! basal plane 7ord9>y ray7 by 4#ac ,to ?is gr\p belong all ,tetragonal & ,hexagonal cry/als4 7#b7 ,biaxial1 or ^? 9 :i* ! optical *>act]s are no long] symmetrical to an optic axis b to ?ree planes at "r angles to ea* o!r 7= mono*romatic light74 ,^! cry/als h1 h[ev] 7= light ( ea* wave-l5g? & = ea* temp]ature71 two directions p>allel to :i* !re is a s+le value only = ! light velocity & h5ce no d\ble refraction4 ,^! directions are call$ 8optic axes40#ad ,an inve/igation ( ^! biaxial cry/als %[s t ( all ! rays trav]s+ ^! cry/als !re are ?ree rays :i* advance ) maximum1 m9imum & "s int]m$iate velocity4 ,! vibration directions ( ^! ?ree rays are call$ ! pr9cipal vibration directions & are at "r angles to ea* o!r 7be+ ! int]sections ( ! ?ree planes above ref]r$ to74 ,! direction ( e!r vibration ( ! fa/e/ ray is d5ot$ by a1 ( ! sl[e/ ray by c1 & ( ! ray advanc+ ) int]m$iate velocity by b4#ae ,ea* ( ! ?ree planes1 conta9+ two pr9cipal vibration directions1 is call$ an optical pr9cipal section4 ,! index ( refraction ( ! a ray is d5ot$ by 1 ( ! b ray by 1 & ( ! c ray by 4 ,to ?is gr\p belong all cry/als 9 ! ,or?orhombic1 ,monocl9ic & ,tricl9ic sy/ems4 ,9 ! ,or?orhombic sy/em1 ! pr9cipal vibration directions are p>allel to ! cry/allographic axes2 h5ce all p9acoidal sections conta9 two ( ^! pr9cipal vibration directions4 ,9 all sections p>allel to ! ?ree cry/allographic axes 1 & 1 ! vibration directions are p>allel or symmetrical to cleavage cracks1 cry/al edges1 etc4 ,9 ! ,monocl9ic sy/em1 "o pr9cipal vibration direction is p>allel to ! or?o axis 1 ! o!r pr9cipal vibration directions are 9 ! plane ( symmetry1 at "r angles to 1 b are n p>allel ) ei!r ! v]tical axis or ! cl9o axis 4 ,9 cl9o p9acoid 7#jaj7 sections ! pr9cipal vibration directions w make def9ite angles ) cry/allographic l9es1 su* z cleavages or cry/al outl9es4 ,^! angles are call$ ext9ction angles4 ,!y w v>y1 9 ?is sy/em1 ) ref]5ce to ! direction ( ! axis f a maximum on ! cl9o p9acoid 7#jaj7 to #j on ! or?o p9acoid 7#ajj71 :5 ! vibration directions ( ! two d\bly refract$ rays w be p>allel & at "r angles to ! plane ( symmetry4 ,h5ce ! vibration directions are p>allel or symmetrical to cleavages1 edges1 etc41 only 9 sections p>allel to ! or?o axis 2 b 9 all o!r sections are unsymmetrical4 ,9 ! ,tricl9ic sy/em1 ! pr9cipal vibration directions are n p>allel to ! cry/allographic axes1 & !re is no def9ite relation betwe5 ^! directions & ! cry/allographic axes2 h5ce 9 all possible sections !re w be ext9ction angles4 ,9 all biaxial cry/als ! two optic axes are incl9$ to ea* o!r1 mak+ :at is call$ ! axial angle1 #b,v1 ! app>5t angle measur$ 9 air be+ #b;,e4 ,! optic axes lie 9 ! plane1 call$ ! axial plane1 :i* conta9s ! pr9cipal vibration directions a & c4 ,! axial angles are bisect$ by ^! pr9cipal vibration directions1 ! direction bisect+ ! acute angle be+ call$ ! acute bisectrix1 ,bxa1 & t bisect+ ! obtuse angle ! obtuse bisectrix1 ,bxo4 ,an approximate idea ( ! value ( ! axial angle c be obta9$ by ! use ( ! petrographical microscope1 z describ$ lat]1 p4 #dg4 ,! axial angle is (t5 a conv5i5t di/9ction betwe5 su* m9]als z muscovite & biotite4 ,! axial angle w v>y ) ! temp]ature & ) light ( diff]5t wave-l5g? or color1 & ?is v>iation is call$ disp]sion ( ! optic axes4 ,disp]sion ( ! pr9cipal vibration directions also takes place 9 monocl9ic & tricl9ic cry/als1 b c be usually disreg>d$4 ,9 clos+ x is v important to rememb] t any section ( an anisotropic cry/al 7n at "r angles to an optic axis7 w always transmit two rays ( light ) diff]5t velocities & ) vibration directions 9 planes at "r angles to ea* o!r4 ,isometric cry/als1 ( c\rse1 produce no d\ble refraction ( light4 ,,*apt] ,,ii4 ,,! ,,petrographical ,,microscope4#af ,! petrographical microscope is ess5tially an ord9>y microscope#ag ) ! foll[+ important additional equipm5t4 ,x mu/ be provid$ )3 #a a pol>iz] 7a piece ( app>atus = giv+ pol>iz$ light7 plac$ bel[ ! /age2 #b an analyz] 7a piece ( app>atus = analyz+ ! rays ( light aft] !y h pass$ ?r\gh ! pol>iz] & transp>5t section7 plac$ betwe5 ! objective & ! eye2 #c a /age rotat+ ab\t an axis :i* is ! l9e ( sight ( ! microscope4 ,a conv5i5t type ( microscope is t made by ,seib]t ( ,wetzl> 7,no4 #aa a71 ,fig4 #b4 ,! reflector a is usually fitt$ ) a plane mirror on "o side1 & a p>abolic mirror on ! o!r4 ,! plane mirror %\ld be us$ ) sunlight1 & ! p>abolic mirror ) artificial light1 9 ord] to make ! rays ( light z ne>ly p>allel z possible4 ,! pol>iz] is 9 mo/ cases a nicol prism1 set 9 a suitable frame b1 & made z foll[s3 ,= ! nicol prism 8a cleavage rhomboh$ron ( calcite 7! v>iety ,icel& sp> is univ]sally us$ 9 consequ5ce ( its transp>5cy7 is obta9$1 hav+ f\r l>ge & two small rhomboh$ral faces opposite ea* o!r4 ,9 place ( ! latt] planes1 two new surfaces are cut1 mak+ angles ( #fh 7in/ead ( #ga7 ) ! obtuse v]tical edges2 ^! !n =m ! t]m9al faces ( ! prism4 ,9 addition to ?is1 ! prism is cut ?r\gh 9 ! direction ,,hh1 ,fig4 #c1 ! p>ts !n poli%$ & cem5t$ toge!r aga9 ) ,canada balsam4 ,a ray ( light1 ab1 ent]+ ! prism1 is divid$ into two rays pol>iz$ at "r angles to ea* o!r4 ,"o ( ^!1 bc1 on meet+ ! lay] ( balsam 7^: refractive index is less ?an t ( ! ray bc71 suff]s total reflection1 & is deflect$ aga9/ ! black5$ sides ( ! prism & ext+ui%$4 ,! o!r1 bd1 passes ?r\gh & em]ges at e1 a completely pol>iz$ ray ( light1 t is1 a ray ) vibrations 9 "o direction only1 & t ! direction ( ! %ort] diagonal ( ! prism40#ah ,! v]tical plane ?r\gh ! %ort] diagonal may be call$ ! plane ( vibration#ai ( ! nicol4 ,illu/ration3 ,,fig4 #b4 ,illu/ration3 ,,fig4 #c4 ,! pol>iz] mu/ be bel[ ! /age c1 & is g5]ally adju/$ s z to h its plane ( vibration p>allel to ! ,n4 & ,s4 cross-wire 9 ! eye-piece o4 ,x is important to "k ! direction ( ! plane ( vibration ( ! pol>iz] or l[] nicol1 z we c !n det]m9e1 :5 absorption ( light occurs 9 a m9]al1 ! direction 9 ?is m9]al p>allel to :i* ! absorb$ rays are vibrat+4 ,! pol>iz] slides 9 an out] %ell or frame1 &1 by means ( a lev] d1 c easily be rais$ or l[]$4 ,a conv5i5t te/ = ! location ( ?is plane ( vibration ( ! pol>iz] is z foll[s3 ,make use ( a section ( biotite1 cut at "r angles to ! basal plane1 h5ce %[+ ! basal cleavage cracks4 ,biotite has ! prop]ty ( absorb+ to a m>k$ ext5t ! light vibrat+ p>allel to ^! cleavage cracks4 ,rotate su* a section on ! /age ( ! microscope until ! position ( maximum d>kness is rea*$ & :5 su* is ! case ! plane ( vibration ( ! pol>iz] mu/ be p>allel to ^! cleavage cracks4 ,on ! top ( ! nicol is plac$ ! cond5s+ l5s = gett+ conv]g5t light1 & ! adju/m5ts are s arrang$ t :5 ! nicol is up z f> z x w g1 ! cond5s+ l5s#bj is br\ght almo/ 9 contact ) ! l[] surface ( ! transp>5t section re/+ on ! /age4 ,! rotat+ circul> /age e is support$ on a suitable frame c1 & arrang$ s t its axis ( rotation co9cides ) ! l9e ( sight ( ! microscope4 ,! /age is graduat$1 &1 by means ( an index fix$ to ! frame1 ! angul> rotation c always be obta9$4 ,x is also provid$ ) two adju/+ screws#ba f1 by means ( :i* ! axis ( rotation c be accurately c5t]$4 ,! me?od ( c5t]+ is z foll[s3 ,br+ "s prom95t m>k 9 ! section exactly 9 co9cid5ce ) ! int]section ( ! cross-wires 9 ! eye-piece4 ,rotate ! /age #ahj1 & correct "o half ! error by means ( ! c5t]+ screws1 & ! o!r half by mov+ ! section on ! /age4 ,*eck ! result by rotat+ ! /age #ahj aga91 & if necess>y repeat ! corrections 9 ! same way until ! adju/m5t is satisfactory4 ,! objective#bb g screws into ! coll> h1 :i* has a slot k1 9 ! upp] portion1 = ! introduction ( a s5sitive color plate1 a "o qu>t] undulation mica plate or a qu>tz w$ge4#bc ,! slot k is s arrang$ t1 :5 ! s5sitive color plates are introduc$1 ! vibration directions ( ^! plates w make an angle ( #de ) ! planes ( vibration ( ! cross$ nicols1 & ! int]f]5ce color w ?us be at its maximum int5sity4 ,a revolv+ nose-piece is sometimes us$ :i* c be atta*$ to ! coll> h & arrang$ to c>ry two or ?ree objectives1 :i* c ?us be v quickly br\ght into position = use4 ,?is is conv5i5t 9 pass+ rapidly f obs]vations ) p>allel light to obs]vations ) conv]g5t light1 :i* mu/ be made ) a high p[] objective4 ,! difficulty is t rec5t]+ is g5]ally requir$4 ,! mod]n microscopes are provid$ ) a clip = hold+ ! objectives1 in/ead ( ! screw-?read coll> h4 ,! analyz]#bd or upp] nicol is conta9$ 9 ! frame l1 :i* is arrang$ s z to slide 9 & out ( ! tube ( ! microscope4 ,! plane ( vibration ( ! analyz] is fix$ by ! in/rum5t mak] s z to be at "r angles to ! plane ( vibration ( ! pol>iz]1 h5ce 9 ! ,seib]t microscope p>allel to ! ,e4 & ,w4 cross-wire 9 ! eye-piece4 ,consequ5tly :5 ! frame l is pu%$ into ! tube1 ! analyz] is introduc$ 9 ! l9e ( sight betwe5 ! objective & ! obs]v]'s eye1 ) its plane ( vibration at "r angles to ! plane ( vibration ( ! pol>iz]2 t is ! nicols are cross$4 ,:5 ! nicols are cross$1 if !y are prop]ly adju/$1 no light c pass ?r\gh to ! eye & ! field ( view %\ld be d>k4#be ,! eye-piece#bf o fits into ! top ( ! tube1 &1 by means ( a little project+ piece fitt+ into a slot 9 ! frame1 c always be adju/$ s z to h its cross-wires p>allel to ! planes ( vibration ( ! two nicols4#be ,"s in/rum5ts are provid$ ) an additional slot 9 ! tube betwe5 ! analyz] & ! eye-piece = ! introduction ( a ,b]tr& l5s1 :i* is us$ to magnify ! int]f]5ce figures produc$ by conv]g5t light4 ,! fir/ approximate focus+ is made by ! screw m1 & ! f9e adju/m5t by ! screw n4 ,9 focus+ always />t ) ! objective v ne> ! section1 & move x away until ! "r focus is obta9$4 ,nev] move d[n t[>ds ! section 9 obta9+ ! focus1 z !re is dang] !n ( /rik+ ! objective aga9/ ! section4 ,= clean+ ! microscope xylol c be us$1 z x w n injure ! lacqu]4 ,to lubricate any ( ! p>ts use a small quantity ( s(t tall[1 good clock oil or p>aff9 oil4 ,,*apt] ,,iii4 ,,inve/igation ,,( ,,microscopic ,,& ,,optical ,,*>act]s ,,( ,,m9]als4 ,*>act]s ( ,opaque ,m9]als1 obs]v$ by reflect$ light4 ,! m9]als :i* rema9 p]fectly opaque 9 ?9 rock sections h usually metallic lu/re & are v m9ute 9 size1 z is ! case ) ! iron ores4 ,:5 ! metallic m9]als ( a rock specim5 are di/9ctly se5 ) ! unaid$ eye1 x is r>ely necess>y to make a section = _! det]m9ation1 z ?is c m easily be done by any ( ! well kn[n bl[pipe me?ods4 ,=m1 ,lu/re1 ,color1 ,cleavage1 etc41 are recogniz$ 9 ! same way z 9 ! case ( macroscopic specim5s4 ,9 ord] to make ! obs]vations by reflect$ light alone1 ! beam ( light f ! reflector-mirror mu/ be cut (f by hold+ ! h& ov] ! mirror or by mov+ ! mirror4 ,*>act]s ( ,transp>5t ,m9]als1 obs]v$ by transmitt$ light4 ,! petrographical microscope = ^! obs]vations is suppos$ to be 9 ! condition ( an ord9>y microscope1 bo? nicols be+ out ( ! field & a /rong beam ( light com+ up ?r\gh ! transp>5t section f ! reflector bel[4 ,! *>act]s are consid]$ 9 ! ord] 9 :i* !y w\ld mo/ naturally appe> to ! obs]v] dur+ a complete inve/igation ) ! microscope4#bg ,illu/ration3 ,,fig4 #d4--;,idiomorphic augite cry/als 9 camptonite4 ,! section is ab\t at "r angles to ! v]tical axis 1 & %[s ! int]sect+ cleavages p>allel to ! prism ( #hg #jf4 ,ke5e ,valley1 ,n4 ,y4 ,illu/ration3 ,,fig4 #e4--;,allotriomorphic qu>tz q1 %[+ no 8relief10 plagioclase p & decompos$ feldsp> o 9 granite4 ,z se5 ) cross$ nicols4 7a7 ,=m4#bh ,cry/als b\nd$ by planes1 i4 e41 cry/als t h =m$ :5 conditions 7 favorable = complete developm5t4 ,su* cry/als are (t5 call$ idiomorphic or automorphic1 see ,fig4 #d4 ,cry/als t are l>ge 9 comp>ison ) o!r accompany+ cry/als may be call$ ,ph5ocry/s4 ,( c\rse cry/als1 :i* are n :olly conta9$ )9 ! rock section1 w only %[ ! outl9e ( ! b\nd+ planes cut by ?is p>ticul> section4 ,9 "s cases1 by a c>eful /udy ( ! outl9e ( sev]al sections ( ! same m9]al & by a measurem5t ( ! angles1 x is possible to det]m9e ! common 8cry/allographic =ms0 ( ! m9]al4 ,v mislead+ outl9es may1 h[ev]1 be obs]v$2 z = example ! triangul> outl9e ( a section ( a cube1 ) ! corn] truncat$4 ,= measur+ ! angles h ! /age accurately c5t]$1 !n br+ ! v]tex ( ! angle to be measur$ to ! int]section ( ! cross-wires 9 ! eye-piece4 ,br+ "o ( ! sides 9 co9cid5ce ) "o ( ! cross-wires4 ,note ! read+ ( ! graduat$ circle & rotate ! section until ! o!r side is 9 co9cid5ce ) ! same wire4 ,take ! read+ aga9 & ! diff]5ce w be ! angle requir$4 ,cry/als )\t b\nd+ planes1 ^: surfaces are m or less det]m9$ by ^? ( adjac5t cry/als4 ,su* cry/als are frequ5tly call$ allotriomorphic or x5omorphic1#bi see ,fig4 #e4 ,?is allotriomorphic =m mu/ n be conf\nd$ ) ! worn or r\nd$ b\nd>ies ( ! compon5t gra9s 9 cla/ic rocks4 ,illu/ration3 ,,fig4 #f4--;,corrod$ sanid9e cry/al 9 p]lite4 ,corrod$ ,cry/als1#cj ^: frett$ outl9e is und\bt$ly due to corrosive action ( ! magma1 see ,fig4 #f4 ,brok5 or ,/ra9$ ,cry/als4 ,9 "s cases :at 7 =m]ly l>g] individuals h be5 brok5 or %att]$ by dynamic action into mu* small] fragm5ts1 see ,fig4 #g1 %[+ cru%$ rim ( fragm5ts surr\nd+ feldsp> 8auge40 ,9 o!r cases an actual b5d+ or di/ortion ( ! cry/al has tak5 place1 & aga9 sometimes ! effect ( me*anical /ress is only %[n by ! s-call$ 8wavy0 ext9ction4 ,see p4 #ca & ,fig4 #g1 %[+ a c>lsbad tw9 ( feldsp> t has be5 b5t & !re=e %[s m>k$ 8wavy0 ext9ction4 ,illu/ration3 ,,fig4 #g4--,or?oclase 8auge0 7,c>lsbad tw971 %[+ b5d+ & 8wavy0 ext9ction1 surr\nd$ by cru%$ rim ( m9]al fragm5ts4 ,z se5 ) cross$ nicols4 8,aug5-gneiss10 ,b$=d1 ,n4 ,y4--,b4 #ac4 ,illu/ration3 ,,fig4 #h4--;,cry/allites & ,microlites a4 ,skeleton ,=ms b4 ,cry/allites1 9 g5]al ^? incipi5t =ms ( cry/als :i* h n yet rea*$ a /age ( developm5t suffici5t to %[ d\ble refraction1 see ,fig4 #h1 a4 ,q a numb] ( names are us$ to describe ! diff]5t =ms t occur4 ,microlites1 m or less completely def9$ microscopic cry/als1 :i* usually %[ d\ble refraction1 b _c be always specifically det]m9$1 see ,fig4 #h1 a4 ,skeleton ,=ms1 result+ f rapid cool+ ( ! magma occur 9 "s lavas1 see ,fig4 #h1 b4 7b7 ,color4 ,x mu/ be rememb]$ t ! colors obs]v$ are always due to transmitt$ light & may be call$ 8absorption t9ts40 ,m9]als :i* 9 h& specim5s are opaque are (t5 color$ 9 sections2 & m9]als :i* are commonly color$ may appe> colorless 9 sections4 ,at times color may be giv5 to a section simply by ! pres5ce ( a great numb] ( m9ute inclusions4 ,illu/ration3 ,,fig4 #i4--,oliv9e cry/al 9 basalt %[+ 8high relief0 & cleavage4 7c7 ,index ( ,refraction4 n s9 i_/s9 r4 ,?is c be approximately det]m9$ by ! appe>ance ( ! surface & outl9e ( a m9]al1 t is by its relief4 ,! descriptive t]ms are ( c\rse relative1 b 9 common practice m9]als are said to h m$ium refraction :5 ! refractive index is betwe5 t ( balsam 7#a4ed7 & t ( calcite 7#a4fj71 /rong refraction :5 high] ?an #a4fj & weak refraction :5 l[] ?an #a4ed4 ,9 ! case ( uniaxial & biaxial m9]als ! mean value ( ! indices ( refraction is us$4 ,a m9]al :i* has /rong refraction appe>s to h high relief1 i4 e41 di/9ct d>k cont\rs & a r\gh or 8%agre5$0 surface1#ca :i* has bright illum9ation & appe>s to /& out above ! surfaces ( ! surr\nd+ m9]als ) weak] refraction1 see ,fig4 #i4 ,a m9]al ) m$ium refraction does n %[ any relief1 h5ce has a smoo? surface & no d>k cont\rs1 see ,fig4 #e4 ,a m9]al ) weak refraction may also appe> to h a r\gh surface1 b n s m>k$ z 9 ! case ( a m9]al ) v /rong refraction1 due to ! small] contra/ 9 indices betwe5 ! m9]al & balsam4 ,! practical way ( te/+ = ! approximate index ( refraction or ! relief ( a m9]al is to make use ( ! l5s = conv]g5t light1 :i* is plac$ on top ( ! l[] nicol imm$iately bel[ ! section4 ,by l[]+#cb ! l5s ! "* ( ! relief ( a m9]al section is made v app>5t4 ,9 ord] to become famili> ) ! way 9 :i* ! 8relief0 or appe>ance ( ! surface indicates ! /r5g? ( ! refractive index1 ! /ud5t may use a long glass slide on :i* are emb$d$ 9 balsam 7#a4ed7 small fragm5ts ( diff]5t m9]als1 = example3 ,sodalite 7#a4dhc71 or?oclase 7#a4ebc71 qu>tz 7#a4edg71 topaz 7#a4fbj71 hornbl5de 7#a4fca71 augite 7#a4gj71 epidote 7#a4gea71 zircon 7#a4ie7 & rutile 7#b4gab74 ,det]m9ations ( refractive indices 9 sections by ! me?ods ( ,*aulnes1#cc ,sorby1#cd or total reflection are accompani$ by _m difficulties & may fail to give satisfactory results4 ,! ,becke me?od1 h[ev]1 (t5 furni%es a conv5i5t means ( det]m9+ ! relative values ( ! refractive indices ( adjo9+ m9]als or ( m9]als emb$d$ 9 balsam4 ,?is is ( especial s]vice :5 "o ( ! m9]als is kn[n & h5ce its refractive index4 ,,becke ,,me?od4#ce ,suppose two adjo9+ m9]als1 9 a ?9 rock section1 to be s+ly refract+ & to h _! plane ( contact v]tical1 i4 e41 p>allel to ! optic axis ( ! microscope4 ,let ,a & ,c1 ,fig4 #aj1 be two su* sections ) ! plane ( contact ,,oo v]tical1 ,a hav+ a l[] refractive index ?an ,c1 & consid] only ! direction ( ! rays )9 ! section1 neglect+ ! refractive effect ( ! air1 glass & balsam4 ,a beam ( transmitt$ light conta9s besides normal rays conv]g5t rays1 :i* pass ?r\gh ! section z indicat$ 9 ,fig4 #aj4 ,consid] n[ ! cone ( light rays ,,gbi4 ,! rays ,o,g on meet+ ! plane ( contact ,,oo w be some:at conc5trat$ & deflect$ by ! high] refractive index ( ,c & w cont9ue z ! cone ,,ef4 ,"s rays z ,o,h w1 on meet+ ! contact plane1 be totally reflect$ & w cont9ue z ! cone ,,oe1 :ile ! re/ ( ! rays ,,hi w be disp]s$ & deflect$ by ! weak] refractive index ( ,a1 cont9u+ z ! cone ,,od4 ,h5ce1 m light rays w em]ge on ! side ( ! contact plane :]e ! sub/ance ( high] refractive index lies1 & !re w be a conc5tration ( illum9ation on ?is side produc+ ! s-call$ 8bright l9e40 ,illu/ration3 ,,fig4 #aj4 ,9 practically mak+ ! te/ ) a petrographical microscope remove ! pol>iz]1 analyz] & cond5s+ l5s1#cf & introduce bel[ ! section a small light-/op1 to r$uce 9 size ! cone ( incid5t light4#cg ,! adapt]1 hold+ ?is light-/op1 %\ld be adju/able s t ! /op c be l[]$ suffici5tly to produce ! be/ results4 ,! small] ! contra/ betwe5 ! indices ( refraction ! small] ! incid5t cone ( light %\ld be1 z be/ results are obta9$ :5 ?is cone is little l>g] ?an twice ,o,h1 ,fig4 #aj1 all ! ,o,h rays be+ !n totally reflect$4 ,! m ( ! ,,hi rays t pass ?r\gh1 ! bright] w be ! ,,od cone & ! less %>p ! contra/ 9 illum9ation4 ,a high p[] objective#ch %\ld be us$1 z ^? ) small ap]ture & great focal l5g? d n give good results4 ,focus on ! divid+ plane & adju/ until equal illum9ation is obs]v$ on bo? sides & ! trace ( ! plane resembles a f9e ?read1 ! focal plane be+ at ,,mn4 ,!n raise ! objective slightly1 ?us mov+ ! focal plane to ,,/1 :5 a bright l9e or b& w appe> on ! side ( ! /rong] refract+ sub/ance1 ! wid? ( ! l9e dep5d+ on ! contra/ betwe5 n & n1 becom+ n>r[] z n & n approa* ea* o!r 9 value4 ,on rais+ ! objective /ill fur!r ! l9e broad5s & f9ally disappe>s4 ,if ! objective is l[]$ in/ead ( rais$ ! rev]se ph5om5on w take place1 ! bright l9e appe>+ on ! side ( ! weak] refract+ sub/ance4#ci ,:5 ! indices are ne>ly ! same a bright l9e w appe> on bo? sides & x is important !n to make ! cone ( incid5t light z small z possible & to select ! bright] l9e4 ,) d\bly refract+ m9]als1 ea* set ( d\bly refract$ rays w\ld suff] total reflection "u some:at diff]5t conditions & !re w\ld be no "o po9t ,b 7z 9 isotropic m9]als7 :]e no bright l9es w\ld appe>4 ,h[ev]1 if ! cone ( incid5t light is small en\gh 9 diamet]1 ! te/ w be practically obta9$ z describ$4 ,! ,becke te/ c (t5 be made ) a m$ium p[] objective#dj )\t remov+ ! pol>iz] & cond5s+ l5s1 provid$ ! cond5s+ l5s be l[]$ suffici5tly4 ,x may also prove conv5i5t to turn ! reflector a little sideways4 ,! ?9n] ! section ! m di/9ct w be ! ph5om5on4 ,! contact plane mu/ be cle> & n coat$ ) opaque decomposition products4 ,:5 ! plane ( contact ,,oo deviates consid]ably f p>allelism ) ! optic axis ( ! microscope a di/urbance ( ! ph5om5on may be expect$ & no satisfactory results be obta9$4 ,9 g5]al "u ^! conditions ! 8bright l9e10 bo? on rais+ & l[]+ ! objective1 w rema9 on ! side ( ! ov]lapp+ sub/ance1 )\t reg>d to ! relative values ( ! indices4 ,! refractive index ( ! cem5t+ mat]ial %\ld n be v mu* l[] ?an t ( ei!r ( ! ?9 sections1 z ! result w\ld !n be to disp]se ! em]g+ rays too mu* & dim ! effect4 ,9 ! case ( di/+ui%+ betwe5 m9]als ( high refractive p[]1 su* z augite & g>net1 me?yliodide is recomm5d$ in/ead ( balsam4 ,9 ! case ( d\bly refract+ cry/als1 ! l[] nicol 7pol>iz]7 mu/ be reta9$1 if x is desir$ to obta9 ! relative refractive index ( "o ( ! two rays1 ei!r ) respect to ! balsam or to a ray 9 an adjo9+ cry/al ) a p>allel vibration direction4 ,= det]m9+ vibration directions ( rays & ! fa/] & sl[] rays 9 two adjo9+ sections see lat]1 pp4 #ca & #cc4 ,! me?od ( ,s*rd] van d] ,kolk#da c also be employ$ = ! same purpose z ! ,becke te/4 ,! ord9>y objective 7,seib]t ,no4 ,,ii7 is us$1 & ! me?od ess5tially consi/s ( d>k5+ a portion ( ! field by means ( ! f+] or a plate ins]t$ bel[ ! pol>iz]4 ,! cond5s] l5s mu/ be l[]$ beyond ! %>p focus ( ! edge ( ! %ad[ 7on rais+ ! cond5s] ! foll[+ ph5om5a are rev]s$74 ,z ! %ad[ approa*es ! contact betwe5 two m9]als a bright l9e w appe> on ! edge ( ! 8f>0 m9]al1 if its refractive index is ! high]1 & a d>k l9e on ?is same edge if its index is l[] ?an t ( ! 8ne>0 m9]al4 ,! indices ( ! two rays 9 d\bly refract+ m9]als mu/ be det]m9$ by ! aid ( ! pol>iz]4 ,illu/ration3 ,,fig4 #aa4--;,biotite1 %[+ p]fect cleavage1 9 rhyolite4 7d7 ,cleavage1#db :i* appe>s z m or less di/9ct & regul> l9es or cracks1 see ,figs4 #aa & #ab4 ,^! cleavage cracks may be p>allel or int]sect1 dep5d+ on ! position ( ! section relative to ! cleavage planes ( ! cry/al4 ,illu/ration3 ,,fig4 #ab4--;,augite a1 %[+ good cleavage1 & plagioclase p 9 diabase4 ,! plagioclase %[s 8polysyn!tic0 tw9n+ betwe5 cross$ nicols4 ,illu/ration3 ,,fig4 #ac4--;,g>net 9 mica s*i/1 %[+ fracture4 ,franconia1 ,n4 ,y4 ,cleavage is sometimes be/ obs]v$ by slightly l[]+ ! cond5s+ l5s "u ! section4 ,:5 sections %[ int]sect+ cleavage cracks x is (t5 possible to recognize ! m9]al by its kn[n cleavage angle1 z 9 ! case ( amphibole & pyrox5e4 7e7 ,fracture1 :i* appe>s z irregul> & non-p>allel cracks1 see ,fig4 #ac4 ,illu/ration3 ,,fig4 #ad4--;,apatite 9 feldsp> a4 ,g>nets 9 qu>tz1 ,bran*ville1 ,ct41 b4 ,liquid inclusions ( ,,co#b1 "s %[+ gas bubbles1 9 qu>tz c4 ,illu/ration3 ,,fig4 #ae4--;,en/atite %[+ 8,s*ill]0 ,/ructure4 7f7 ,inclusions1 :i* may be solid 7ei!r di/9ct cry/als or glass71 fluid or gas1 see ,fig4 #ad4 ,^! inclusions are di/+ui%$ by ! fact t ! solid inclusions g5]ally h %>p cont\rs1 ! fluid inclusions di/9ct d>k bord]s1 & ! gas inclusions broad d>k bord]s m di/9ctly m>k$ ?an ^? ( ! fluid inclusions4 ,! fluid inclusions (t5 conta9 a bubble ( gas4 ,! inclusions may h a def9ite or indef9ite position 9 ! cry/al 9 :i* !y occur1 & c sometimes be m di/9ctly se5 by us+ conv]g5t light or a 8spot0 l5s4 7g7 ,s*ill] ,/ructure4 8,is t 9 :i* cavities ( def9ite =m & ori5tation 7#8negative cry/als'7 are develop$ along c]ta9 planes & fill$ or p>tially fill$ by mat]ial dissolv$ out ( ! enclos+ cry/al10#dc see ,fig4 #ae4 ,*>act]s ,obs]v$ by ,pol>iz$ ,light4 ,! pol>iz$ light is obta9$ by pass+ ! beam ( light f ! reflector ?r\gh ! pol>iz] or l[] nicol1#dd :i* mu/ be 9 place bel[ ! /age ( ! microscope4 ,:ite light is suppos$ to be us$4 ,pleo*roism1 t prop]ty :i* all anisotropic m9]als h1 to a great] or less ext5t1 ( absorb+ c]ta9 color$ rays 9 c]ta9 directions1 !reby %[+ diff]5t colors 9 diff]5t directions by transmitt$ light4 ,uniaxial m9]als are di*roic %[+ two diff]5ces 9 color1 produc$ by ! rays :i* vibrate p>allel to ! direction ( ! v]tical axis & ! plane ( ! basal axes4 ,biaxial cry/als are tri*roic %[+ !oretically ?ree diff]5ces ( color produc$ by rays ) vibration directions correspond+ v ne>ly to ^? ( ! ?ree pr9cipal vibration directions4#de ,any giv5 section ( a biaxial cry/al w1 ( c\rse1 appe> only di*roic4 ,! practical way ( te/+ = pleo*roism is z foll[s3 ,revolve ! /age1 c>ry+ ! section1 :5 a *ange 9 ! color ( ! m9]al w be notic$1 if x is pleo*roic4 ,?is pleo*roism may appe> z an actual *ange 9 color or simply z a *ange 9 ! %ade ( ! same color4 ,at times x may be s weak z h>dly to be notic$1 :5 x is be/ to make ! te/ ) ! cond5s+ l5s 9 position imm$iately "u ! section1 or by rotat+ ! l[] nicol in/ead ( revolv+ ! /age4 ,! color ( ! light1 vibrat+ p>allel to c]ta9 def9ite cry/allographic directions 9 m9]als1 is (t5 v *>act]i/ic4 ,9 "s cases !re may be su* /rong absorption ( "o ( ! rays1 t1 :5 ! vibration direction ( ?is ray is ov] ! plane ( vibration ( ! pol>iz]1 practically no light is transmitt$ & ! section appe>s d>k4 ,/rong absorption is *>act]i/ic ( c]ta9 m9]als1 su* z biotite1 amphibole1 t\rmal9e & allanite & takes place p>allel to def9ite directions 9 ^! m9]als4 ,pleo*roism may (t5 be notic$ ) ord9>y light 9 ! case ( h& specim5s4 ,*>act]s ,obs]v$ ) bo? ,pol>iz] & ,analyz]#df 9 ,position1 t is ) 8,cross$ ,nicols40 ,:5 ! nicols are accurately cross$1 ! field %\ld be q d>k1 & if ?is is n ! case ! adju/m5ts mu/ be look$ to4 ,! cond5s+ l5s %\ld be remov$ = ^! te/s z !y are to be made ) p>allel light1 b z a matt] ( conv5i5ce in/ead ( remov+ ! cond5s+ l5s1 ! pol>iz] ) ! l5s on top may be l[]$1 :5 ! results w be ab\t ! same z ) p>allel light4 ,:ite light is suppos$ to be us$4 ,isotropic ,"*4 ,sections ( isotropic cry/als are p]fectly d>k & rema9 s dur+ a complete rotation ( ! /age ?r\gh #cfj4 ,! explanation is v simple4 ,light be+ transmitt$ by an isotropic cry/al 9 all directions )\t d\ble refraction2 x foll[s t ! light f ! pol>iz]1 aft] hav+ pass$ ?r\gh ! section1 comes to ! analyz] /ill vibrat+ 9 ! plane ( vibration ( ! pol>iz]4 ,h5ce x is entirely cut out by ! analyz]4 ,amorph\s transp>5t sub/ances act 9 ! same way & rema9 d>k dur+ complete rotation ( ! /age4 ,optical anomalies1 i4 e41 d\ble refraction1 may occur 9 isometric cry/als & 9 amorph\s sub/ances t h be5 subject$ to /ra9s4 ,anisotropic ,"*4 ,sections ( anisotropic cry/als1 hav+ ! prop]ty ( d\ble refraction1 produce 9 g5]al "s int]f]5ce or pol>ization color1 except z m5tion$ lat]4 ,! popul> explanation is z foll[s3 ,illu/ration3 ,,fig4 #af4 ,9 ,fig4 #af1 let ,,pp be ! plane ( vibration ( ! pol>iz]1 & ,a,a ! plane ( vibration ( ! analyz]4 ,all ! light1 aft] x has pass$ ?r\gh ! pol>iz]1 is vibrat+ p>allel to ,,pp :5 x rea*es ! l[] side ( ! transp>5t cry/al1 cdef1 on ! /age ( ! microscope4 ,9 ?is transp>5t section let ob & oa be ! two directions ( vibration1 i4 e41 ! only two directions p>allel to :i* rays ( light c vibrate 9 pass+ ?r\gh ! section4 ,let om repres5t ! amplitude ( vibration ( a ray f ! pol>iz]4 ,:5 ?is ray rea*es ! section x _c get ?r\gh x vibrat+ 9 ! direction om1 b is d\bly refract$ & ( ! two result+ rays1 "o gets ?r\gh vibrat+ 9 ! direction ob & ! o!r vibrat+ 9 ! direction oa4 ,f m draw p]p5dicul>s to ob & oa4 ,!n accord+ to ! law ( ! p>allelogram ( =ces ob w repres5t ! amplitude ( vibration ( ! ray pass+ ?r\gh ! cry/al vibrat+ 9 ! direction ob1 & oa w repres5t ! amplitude ( vibration ( ! ray pass+ ?r\gh ! cry/al vibrat+ 9 ! direction oa4 ,we w ?us h two rays pass+ ?r\gh ! cry/al1 pol>iz$ at "r angles to ea* o!r4 ,illu/ration3 ,,fig4 #ag4 ,consid] n[ ! g5]al "q ( ! transmission ( ! d\bly refract$ rays ?r\gh a plate4 ,:atev] ! angle ( ! p>allel incid5t rays1 ea* ray z ,,ab1 ,fig4 #ag1 is resolv$1 z j describ$1 into two rays ,,bc & ,,bd1 pol>iz$ at "r angles to ea* o!r & foll[+ 7usually7 diff]5t pa?s 9 ! plate4 ,on em]g5ce ^! foll[ p>allel pa?s4 ,among ! incid5t rays !re are rays ,,eg & ,,fh1 su* t "o compon5t ( ,,fh w em]ge at ,d ) "o ( ! compon5ts ( ,,ab1 & "o compon5t ( ,,ab & "o compon5t ( ,,eg w em]ge at ,c4 ,h5ce f e po9t ( ! upp] surface ( ! plate !re w em]ge two rays & ^! rays w h travell$ ?r\gh diff]5t pa?s 9 ! plate ) diff]5t velocities & w h _! vibrations at "r angles to ea* o!r4 ,:5 ^! d\bly refract$ rays come to ! analyz]1 ^: plane ( vibration is ,a,a1 !y _c get ?r\gh vibrat+ 9 _! pres5t directions1 b compon5ts ( ^! rays1 su* z ot & os1 c get ?r\gh vibrat+ p>allel to ! plane ,a,a4 ,h5ce we h two s]ies ( rays com+ to ! eye1 pol>iz$ 9 ! same plane1 b "o set slightly 9 advance ( ! o!r4 ,^! rays w 8int]f]e0 & produce "s int]f]5ce or pol>ization color4#dg ,9 us+ :ite light :5ev] "o ( two light rays ( ! same color has suff]$ a 8ret>dation0 ( j "o wave-l5g? 7or ev5 multiple !re(7 ! color w be ext+ui%$2 & :5 ! 8ret>dation0 is "o half wave-l5g? 7or ev5 multiple !re(7 ! color w be int5sifi$4 ,!re=e1 "s t9ts w be ext+ui%$ & o!rs int5sifi$1 ! comb9ation result+ 9 ! production ( "s def9ite int]f]5ce color4 ,( c\rse 9 ! case ( mono*romatic light ! ?ickness ( ! section may be su* t 8de/ructive int]f]5ce0 takes place produc+ no color 7d>kness74 ,n[ suppose ! /age to be rotat$ until ! section cdef takes ! position cdef4 ,! section w be f\nd to be d>k & no int]f]5ce color w be se54 ,?is is due to ! fact t ! directions ( vibration 9 ! section are p>allel to ! planes ( vibration ( ! cross$ nicols1 consequ5tly ! light passes ?r\gh ! section /ill vibrat+ p>allel to ! plane ,,pp ( ! pol>iz] & is all cut out by ! analyz]4 ,d>kness w occur e #ij & !re=e f\r times dur+ a complete rotation ( ! /age4 ,! int]f]5ce color is also obs]v$ to v>y 9 int5sity1 b n 9 color1 & to be at its maximum #de f ! positions ( d>kness4 ,sections ( uniaxial cry/als at "r angles to ! optic axis act l isotropic sub/ances & rema9 d>k dur+ a complete rotation ( ! /age4 ,9 ! biaxial cry/als1 a section at "r angles to an 8optic axis0 %[s uni=m illum9ation#dh :i* does n *ange z ! /age is rotat$4 ,! only way to f9d out :e!r sections t rema9 d>k are isotropic1 or uniaxial at "r angles to an optic axis1 is to te/ !m ) conv]g5t light z describ$ lat]1 see p4 #dj4 ,int]f]5ce ,colors4 ,! int]f]5ce color %[n by any m9]al section dep5ds on ?ree factors3 #a ! /r5g? ( ! d\ble refraction 7 ! diff]5ce betwe5 ! refractive indices ( ! sl[e/ & fa/e/ rays72 #b ! position ( ! section 9 ! cry/al2 #c ! ?ickness ( ! cry/al section4 ,to elim9ate1 s f> z possible1 ! v>iation due to ! optical ori5tation ( ! section1 c>e mu/ always be tak5 to obta9 ! maximum int]f]5ce color giv5 by ! diff]5t sections ( ! same m9]al 9 ! rock section4 ,sections giv+ ! maximum color are ^? p>allel to ! axis 9 uniaxial m9]als & ^? p>allel to ! axial plane 9 biaxial m9]als4#di ,h5ce su* sections 9 conv]g5t light nev] %[ ! em]g5ce ( an optic axis or a bisectrix2 & fur!rmore1 o!r clues1 su* z cry/al outl9es1 cleavage1 pleo*roism1 etc41 may help to indicate ! favorable section4 ,! influ5ce ( ! ?ickness ( ! section is also important & mu/ be consid]$4 ,! int]f]5ce color w rise 9 ! scale 7be high] 9 ord]7 z ! section becomes ?ick]4 ,me?ods ( obta9+ ! ?ickness ( a section are giv5 on pp4 #ce & #cf4 ,:5 ref]5ce is made to def9ite int]f]5ce colors ! m9]al section is suppos$ to h a ?ickness ( #j4jc mm4 & to be su* z to give ! maximum color2 & all m9]al sections 9 a rock section are consid]$ to h a uni=m ?ickness4 ,) ^! precautions 9 m9d ! int]f]5ce colors indicate ! /r5g? ( ! d\ble refraction z foll[s3#ej ,! colors ( m9]als ) v weak d\ble refraction v>y f a blui%-gray to a grayi%-:ite4 ,z ! /r5g? ( ! d\ble refraction increases ! colors become ! v int5se bright t9ts ( ! spectrum1 yell[1 r$1 blue1 gre51 etc41 call$ ! fir/ & second ord] colors4 ,z ! /r5g? ( ! d\ble refraction /ill increases ! colors pass ?r\gh ! t9ts ( ! spectrum 9 sequ5ce 7call$ ord]s71 becom+ pal] until f9ally1 :5 ! d\ble refraction is v /rong1 ! colors become ! neutral1 almo/ colorless t9ts ( ! high] ord]s4 ,! eye mu/ be tra9$ to appreciate ! colors ( diff]5t ord]s1 & ! /ud5t is advis$ to practice ) m9]al sections1 ( kn[n /r5g? ( d\ble refraction1 & comp>e ! result+ int]f]5ce colors ) a color *>t1#ea or use ! int]f]5ce color diagram at ! end ( ! book4 ,a conv5i5t te/ c be made ) a "o f\r? undulation mica plate to di/+ui% betwe5 ! :ite ( ! #a ord] & ! practically :ite v high ord] t9t4 ,introduce ! mica plate 9 ! slot k1 ,fig4 #b1 & ! effect w be to produce a m>k$ *ange 9 ! color ( ! #a ord]1 :ile no *ange w be obs]v$ 9 ! high ord] color4 ,! exact ord] ( ! color c be det]m9$ by ! use ( a qu>tz w$ge1 z describ$ on p4 #ce4 ,abnormal ,int]f]5ce ,colors#eb may be br\ght ab\t 9 sev]al ways4 ,9 :ite light /rong absorption ( "p ( ! light compon5ts may n only alt] ! color ( ! m9]al b also modify ! int]f]5ce color4 ,! d\ble refraction may be ne>ly z]o = light ( a p>ticul> color s t ! m9]al is isotropic = t color1 result+ 9 a *ange 9 ! int]f]5ce color1 z = example ! indigo ( melilite1 :i* is ne>ly isotropic = yell[ light4 ,9 biaxial m9]als ! axial angle may be z]o = light ( a p>ticul> color1 result+ also 9 a modification ( ! int]f]5ce color1 z ! blue 9 p5n9ite 9 sections ,bxa4 ,:5 ! bisectrices are mu* disp]s$ !re w be no position ( d>kness betwe5 cross$ nicols 9 :ite light4 ,ext9ction & ,ext9ction ,angles4 ,:5 ! section1 see ,fig4 #af1 is 9 su* a position t its directions ( vibration are p>allel to ! planes ( vibration ( ! nicols1 no light c pass ?r\gh ! analyz]1 & ! section is d>k4 ,h5ce ! light is ext+ui%$ & ?is ph5om5on is call$ ext9ction4 ,ext9ction is said to be p>allel or symmetrical :5 ! directions ( vibration are p>allel to any cry/allographic l9es or directions1 or bisect ! angles betwe5 ^! l9es4 ,! cry/allographic l9es or directions may be ei!r cleavages or ! simil> b\nd>ies ( idiomorphic cry/als4 ,?is k9d ( ext9ction is %[n by all sections ( tetragonal & hexagonal cry/als1 by all sections p>allel to ! cry/al axes 9 or?orhombic cry/als & also by ! sections p>allel to ! axis 9 monocl9ic cry/als4 ,:5 ! ext9ction is n symmetrical x is call$ oblique1 & is %[n by all sections ( monocl9ic cry/als 7except ^? p>allel to ! axis7 & tricl9ic cry/als4 ,ext9ction :i* does n take place ov] ! :ole ( ! section ( a s+le cry/al at ! same mom5t1 b passes ov] ! section l a d>k wave or %ad[1 is said to be 8wavy02 & indicates t ! cry/al has be5 subject$ to me*anical =ces produc+ a *ange 9 ! position ( ! directions ( vibration 9 diff]5t p>ts ( ! cry/al1 see ,fig4 #g4 ,! angle betwe5 a direction ( vibration 9 ! section & "s kn[n cry/allographic direction 7z a cleavage or cry/al outl9e7 is call$ an ext9ction angle1 & is measur$ 9 ! foll[+ way3 ,f9d ! positions ( ! directions ( vibration 9 ! section1 :i* mu/ be p>allel to ! cross-wires :5 ext9ction takes place4 ,note ! read+ on ! graduat$ circle ( ! /age1 !n remove ! upp] nicol1 9 ord] to get a m di/9ct view ( ! field1 & rotate ! /age until y br+ "s kn[n cry/allographic l9e into p>allel position ) ! cross-wire select$ z a ref]5ce l9e4 ,take ! read+ ( ! graduat$ circle aga91 & ! diff]5ce betwe5 ^! two read+s w be ! ext9ction angle4 ,x c readily be se5 t dep5d+ on :i* way ! section is rotat$1 ei!r a small or a l>ge ext9ction angle w be obta9$1 ! two angles be+ complem5ts ( ea* o!r4 ,! ext9ction angle g5]ally record$ is t betwe5 ! ne>e/ direction ( vibration & ! v]tical axis 4 ,9 monocl9ic m9]als ! maximum value ( ! ext9ction angle 7! angle ( real value 9 di/+ui%+ ! m9]al7 c only be obta9$ f a section p>allel to ! cl9o p9acoid 7#jaj72 b 9 practice suffici5tly accurate results c g5]ally be obta9$ by measur+ ! ext9ction angles ( all sections ( ! same m9]al1 :i* seem to be ab\t p>allel to ! v]tical axis 1 & !n tak+ ! maximum value obta9$4 ,amphibole & pyrox5e c easily be di/+ui%$ 9 ?is way4 ,ext9ction is g5]ally te/$ = by revolv+ ! /age1 c>ry+ ! section1 until d>kness is obs]v$4 ,! pr9cipal difficulty1 h[ev]1 is caus$ by ! eye fail+ to appreciate ! position ( maximum d>kness4 ,h5ce x is bett] to revolve ! /age until ! section j becomes d>k 7or fades out7 & !n revolve fur!r until ! section j beg9s to light5 up aga94 ,! mean ( ! read+s1 9 ^! two positions1 w be ! "o to use4 ,a gypsum te/-plate1 s prep>$ z to give "s def9ite int]f]5ce color1 z r$ ( ! #a ord]1 may be introduc$ betwe5 ! two nicols1 & ! section revolv$ until ?is color is exactly mat*$4 ,?is p]fect mat*+ ( color is only possible :5 ! directions ( vibration ( ! section are exactly p>allel to ! planes ( vibration ( ! nicols1 z o!rwise "s int]f]5ce color w\ld be produc$ by ! section & ! true color ( ! te/-plate w\ld n appe>4 ,! mo/ favorable condition is :5 ! section is colorless & only cov]s a "p ( ! field ( view1 z !n ! re/ ( ! field %[s ! color ( ! te/-plate & ! exact mat*+ ( color is an easy matt]4 ,?is me?od ( te/+ c be employ$ to recognize ! v weak d\ble refraction ( "s m9]als1 ^: int]f]5ce colors are su* d>k grays z n to be notic$ )\t ?is te/4 ,aft] ! te/-plate has be5 introduc$1 "s slight v>iation 9 ! color w be obs]v$ :5 ! /age c>ry+ ! d\bly refract+ section is rotat$4 ,!re are o!r me?ods#ec = locat+ ^! directions ( vibration4 ,!y dep5d g5]ally on sub/itut+ *anges ( color = degrees ( d>kness or on *anges 9 int]f]5ce figures1 & consi/ 9 ! use ( color te/-plates or ,kle9's qu>tz-plate1 or ( special ocul>s prep>$ by ,b]tr&1 ,cald]on1 etc4 ,,me?od ,,( ,,te/+ ,,= ,,! ,,vibration ,,directions ,,( ,,! ,,fa/] ,,& ,,sl[] ,,rays1 ,a ,,& ,c1 ,,9 ,a ,,m9]al ,,section4 ,a mica or gypsum plate c be us$ to make ?is te/1 ! directions ( vibration ( ! fa/] & sl[] rays on ^! plates be+ kn[n & m>k$4#ed ,! cry/al section to be te/$ is plac$ on ! rotat+ /age1 betwe5 cross$ nicols1 & turn$ to ! position ( ext9ction1 :5 ^! directions ( vibration w be p>allel to ! cross-wires 9 ! eye-piece4 ,! section is !n turn$ #de1 :5 ! int]f]5ce color w be at its maximum1 & ^! directions ( vibration w make angles ( #de ) ! planes ( vibration ( ! nicols & ! cross-wires 9 ! eye-piece4 ,n[ introduce#ee ! te/-plate1 betwe5 ! section & ! analyz]1 s t its kn[n directions ( vibration also make angles ( #de ) ! cross-wires 9 ! eye-piece4 ,:5 ! te/-plate is introduc$ a new int]f]5ce color w be notic$ :i* is ei!r high] or l[] 9 ! color scale#ef ?an ! orig9al int]f]5ce color ( ! m9]al section4 ,:5 ! kn[n directions ( vibration ( ! te/-plate are sup]pos$ ov] correspond+ directions 9 ! m9]al section1 ! effect is to ?ick5 ! section & ! int]f]5ce color rises 9 ! scale4 ,:5 ! directions ( vibration ( ! te/-plate are sup]pos$ ov] directions ( vibration 9 ! m9]al section :i* are n correspond+1 ! effect is to ?9 ! section & ! int]f]5ce color s9ks 9 ! scale4 ,= m9]als :i* h v /rong d\ble refraction1 z zircons1 s t ! int]f]5ce colors are ( ! high] ord]s1 x is advisable to use ! me?od ( te/+ ) a qu>tz w$ge4#eg ,if a w$ge is ins]t$ betwe5 cross$ nicols & its c direction incl9$ at #de to ! planes ( vibration ( ! nicols1 !n successive int]f]5ce colors w be se5 comm5c+ ) ! gray ( ! fir/ ord] & pass+ ?r\gh ! colors z %[n by a color *>t4 ,if n[ ! cry/al section lies ) its vibration directions also 9 ! diagonal position1 ! color ( any portion ( ! qu>tz w$ge w be *ang$ :]e x cov]s ! section1 ! new color be+ t ( a ?ick] "p ( ! w$ge if ! c direction 9 ! section lies "u ! c direction ( ! w$ge4 ,also :]e ! w$ge ov]laps ! section ! displacem5t ( ! color fr+es 9 ! section w be t[>ds ! ?9 edge ( ! w$ge4 ,on ! o!r h& ! new color w be t ( a ?9n] "p ( ! w$ge :5 ! a direction 9 ! section lies "u ! c direction ( ! w$ge4 ,9 ?is case ! displacem5t ( ! color fr+es w be t[>ds ! ?ick "p ( ! w$ge4 ,?is me?od is v conv5i5t :5 ! cry/al section has 9 any place slop+ edges1 %[+ prismatic color fr+es4 ,! movem5t ( ^! fr+es 7z previ\sly describ$7 is t[>ds ! ?9 edge ( ! w$ge :5 ! vibration directions correspond & away f ?is edge :5 !y d n correspond4 ,if ! w$ge :5 ins]t$ f9ally 8comp5sates0 ! color ( ! cry/al section 7i4 e41 practically produces an abs5ce ( color1 d>kness71 !n ! a 9 ?is section mu/ lie "u ! c 9 ! w$ge1 z ! effect ( ! w$ge has be5 to cont9ually ?9 ! section4 ,,det]m9ation ,,( ,,ord] ,,( ,,int]f]5ce ,,color4 ,?is c be det]m9$ by use ( a qu>tz w$ge or a v4 ,f$][ mica w$ge4#eh ,h ! vibration directions ( ! giv5 section 9 ! diagonal position1 !n gradually ins]t ! w$ge betwe5 ! cross$ nicols s t ! correspond+ vibration directions 9 ! section & w$ge are cross$1 t is s t ! colors are run d[n until f9ally d>k gray or black is obta9$4 ,c\nt ! numb] ( times ! orig9al int]f]5ce color reappe>s1 if n times1 !n ! color is a r$1 blue1 gre51 etc41 ( n #a ord]4#ei ,x is (t5 easi] to ins]t ! w$ge until comp5sation ( ! color is obta9$2 !n z ! w$ge is pull$ out ! direct c\nt ( ! recurr5ce ( ! orig9al color w give ! ord] ( t color4 ,,me?od ,,( ,,measur+ ,,! ,,/r5g? ,,( ,,! ,,d\ble ,,refraction ,,by ,,von ,,f$][ ,,mica ,,w$ge4#fj 8,! w$ge#fa consi/s ( fifte5 sup]pos$ qu>t] undulation mica plates1 ea* ab\t two mm4 %ort] ?an ! "o b5ea? x & ) _! directions ( vibration p>allel4 ,! s]ies is m\nt$ on a /rip ( glass & cov]$ ) a cov]-glass4 ,! wave-l5g? ( a middle color may be tak5 z #efj 7million?s ( a millimet]72 h5ce ea* qu>t] undulation mica plate may be consid]$ to possess a phase diff]5ce or ret>dation ( #adj 4 ,if1 !n1 betwe5 ! pol>iz] & analyz] we ins]t ! mica w$ge1 s t its direction ( vibration ( ! sl[] ray1 c1 is at "r angles to t ( ! m9]al "u exam9ation1 we subtract f ! phase diff]5ce ( ! m9]al an am\nt equal to n times #adj 1 9 :i* n repres5ts ! numb] ( sup]pos$ mica plates 9 ! field4 ,:5 ! m9]al appe>s d>k ! value evid5tly corresponds closely to ! phase diff]5ce ( ! m9]al4#fb ,f ! expression e,x1 9 :i* is ! phase diff]5ce or ret>dation1 ,x ! d\ble refraction1 & e ! ?ickness 9 million?s ( millimet]s1 ! ?ickness c be d$uc$ :5 ! d\ble refraction is kn[n or vice v]sa4 ,if a m9]al ( kn[n d\ble refraction c be f\nd 9 ! section ne> ! m9]al "u inve/igation1#fc ! d\ble refraction ( ! latt] c be d$uc$ by measur+ ! phase diff]5ce ( ! kn[n m9]al1 :5ce e results1 & ?is sub/itut$ 9 ! above =mula yields ,x40 ,,me?od ,,( ,,det]m9+ ,,m9]als ,,& ,,?ickness ,,( ,,section1 ,,by ,,use ,,( ,,table ,,( ,,d\ble ,,refraction 7,,maximum7 ,,& ,,diagram4#fd ,select "s easily recogniz$ m9]al 9 ! rock section & note ! maximum int]f]5ce color giv5 by any ( its sections4#fe ,! /r5g? ( ! d\ble refraction ( ?is m9]al be+ kn[n1 look up on ! diagram ! diagonal l9e correspond+ to ?is d\ble refraction & foll[ along ?is l9e t[>d ! left h& l[] corn] until ! obs]v$ int]f]5ce color is rea*$1 :5 ! horizontal l9e w indicate ! ?ickness ( ! section4 ,! ?ickness is giv5 9 hundr$?s ( millimet]s4 ,!n 9 ! case ( ! unkn[n m9]al pick out ! section giv+ ! highe/ int]f]5ce color & c>ry along ! same horizontal l9e until ?is new color is locat$1#ff !n pass up to ! "r along ! diagonal l9e to ! numb]s indicat+ ! /r5g? ( ! d\ble refraction ( ! unkn[n m9]al4 ,turn to ! table :]e ! m9]als w be f\nd hav+ ab\t ?is /r5g? ( d\ble refraction4 ,example3 ,9 a section ( granite 7biotite-granite7 a gra9 ( qu>tz 0 select$1 :i* gave ! brighte/ color4 ,?is color 0 a bright yell[i% :ite & ! kn[n d\ble refraction ( qu>tz is #j4jji4 ,foll[+ d[n on ?is diagonal l9e until ! int]f]5ce color 0 rea*$ x 0 se5 t ! ?ickness ( ! section 0 ab\t #j4jc mm4 7a v ?9 section74 ,! section ( ! undet]m9$ m9]al1 giv+ ! highe/ ord] color1 %[$ a bright #b ord] purple-blue4 ,pass+ along ! #j4jc horizontal l9e until ?is color 0 rea*$ & !n up along ! diagonal l9e1 x 0 se5 t ! d\ble refraction ( ?is m9]al mu/ be ab\t #j4jd4 ,! table gives muscovite & g]ite z hav+ ab\t ?is d\ble refraction4 ,! m9]al 0 prov$ to be muscovite by its abs5ce ( color & relief & by ! *>act]i/ic cleavage & p>allel ext9ction4 ,illu/ration3 ,,fig4 #ah4--,sanid9e cry/al f1 %[+ ,c>lsbad tw9 7:i*1 z x consi/s ( two p>ts only1 may be call$ simple71 & qu>tz q 9 rhyolite4 ,cross$ nicols4 ,/ructure3 7a7 ,tw9n+1 g5]ally notic$ by ! p>ts ( ! tw9 n ext+ui%+ at ! same "t4 ,x may also be obs]v$1 )\t cross$ nicols1 j z 9 ! case ( macroscopic m9]als4 ,tw9n+ may be describ$ z3 simple1 ,fig4 #ah2 polysyn!tic1 due to repeat$ tw9n+ aft] ! same law1 ,fig4 #ab2 & cross$ or 8gridiron10 due to repeat$ tw9n+ aft] two laws1 ,fig4 #ai4 ,illu/ration3 ,,fig4 #ai4--,microcl9e1 %[+ cross$ or 8gridiron0 tw9n+4 ,cross$ nicols4 7b7 ,zonal /ructure1 (t5 only made visible by ! zones ext+ui%+ at diff]5t times4 ,x may1 h[ev]1 be notic$ by ! zones be+ ( slightly diff]5t color1 or by ! zonal di/ribution ( inclusions4 ,9 ! case ( ! feldsp>s ! zonal /ructure may be caus$ ei!r by ! cry/al be+ =m$ ( zones ( diff]5t *emical composition 7! successive zones 9 ! plagioclases gr[+ m acid t[>ds ! ext]ior71 or by ultra-microscopic tw9n+1#fg ,fig4 #bj4 ,illu/ration3 ,,fig4 #bj4--,zonal feldsp> 7,c>lsbad tw97 9 tra*yte4 ,cross$ nicols4 7c7 ,aggregate /ructure1 be+ a confus$ mass ( sep>ate little cry/als1 scales or gra9s all ext+ui%+ at diff]5t times1 ,fig4 #ba4 ,illu/ration3 ,,fig4 #ba4--,sphrulites 9 felsite4 ,gr\nd mass %[s aggregate /ructure4 ,cross$ nicols4 7d7 ,sphrulitic /ructure1 produc$ by ! aggregation1 9 a radiate =m1 ( cry/als or cry/allites4 ,x is g5]ally easily p]ceiv$ by ! d>k cross1 result+ f ! ext+ui%+ ( ! light 9 ^? cry/als ^: directions ( vibration are p>allel to ! planes ( vibration ( ! nicols4 ,:5 ! /age is revolv$ ! arms ( ! cross d n rotate1 ,fig4 #ba4 ,illu/ration3 ,,fig4 #bb4--,oliv9e decompos$ to s]p5t9e4 ,! pseudomorphism has be5 almo/ complete1 only small portions ( ! orig9al oliv9e rema9+4 ,! outl9e ( ! p>5t cry/al c be q di/9ctly se54 ,cross$ nicols4 7e7 ,pseudomorphic /ructure1 :i* may be p>tial or complete & is notic$ by ! *ang$ portions produc+ diff]5t optical effects f ^? ( ! orig9al m9]al4 ,sometimes1 al?\gh ! pseudomorphism has be5 almo/ complete1 ! =m ( ! orig9al m9]al or cry/al may /ill be se51 ,fig4 #bb4 ,*>act]s ,obs]v$ by ,conv]g5t ,pol>iz$ ,light4 ,conv]g5t light is obta9$ by pass+ ! rays ( pol>iz$ light ?r\gh a /rong cond5s+ l5s1 :i* g5]ally fits l a cap ov] ! top ( ! pol>iz]4 ,by means ( a suitable adju/m5t ! cond5s+ l5s c be br\ght v close to ! l[] surface ( ! section on ! /age4 ,! l5s ?us s5ds a cone ( light ?r\gh ! section1 & us$ 9 connection ) cross$ nicols a s]ies ( optical ph5om5a1 call$ int]f]5ce figures1#fh are produc$4 ,ea* direction 9 :i* rays are s5t is trav]s$ by a m9ute bundle ( p>allel rays & ^! rays ext+ui% & produce int]f]5ce colors z already describ$ = p>allel light4 ,h5ce ea* direction yields a spot or picture 9 ! field ( view & f all ^! spots comb9$ !re results an 8int]f]5ce figure0 or picture1 dep5d+ ^u ! /ructure ( ! section = all ! directions trav]s$ by ! rays4 ,a v high p[] objective#fi mu/ be us$1 & :5 ! eye-piece is remov$1 a small image ( ! int]f]5ce figure w be se54 ,9 "s microscopes an arrangem5t is made = gett+ a magnifi$ image ( ! int]f]5ce figure1 by reta9+ ! eye-piece & us+ an additional ,b]tr& l5s4 ,9 ord] to get good results c>e mu/ be tak5 to h /rong illum9ation & ! cond5s+ l5s close up "u ! section4 ,! te/s are be/ made ) mono*romatic light1 b ) :ite light ! effects are sub/antially ! same1 ! only diff]5ce be+ t ! r+s & curves are v>i\sly color$ in/ead ( be+ simply light & d>k4 ,isotropic sub/ances %[ no int]f]5ce figures4 ,uniaxial ,int]f]5ce ,figures4 7a7 ,sections p]p5dicul> to ! optic or v]tical axis %[ a d>k cross1 ) or )\t color$ r+s1 ,figs4 #bc & #bd4 ,! figure is symmetrical to ! c5t]1 z ! optical behavior ( uniaxial cry/als is symmetrical to ! optic axis4 ,illu/ration3 ,,fig4 #bc4 ,illu/ration3 ,,fig4 #bd4 ,! arms ( ! cross are p>allel to ! planes ( vibration ( ! nicols1 & ! figure does n move :5 ! /age c>ry+ ! section is rotat$4#gj 7b7 ,sections oblique to ! optic axis %[ a portion ( a d>k cross1 ) or )\t color$ r+s1 ,fig4 #be4 ,! c5tre ( ! cross is n 9 ! axis ( rotation1 & z ! /age be>+ ! section is revolv$1 ! c5tre ( ! cross describes a circle1 ! arms always ma9ta9+ p>allel positions4 ,if ! section is /ill m oblique to ! optic axis ! c5tre ( ! int]f]5ce cross may be outside ! field ( view1 & only portions ( ! d>k arms w be se54 ,sections p>allel to ! optic axis %[ a vague d>k cross1 :i*1 on rotat+ ! /age1 dissolves into hyp]bolic curves 7sugge/+ biaxial figure71 :i* v rapidly disappe> 9 ! direction ( ! optic axis4 ,:5 ! int]f]5ce figure %[s colors1 ^! colors are l[] 9 ord] 9 ! quadrants conta9+ ! optic axis4 ,kn[+ ?us ! position ( ! optic axis ! optical "* c be obta9$ by ! me?od = p>allel light1 p4 #dc4 ,illu/ration3 ,,fig4 #be4 ,sections :i* are ?ick & h /rong d\ble refraction w %[ ! cross & r+s cle>ly & %>ply def9$1 !re be+ q a numb] ( r+s cr[d$ close toge!r4 ,sections :i* are v ?9 & h weak d\ble refraction %[ only a broad d>k cross & no r+s4 ,! int]f]5ce figures w v>y betwe5 ^! extremes1 dep5d+ on ! ?ickness ( ! section & ! /r5g? ( ! d\ble refraction4 ,to obta9 ! mo/ *>act]i/ic figures1 obs]vations mu/ be made on sections ab\t p]p5dicul> to ! optic axis1 t is sections :i* rema9 d>k or ne>ly d>k dur+ complete rotation betwe5 cross$ nicols 9 p>allel light4 ,optical ,"*1 ,positive or ,negative4 ,aft] hav+ obta9$ an uniaxial int]f]5ce figure1 te/ x by means ( a undulation mica plate4 ,?is plate mu/ be introduc$ betwe5 ! objective#ga & ! analyz] 9 su* a way t its vibration direction c1 m>k$ on ! plate1 makes an angle ( #de ) ! planes ( vibration ( ! nicols4 ,:5 ?is is done ! int]f]5ce figure *anges1 or may m or less disappe>1 two d>k spots or blot*es be+ br\ght prom95tly into view4 ,if r+s are /ill se5 x w be notic$ t !y h exp&$ 9 ! quadrants occupi$ by ! d>k spots1 & h contract$ 9 ! rema9+ quadrants4 ,?is movem5t ( ! r+s may make x possible to det]m9e ! optical "* ( a section1 :i* is s oblique to ! optic axis t ! d>k spots are n se5 aft] ! introduction ( ! mica plate4 ,illu/ration3 ,,fig4 #bf4 ,illu/ration3 ,,fig4 #bg4 ,if ! optical "* is positive ! l9e jo9+ ^! d>k spots is p]p5dicul> to ! direction c ( ! mica plate1 see ,fig4 #bf4 ,if negative ! l9e jo9+ ! d>k spots co9cides ) ! direction c ( ! mica plate1 see ,fig4 #bg4 ,! 77 & 77 "* is easily det]m9$ by rememb]+ t ! l9e1 jo9+ ! d>k spots1 makes ! & sign respectively ) ! direction c ( ! mica plate4 ,! direction c ( ! mica plate 7repres5t$ 9 ! figures by an arr[7 is ( c\rse n se51 b its position mu/ be borne 9 m9d :5 mak+ ?is te/4 ,?is te/ c be made ) ei!r mono*romatic or :ite light4 ,if ! mica plate does n give satisfactory results1 :i* w be ! case :5 ! d\ble refraction ( ! cry/al to be te/$ is v weak or :5 ! section is v ?91 use a sel5ite plate1 cut ! prop] ?ickness to give ! r$ color ( ! fir/ ord]4 ,?is plate mu/ be introduc$ ) its vibration direction a 7previ\sly det]m9$7 mak+ an angle ( #de ) ! planes ( vibration ( ! nicols4 ,in/ead ( ! d>k spots be+ se5 !re w appe> two blue & two r$ quadrants4 ,! diagonally opposite quadrants be+ ( ! same color4 ,9 det]m9+ ! 77 & 77 "* consid] ! blue quadrants z ! equival5t ( ! d>k spots 9 ! prec$+ case4 ,?is te/ mu/ be made ) :ite light4#gb ,biaxial ,int]f]5ce ,figures4 ,illu/ration3 ,,fig4 #bh4 ,illu/ration3 ,,fig4 #bi4 7a7 ,sections p]p5dicul> to an optic axis exhibit ! int]f]5ce figures %[n 9 ,figs4 #bh & #bi1 ! curves be+ ne>ly circul> & a /raight black b> bisect+ ^! curves1 :5ev] ! trace ( ! plane ( ! optic axes co9cides ) ! vibration direction ( ei!r nicol4 ,z ! /age1 c>ry+ ! section1 is rotat$ ! b> *anges into "o arm ( a hyp]bola & back aga9 into a b>4 ,?is arm or b> w rotate 9 ! opposite direction to ! motion ( ! /age4 ,z previ\sly /at$ sections ( biaxial cry/als1 p]p5dicul> to an optic axis1 d n rema9 d>k dur+ rotation ( ! /age betwe5 cross$ nicols 9 p>allel light4 ,on ! contr>y ^! sections rema9 uni=mly illum9at$4#gc 7b7 ,sections p]p5dicul> to ! acute bisectrix 7see p4 #e71 exhibit int]f]5ce figures l ^? %[n 9 ,figs4 #cj & #ca4 ,illu/ration3 ,,fig4 #cj4 ,illu/ration3 ,,fig4 #ca4 ,fig4 #cj %[s ! appe>ance ( ! int]f]5ce figure :5 ! plane ( ! optic axes is p>allel to ! plane ( vibration ( ei!r nicol1 & ,fig4 #ca %[s ! appe>ance :5 ?is plane is incl9$ #de to ! planes ( vibration ( ! nicols4 ,z ! /age1 c>ry+ ! section1 is rotat$ ! d>k cross seems to dissolve into two bran*es ( a hyp]bola1 :i* aga9 unite to =m a cross4 ,9 sections p]p5dicul> to a bisectrix1 ) a l>ge axial angle1 ! figure w appe>1 dur+ a rotation ( #ij 79 ! direction ( ! h&s ( a wat*71 z 9 ,fig4 #cb1 top r[4 ,:5 ! section is some:at oblique to an 8optic axis10 ! figure appe>s z 9 middle r[2 & :5 /ill m oblique1 z 9 bottom r[4 ,! black c5tres#gd ( ! small ellipses & ! black hyp]bolic curves m>k ! po9ts ( em]g5ce ( ! optic axes1 & !re=e indicate approximately ! size ( ! axial angle1 #b;,e4 ,sections 9 o!r positions1 relative to ! optic axes1 give int]f]5ce figures less def9ite 9 appe>ance ?an ^? j describ$2 & ! same conditions affect ! appe>ance ( all figures z 9 ! case ( uniaxial cry/als4 ,v ?9 sections1 ( weak d\ble refraction1 may only %[ indi/9ct d>k crosses or hyp]bolic curves1 )\t any ellipses4 ,! section p]p5dicul> to ! acute bisectrix1 :i* gives ! mo/ *>act]i/ic int]f]5ce figure1 _c g5]ally be recogniz$ except by an exam9ation 9 conv]g5t light4 ,x is nev]1 h[ev]1 ! section giv+ ! maximum int]f]5ce color4 ,! int]f]5ce colors 9 diff]5t sections1 normal to ! optical elem5ts1 grade d[nw>d 9 ! foll[+ ord]3 7#a7 optic normal1 7#b7 obtuse bisectrix1 7#c7 acute bisectrix1 7#d7 optic axis4 ,sometimes cleavage may furni% a clue z to ! be/ section to te/ z 9 ,topaz & ,mica1 :]e ! acute bisectrix is normal to ! cleavage4 ,illu/ration3 ,,fig4 #cb4--;,biaxial ,int]f]5ce ,figures 7f ,re9is*74 ,top r[3 ,almo/ p]p5dicul> to bisectrix1 l>ge axial angle4 ,middle r[3 ,some:at oblique to an 8optic axis40 ,bottom r[3 ,m oblique to an 8optic axis40 ,x mu/ be rememb]$ t ?is unc]ta9ty1 9 ! *oice ( sections = te/+1 does n exi/ 9 uniaxial cry/als2 :]e ! be/ sections are indicat$ by ! fact t !y rema9 d>k or ne>ly s dur+ complete rotation betwe5 cross$ nicols4 ,! uniaxial or biaxial "* ( a m9]al section1 :i* only %[s an indi/9ct b>1 may be det]m9$ z foll[s3 ,a b> 7"o arm ( ! cross7 ( a uniaxial int]f]5ce figure moves 9 ! same direction z ! rotat+ /age1 & always rema9s /raight1 :ile ! biaxial b> rotates 9 ! opposite direction to ! /age & becomes curv$4 ,optical ,"*1 ,positive or ,negative4 ,:5 ! axial angle is v small1 s t ! int]f]5ce figure approa*es t ( a uniaxial cry/al1 ! me?ods us$ = te/+ uniaxial figures are employ$4 ,:51 h[ev]1 ! axial angle is l>ge1 ! foll[+ me?od c be us$3 ,aft] hav+ obta9$ an int]f]5ce figure1 f a section z ne>ly at "r angles to ! acute bisectrix#ge z possible1 ! /age is rotat$ until ! plane ( ! optic axes 7! trace ( :i* on ! plane ( ! section is ! l9e jo9+ ! po9ts ( em]g5ce ( ! two optic axes7 makes an angle ( #de ) ! planes ( vibration ( ! cross$ nicols or ! cross-wires 9 ! eye-piece4 ,a qu>tz w$ge#gf is n[ pu%$ 9 betwe5 ! m9]al section & ! analyz]1#gg s t its axis c 7previ\sly det]m9$ & m>k$ on ! w$ge7 is ei!r at "r angles or p>allel to ! plane ( ! optic axes ( ! m9]al section4 ,! optical "* ( ! m9]al is positive :5 ! ellipses1 surr\nd+ ! po9ts ( em]g5ce ( ! two optic axes on ! convex sides ( ! hyp]bola1 appe> to exp& or op5 out t[>ds ! c5tre :5 ! qu>tz w$ge is pu%$ 9 ) its axis p>allel to ! plane ( ! optic axes4 ,! optical "* is negative :5 ! ellipses appe> to exp& or op5 out :5 ! w$ge is pu%$ 9 ) its axis at "r angles to ! plane ( ! optic axes4 ,z ! ellipses exp& !y move f ! po9ts ( em]g5ce ( ! optic axes t[>ds ! c5tre ( ! int]f]5ce figure1 & f9ally op5 into lemniscates :i* move outw>d f ! plane ( ! optic axes4 ,ev5 :5 ! section is v ?9 & ! d\ble refraction v weak1 only ! black hyp]bolas )\t ellipses be+ se51 ! te/ c be made2 & color$ ellipses w appe>1 aft] ! pu%+ 9 ( ! qu>tz w$ge1 :i* w act 9 ! same way z ! ellipses ( ! int]f]5ce figure4 ,9 a section at "r angles to ! obtuse bisectric ^! results are all rev]s$4 ,:5 ! section is p]p5dicul> to "o optic axis1 rotate ! section until ! plane ( its optic axes is #de to ! planes ( vibration ( ! nicols4 ,! int]f]5ce figure w n[ h ! appe>ance z %[n 9 ,fig4 #bi1 ! hyp]bola be+ convex t[>ds ! acute bisectrix4 ,ins]t ! undulation mica plate1 s t its direction c is p>allel to ! plane ( ! optic axes4 ,if ! optical "* is positive ! hyp]bola w move t[>ds ! acute bisectrix & if negative away f x4 ,:5 ! gypsum plate is us$ ! blue color w appe> on ! convex side = 77 & on ! concave side = 77 m9]als4 ,det]m9ation ( ! ,axial ,angle4#gh ,?is c be approximately det]m9$ ) a petrographical microscope1 if equipp$ ) a micromet] eye-piece4 ,h ! axial plane ( ! cry/al section 9 ! diagonal position1 ,fig4 #ca2 & measure ! di/ance d f ! c5tre to ei!r hyp]bola ) a micromet] 7or av]age ! di/ance to bo?74 ,!n s9 ,e d_/,c1 9 :i* ,c is a con/ant = ! same comb9ation ( l5ses & is obta9$ by us+ a cry/al section 7mica cleavage7 ( kn[n axial angle4 ,= example1 9 a mica ) #b;,e #ia #ej & d #da4e divisions on ! micromet] scale1 ,c d_/s9 ,e #eg4gh = t special comb9ation ( l5ses4 ,! true axial angle c be obta9$ f ! equation s9 ,v d_/,c4 ,optical ,di/9ctions betwe5 ,or?orhombic1 ,monocl9ic1 & ,tricl9ic ,cry/al ,sections 7p]p5dicul> to acute & obtuse bisectrices74 ,! int]f]5ce figures are always symmetrical 9 %ape & di/ribution ( color to ! planes & axes ( symmetry ( ! cry/al sy/em2 h5ce are mo/ symmetrical 9 ! or?orhombic1 less s 9 ! monocl9ic & /ill less s 9 ! tricl9ic sy/em4 ,or?orhombic cry/als %[ ! figures always 9 two ( ! p9acoids & 9 :ite light ! color di/ribution w be symmetrical to ! trace ( ! axial plane & ! l9e ?r\gh ! c5tre at "r angles to ?is trace & also to ! c5tral po9t4 ,monocl9ic cry/als %[ ! figures 9 ! cl9o p9acoid or 9 sections at "r angles to ?is4 ,9 :ite light ! color di/ribution is nev] symmetrical to two l9es1 b is symmetrical ei!r to ! trace ( ! axial plane 7incl9$ disp]sion#gi71 or to ! l9e ?r\gh ! c5tre at "r angles to ?is trace 7horizontal disp]sion71 or to ! c5tral po9t 7cross$ disp]sion74 ,tricl9ic cry/als %[ 9 :ite light figures ) di/ribution ( color unsymmetrical to any l9e or po9t4 ,9 :ite light ! 8color fr+es0 ( ! hyp]bola are due to ! 8disp]sion0#gi ( ! optic axes & bisectrices4 ,t is1 = ea* color 7= light ( ea* wave-l5g?7 !re is a p>ticul> int]f]5ce figure2 ! ov]lapp+ ( ^! sup]pos$ figures produc+ ! color fr+es4 ,:5 ! axial angle is l>g] = r$ light ?an = violet1 ! disp]sion is said to be & ! int]f]5ce figure1 9 ! position ( ,fig4 #ca1 w %[ ! hyp]bolic curves fr+$ ) r$ t[>ds ! c5tre 7inside74 ,9 g5]al ! color ) ! l>g] axial angle is ne>] ! c5tre ( ! field4 ,?is is due to ! ext+ui%+ ( light ( ea* color at ! axial po9ts1 ! result+ colors at ^! po9ts be+ produc$ by :ite light m9us ! absorb$ color4 ,:5 ! disp]sion is ! rev]se di/ribution ( color fr+es w take place4 ,by measur+ ! axial angle 9 r$ & blue light1 ?is disp]sion ( ! optic axes c also be obta9$4 ,,resum ,,( ,,! ,,uses ,,( ,,p>allel ,,& ,,conv]g5t ,,pol>iz$ ,,light4 ,p>allel light is us$ to detect pleo*roism1 to di/+ui% betwe5 isotropic & anisotropic sub/ances1 to /udy int]f]5ce colors1 to det]m9e ! /r5g? ( ! d\ble refraction1 to locate directions ( vibration1 to measure ext9ction angles1 to f9d ! directions ( vibration ( ! fa/] & sl[] rays1 to det]m9e ! relative value ( ! indices ( refraction ( ! two rays1 & to inve/igate ! cry/al /ructure 9 g5]al4 ,conv]g5t light is us$ to di/+ui% betwe5 uniaxial & biaxial cry/als1 to det]m9e :e!r a section t appe>s to be isotropic is really s or only p]p5dicul> to an optic axis & to det]m9e ! optical "*1 grade ( symmetry 7sy/em71 axial angle & disp]sion4 ,,*apt] ,,iv4 ,,! ,,microscopic ,,& ,,optical ,,*>act]s ,,( ,,m9]als4 ,,opal4 ,,isotropic4 ,,amorph\s4 ,,composition3 ,si,o#b4n,h#b,o1 g5]ally soluble 9 cau/ic alkalies4 ,usual ,appe>ance 9 ,sections3 ,colorless pat*es1 incru/ations or ve9s1 also at times ) sphrulitic /ructure 7hyalite71 %[+ int]f]5ce cross1 ( negative "*1 betwe5 cross$ nicols4 ,(t5 %[s anomal\s d\ble refraction due to /ra9s4 ,! refractive index is v l[ 7#a4df7 s t ! surface ( ! opal appe>s r\gh4 ,,rem>ks3 ,f\nd z a second>y m9]al 9 _m acid volcanic rocks1 rhyolite1 tra*yte1 &esite1 etc41 & also 9 basic basalts4 ,h41 #e4e to #f4e4 ,sp4 gr41 #b4b4 ,,limonite4 ,,amorph\s4 ,,composition3 ,fe#b7,,oh7#f1 ,fe#b,o#c1 frequ5tly q impure4 ,usual ,appe>ance 9 ,sections3 ,br[ni% & opaque1 9 v ?9 sections may be transluc5t4 ,,rem>ks3 ,limonite is ess5tially a decomposition product1 (t5 =m+ pseudomorphs aft] f]rug9\s silicates or halos ab\t ! iron ores4 ,,pyrite1 ,pyrites4 ,,isometric4 ,,composition3 ,fe,s#b4 ,usual ,appe>ance 9 ,sections3 ,cubes1 pyritoh$rons1 comb9ations ( ^! =ms2 or 9 irregul> gra9s4 ,outl9e ( cross-sections g5]ally squ>e4 ,opaque1 & by reflect$ light1 bright yell[1 ) /rong metallic lu/re4 ,alt]s v easily to ! oxides ( iron 7ru/74 ,,rem>ks3 ,may be pres5t 9 all k9ds ( rocks1 igne\s1 metamorphic & s$im5t>y4 ,n noticeably act$ on by hydro*loric acid4 ,h41 #f to #f4e4 ,sp4 gr41 #d4i to #e4b4 ,,pyrrhotite1 ,magnetic ,pyrites4 ,,composition3 ,fe,s4 ,di/+ui%$ f pyrite by be+ practically always 9 irregul> masses & n 9 cry/als1 & by bronze yell[ color ) reflect$ light4 ,f\nd 9 basic eruptive rocks1 m r>ely 9 s*i/s4 ,,magnetite1 ,magnetic ,iron ,ore4 ,,isometric4 ,,composition3 ,fe#c,o#d1 (t5 conta9s ,ti4 ,usual ,appe>ance 9 ,sections3 ,gra9s & cry/als 7g5]ally octah$ra71 ,fig4 #cc ,b4 ,skeleton cry/als frequ5t 9 highly f]rug9\s eruptive rocks4 ,tw9n+4--,common1 accord+ to ,sp9el law4 ,illu/ration3 ,,fig4 #cc4--;,a1 ,zircon cry/als 7isolat$ f granite7 9 balsam1 %[+ high relief4 ,b1 ,magnetite cry/als4 ,c1 ,ilm5ite1 %[+ p>tial decomposition to leucox5e along cry/allographic directions4 ,opaque1 & by reflect$ light1 blui%-black1 ) /rong metallic lu/re4 ,di/+ui%$ f3 ,,hematite1 ,,*romite1 ,,ilm5ite & ,,graphite1 by be+ easily sep>at$ f p[d]$ rock by weak magnet4 ,,rem>ks3 ,v widely di/ribut$ 9 eruptive rocks & cry/all9e s*i/s4 ,9 ! eruptive rocks magnetite belongs to ! olde/ secretions f ! magma1 imm$iately foll[$ by *rysolite1 biotite1 hornbl5de1 augite1 etc42 h5ce (t5 appe>s z inclusions 9 ^! & o!r m9]als4 ,magnetite gra9s may =m ) o!r sub/ances pseudomorphs aft] hornbl5de1 biotite1 hyp]/h5e1 etc4 ,su* pseudomorphs appe> to be caus$ by 8resorption40 ,magnetite is /rongly magnetic & soluble 9 hydro*loric acid4 ,h41 #e4e to #f4e4 ,sp4 gr41 #d4i to #e4b4 ,,*romite4 ,,isometric4 ,,composition3 ,fe,cr#b,o#d4 ,usual ,appe>ance 9 ,sections3 ,octah$ral cry/als1 gra9s & 9 ! oliv9e rocks sometimes 9 d5se aggregates4 ,may be surr\nd$ by gre51 pleo*roic halo ( *rome o*re4 ,opaque1 & by reflect$ light1 br[ni%-black to black1 ) g5]al abs5ce ( metallic lu/re4 ,usually transluc5t & br[ni% on ! edges 7by transmitt$ light71 ) a v r\gh surface due to high index ( refraction 7n #b4a74 ,di/+ui%$ f3 7a7 ,,magnetite by br[ni%-black to black color & g5]al abs5ce ( metallic lu/re 7by reflect$ light7 & by gra9s be+ usually transluc5t & br[ni% on ! edges 7by transmitt$ light74 7b7 ,,sp9el 7,picotite71 see "u ,sp9el4 ,,rem>ks3 ,common 9 cry/all9e rocks1 ri* 9 magnesia1 & 9 s]p5t9e4 ,*romite is n act$ on by acids1 is non-magnetic & gives *romium bead te/4 ,h41 #e4e4 ,sp4 gr41 #d4c to #e4f4 ,,sp9el4 ,,isotropic4 ,,isometric4 ,,composition3 ,mg7,al,o#b7b4 ,pleona/e 7,fe1 ,mg sp9el71 ,picotite 7,cr sp9el74 ,usual ,appe>ance 9 ,sections3 ,octah$ral cry/als & tw9s 7aft] sp9el law71 less (t5 9 gra9s4 ,fracture cracks4 ,always optically normal & nev] decompos$ 9 rocks4 ,usually colorless or d>k gre5 7pleona/e7 to br[n 7picotite74 ,! refractive index is high 7n #a4gb1 sp9el prop]1 to #b4jj1 *rome sp9el71 h5ce ! relief is m>k$ & ! surface r\gh4 ,di/+ui%$ f3 7a7 ,,g>net :5 colorless by octah$ral %ape ( cry/als 7g>net =ms be+ #aaj & #baa71 :5 br[n 7picotite7 f melanite g>net by common zonal coloration ( ! latt]1 b may require *emical te/s4 ,fur!rmore sp9el may h gre5 color & is nev] decompos$4 7b7 ,,p]ovskite by ! l[] index ( refraction & ! abs5ce ( reaction = ,ti4 7c7 ,,*romite *emically or by d5sity or h>dness4 ,,rem>ks3 ,f\nd 9 gneiss1 granulite1 lh]zolite & 9 regions ( contact metamorphism & second>y b$d+ =mations 7picotite71 oliv9e-basalt & s]p5t9e4 ,sp9els are insoluble 9 hydro*loric acid4 ,h41 #h4 ,sp4 gr41 #c4e to #d4a4 ,,g>net4 ,,isotropic4 ,,isometric4 ,,composition3 ,r#c,r#b7,si,o#d7c4 ,r is ,ca1 ,mg1 ,fe or ,mn2 ,r is ,al1 ,fe1 or ,cr1 r>ely ,ti4 ,usual ,appe>ance 9 ,sections3 ,irregul> gra9s1 ,fig4 #ac1 or simple cry/als1 %[+ =ms 7#aaj7 & 7#baa71 alone or 9 comb9ation1 ,fig4 #ad b4 ,zonal /ructure n infrequ5t1 especially 9 ! titanium v>ieties1 ,fig4 #cd4 ,color4--,colorless1 or ne>ly s1 to yell[i%1 r$di% or br[ni%4 ,index ( ,refraction4--n #a4gej-a4hef1 h5ce relief high & surface v r\gh4 ,fracture4--,irregul> cracks occur1 b no cleavage notic$4 ,cross$ ,nicols3 ,z g>nets are isotropic1 sections rema9 d>k dur+ complete rotation4 ,optical anomalies may h[ev] occur1 b are g5]ally conf9$ to1 titanium free1 lime g>nets & manganese g>nets4 ,! effect be+ to divide ! cry/al symmetrically into diff]5t areas1 8dodecah$ral /ructure40 ,illu/ration3 ,,fig4 #cd4--;,g>net1 ) zonal /ructure1 9 gneiss4 7,f ,coh547 ,alt]ation3 ,g>nets are usually fre%1 b may be f\nd alt]$ to *lorite or hornbl5de4 ,di/+ui%$ f3 ,,sp9el & ,,p]ovskite4--,see "u ! latt]4 ,,rem>ks3 ,f\nd pr9cipally 9 granulites1 metamorphic rocks1 contact rocks1 cry/all9e s*i/s1 etc4 ,c]ta9 v>ieties may be f\nd 9 eruptive rocks or oliv9e rocks4 ,may =m pegmatitic bord]s ) pyrox5e1 sp9el1 etc4 ,g>nets are practically insoluble 9 hydro*loric acid4 ,h41 #f4e to #g4e4 ,sp4 gr41 #c4d to #d4c4 ,! insolubility 9 acids & ! high sp4 gr4 help 9 sep>at+ g>net f a p[d]$ rock4 ,,leucite4 ,,isotropic4 ,,isometric4#hj ,,composition3 ,k,al7,si,o#c7b4 ,usual ,appe>ance 9 ,sections3 ,cry/als or gra9s1 :i* v>y greatly 9 size4 ,cross-sections (t5 ne>ly r\nd4 ,:5 v small & free f inclusions may be easily ov]look$4 ,sometimes ! gra9s are surr\nd$ by tang5tially arrang$ ne$les ( diff]5t m9]als4 ,illu/ration3 ,,fig4 #ce4--,leucite1 ) radial & tang5tial inclusions1 ,vesuvius ,lava4 7,f ,coh547 ,color4--,colorless4 ,index ( ,refraction4--n #a4eji1 h5ce no relief & g5]ally smoo? surface4 ,fracture4--,may be notic$1 b no cleavage obs]v$4 ,inclusions4--,common1 radially or zonally arrang$1 consi/+ ( m9]als or glass1 ,fig4 #ce4 ,cross$ ,nicols3 ,! small] cry/als appe> isotropic2 ! l>g] cry/als %[ *>act]i/ic int]sect+ sy/ems ( tw9 lamell1 ,fig4 #cf4 ,illu/ration3 ,,fig4 #cf4--,leucite1 %[+ complicat$1 int]p5etration tw9n+ betwe5 cross$ nicols4 ,d\ble ,refraction4--,v weak 7 #j4jja74 ,9 ?9 sections x may be necess>y to use a s5sitive color plate to prove d\ble refraction4 ,int]f]5ce ,colors4--,v l[ #a/ ord]1 d>k gray1 etc4 ,alt]ation3 ,q frequ5t to fibr\s or granul> zeolites4 ,di/+ui%$ f3 ,,analcite--see "u analcite4 ,,rem>ks3 ,almo/ entirely conf9$ to y\ng] eruptive rocks1 phonolite1 tephrite & o!r leucite rocks & _! tuffs4 ,(t5 f\nd ) plagioclase1 nephelite1 augite1 etc4 ,x is m or less attack$ by hot hydro*loric acid4 ,h41 #e4e to #f4 ,sp4 gr41 #b4d to #b4e4 ,! isolation ( leucite f rock p[d] c be bett] accompli%$ by specific gravity ?an by *emical me?ods4 ,,analcite4 ,,isotropic4 ,,isometric4 ,,composition3 ,na,al,si#b,o#f ,h#b,o4 ,usual ,appe>ance 9 ,sections3 ,second>y colorless gra9s1 ) no v *>act]i/ic micro/ructure or prop]ties4 ,cleavage p>allel to cube 7#ajj7 usually se54 ,index ( refraction l[ 7n #a4dhh71 h5ce r r\gh surface4 ,betwe5 cross$ nicols may %[ optical anomalies1 b n s m>k$ z 9 g>net4 ,di/+ui%$ f3 ,,leucite1 ,,sodalite & ,,nephelite4 ,^! m9]als are mo/ easily confus$ ) analcite & rec\rse mu/ be _h to *emical te/s1 detection ( optical anomalies1 gelat9ization te/ or turbidity by heat+4 ,,rem>ks3 ,occurs z a second>y product 7commonly f nephelite or leucite7 9 alkali-ri* eruptive rocks4 ,consid]$ also z a prim>y m9]al 9 igne\s rocks4#ha ,gelat9izes ) hydro*loric acid1 & becomes turbid by heat+4 ,h41 #e4e4 ,sp4 gr41 #b4be4 ,,sodalite ,,gr\p4 ,sodalite1 ,haynite 7,hayne7 & ,noselite 7,nosean74 ,,isotropic4 ,,isometric4 ,,composition3 ,sodalite1 #c,na,al,si,o#d ,na,cl4 ,haynite1 #b7,na#b;,ca7,al#b7,si,o#d7b 7,na#b;,ca7,,s#d4 ,noselite1 #b,na#b;,al#b,si#b,o#h ,na#b,,s#d4 ,usual ,appe>ance 9 ,sections3 ,dodecah$ral r\nd$ cry/als or 7,s7 irregul> gra9s4 ,colorless1 yell[i%1 br[ni%1 gre5i% to deep blue4 ,refractive index l[ n #a4dhc7,s7 to #a4ejc7;,h71 h5ce ! surface appe>s r r\gh 9 sodalite & slightly r\gh 9 haynite4 ,inclusions1 abundant & *>act]i/ic1 (t5 rod-l & arrang$ regul>ly1 mak+ section transluc5t & especially d>k at bord]1 ,fig4 #cg4 ,dodecah$ral cleavage sometimes se54 ,optical anomalies may occur4 ,alt]ation3 ,takes place easily to aggregates ( natrolite1 o!r zeolites1 mica1 etc4 ,di/+ui%$ f3 7a7 ,,"o ,,ano!r only by *emical te/s4 ,gelat9ization te/ ) hydro*loric acid w %[ 9 addition to jelly1 salt cry/als = 7,s71 abundant gypsum cry/als 7,ca,s,o#b #b;,h#b,o7 = 7,h7 & few if any gypsum cry/als 7abs5ce ( ,ca7 = 7,n74 7,h7 & 7,n7 turn blue :5 heat$1 b te/ w n "w if m9]als are decompos$4 ,:5 treat$ ) hydro*loric acid & nitrate ( silv] ! black sulphide ( silv] w %[ on 7,h7 & 7,n71 b ! :ite *loride on 7,s74 7b7 ,,nephelite 7,elolite7 by be+ isotropic4 7c7 ,,analcite by no turbidity :5 heat$4 ,,rem>ks3 ,^! m9]als are f\nd 9 ! basic1 soda-ri* rocks4 7,s7 9 elolite-sy5ite also 9 tra*yte & phonolite1 7,h7 & 7,n7 common 9 phonolite & leucite-porphyry4 ,h41 #e4e to #f4 ,sp4 gr41 #b4c4 ,illu/ration3 ,,fig4 #cg4--;,haynite1 %[+ d>k c5tre & bord]1 9 nepel9ite4 7,f ,coh547 ,,p]ovskite1 ,p](skite4 ,,isotropic4 ,,isometric4 ,,composition3 ,ca,ti,o#c4 ,usual ,appe>ance 9 ,sections3 ,microscopic1 octah$ral cry/als or l>g] gra9s1 pale br[ni% 9 color & n v transp>5t1 d>k] color$ 9 ! l>g] gra9s4 ,9 reflect$ light gra9s appe> yell[i% ) adamant9e lu/re4 ,refractive index v high 7n #b4ch71 h5ce relief v /rong4 ,betwe5 cross$ nicols1 ! little cry/als g5]ally appe> optically normal & rema9 d>k2 b ! l>g] cry/als may %[ a complicat$ p5etration tw9n+4 ,di/+ui%$ f3 ,,g>net 7melanite7 & ,,sp9el 7picotite7 by mu* high] refractive index & reaction = titanium & by zonal coloration ( melanite4 ,:5 opaque x might be mi/ak5 = ! iron ores1 b has no metallic lu/re4 ,,rem>ks3 ,f\nd 9 ! y\ng] basic eruptive rocks1 especially melilite-basalt4 ,commonly associat$ ) ! iron ores nephelite1 augite & *rysolite4 ,insoluble 9 hydro*loric acid4 ,h41 #e4e4 ,sp4 gr41 #d4a4 ,,rutile4 ,,anisotropic4 ,,uniaxial4 ,,tetragonal4 ,,composition3 ,ti,o#b4 c ,,elongation 4 ,usual ,appe>ance 9 ,sections3 ,%>p1 elongat$1 prismatic cry/als :5 microscopic1 b granul> :5 ! individuals are l>ge4 ,gra9s may be almo/ opaque1 ) adamant9e lu/re by reflect$ light4 ,knee- or he>t-%ap$ tw9s1 ,figs4 #ch & #ci1 common 9 ! small] cry/als1 ! l>g] individuals may also %[ g5iculat$ tw9n+4 ,small cry/als sometimes =m net-%ap$ gr\ps 7sag5ite71 by cross+ "o ano!r at angles ( #fj4 ,pleo*roic halos may surr\nd cry/als4 ,color1 yell[i% to r$di%-br[n4 ,index ( refraction v high 7n #b4gab1 #b4faf1 #b4ijc71 h5ce relief m>k$ & surface v r\gh4 ,prismatic cleavage pres5t 9 l>g] individuals1 n obs]v$ 9 microscopic cry/als4 ,pleo*roism & /rong absorption may be notic$1 especially 9 ! l>g] gra9s1 b may fail entirely4 ,cross$ ,nicols3 ,d\ble refraction v /rong 7 #j4bhg74 ,int]f]5ce colors#hb v high ord]1 only se5 9 ! microlitic cry/als :i* d n appe> d>k due to total reflection2 9 o!r cases may n %[ at all4 ,ext9ction p>allel to prisms4 ,9 conv]g5t light optical "* 774 ,alt]ation3 ,may take place to a :ite or yell[i%1 fibr\s or granul> sub/ance1 /rongly refract+1 & simil> to ! alt]ation product ( ilm5ite4 ,may be surr\nd$ by gra9s ( titanite4 ,di/+ui%$ f3 ,! ,,opaque ,,ores by adamant9e lu/re ) reflect$ light2 ,,zircon & ,,cassit]ite 9 conc5trates by *emical te/s4 ,may n be possible to di/+ui% f cassit]ite 9 sections4 ,,rem>ks3 ,f\nd 9 ! metamorphic s*i/s1 amphibolites1 slates1 contact & fragm5t>y rocks1 etc42 also z inclusions 9 qu>tz & mica4 ,especially common z a second>y product ( titanif]\s hornbl5de & biotite4 ,! 8sag5ite0 webs ( ! decompos$ micas are probably second>y4 ,rutile is insoluble 9 hydro*loric acid4 ,h41 #f to #f4e4 ,sp4 gr41 #d4b4 ,x is easily sep>at$ f rock p[d] by its insolubility 9 acid & its high sp4 gr4 ,illu/ration3 ,rutile tw9s4 ,,fig4 #ch4--,tw9 plane 7#aja74 ,,fig4 #ci4--,tw9 plane 7#cja74 ,,zircon4 ,,anisotropic4 ,,uniaxial4 ,,tetragonal4 ,,composition3 ,zr,si,o#d4 c 4 ,,elongation c4 ,usual ,appe>ance 9 ,sections3 ,small1 %ort prismatic cry/als1 ,fig4 #cc;,a1 & gra9s4 ,%ell-l 7zonal7 /ructure may be notic$4 ,:5 enclos$ 9 black-mica1 hornbl5de1 cordi]ite1 etc41 (t5 surr\nd$ by *>act]i/ic pleo*roic halos4#hc ,color4--,colorless1 r>ely pale br[ni%4 ,index ( ,refraction4--n #a4ie1 7 #a4ica1 #a4iic7 h5ce relief v high & surface r\gh4 ,pol>iz$ ,light3 ,pleo*roism4--,n usually noticeable4 ,cross$ ,nicols3 ,d\ble ,refraction4--,v /rong 7 #j4jfb74 ,int]f]5ce ,colors4--,v high 7#d?7 ord]1 m9ute cry/als %[ brilliant colors4 ,ext9ction4--,z zircon is uniaxial1 basal sections rema9 d>k dur+ rotation ( /age4 ,9 all o!r sections ext9ction is p>allel to 4 ,conv]g5t ,light3 ,basal sections1 :i* are l>ge en\gh to give int]f]5ce figures1 %[ sev]al r+s 9 addition to d>k cross4 ,optical "* 774 ,alt]ation3 ,v r>ely takes place4 ,di/+ui%$ f3 7a7 ,,apatite4--,by mu* high] relief & /rong] d\ble refraction4 7b7 ,,titanite4--,by uniaxial "*4 7c7 ,,rutile4--,see "u ! latt]4 ,easily confus$ ) x5otime1 :i*1 h[ev]1 has high] int]f]5ce colors & m di/9ct pleo*roism2 b *emical te/s may be necess>y4 ,,rem>ks3 ,f\nd widely di/ribut$ b n 9 quantity 9 eruptive & metamorphic rocks4 ,occurs 9 granite1 sy5ite1 diorite1 gabbro1 gneiss1 etc4 ,x is "o ( ! olde/ con/itu5ts ( ! rocks 9 :i* x occurs1 & may (t5 be f\nd z inclusions 9 ! f]ro-magnesium m9]als4 ,zircon is insoluble 9 hydro*loric acid4 ,h41 #g4e4 ,sp4 gr41 #d4e to #d4g4 ,x c easily be sep>at$ f rock p[d] on acc\nt ( its high sp4 gr41 insolubility 9 acid & non-magnetic prop]ties4 ,! cry/als c !n be exam9$ sep>ately1 or *emical te/s made to prove ! pres5ce ( ,zr4 ,,scapolite ,,gr\p1 ,w]n]ite1 etc4 ,,anisotropic4 ,,uniaxial4 ,,tetragonal4 ,,composition3 ,silicates ( ,ca1 ,al a4 ,,elongation a4 & ,na4 ,usual ,appe>ance 9 ,sections3 ,colorless gra9s1 la?-l individuals or prisms 7dipyre1 9 contact metamorphic lime/one74 ,index ( refraction 7n #a4eea to #a4ehd21 #a4edb to #a4eeh1 #a4eee to #a4eig7 ab\t ! same z qu>tz1 h5ce usually no relief & surface smoo?4 ,cleavage di/9ct p>allel to squ>e prism4 ,inclusions 7c>bonace\s7 may be abundant 9 contact rocks4 ,cross$ ,nicols3 ,d\ble refraction usually /rong1 b v>ies 7 #j4jac to #j4jci71 increases ) ! ,ca p]c5tage4 ,int]f]5ce colors upp] #a/ or #b;d ord]1 m brilliant ?an ^? ( mo/ ( ! colorless m9]als4 ,basal sections 7%[+ cleavages int]sect+ at #ij7 isotropic4 ,ext9ction p>allel 9 longitud9al sections4 ,9 conv]g5t light basal sections %[ di/9ct uniaxial int]f]5ce figure2 optical "* 774 ,alt]ation3 ,takes place easily to a fibr\s sub/ance or to kaol91 muscovite1 etc4 ,di/+ui%$ f3 7a7 ,,feldsp>s 7n %[+ tw9n+7 & ,,iolite 7,cordi]ite7 by uniaxial "*1 cleavage & high] ord] int]f]5ce colors4 7b7 ,,qu>tz by cleavage1 high] ord] int]f]5ce colors & optical "*2 qu>tz is 77 7c7 ,,apatite 79 gra9s7 by l[] index ( refraction1 cleavage & high] ord] int]f]5ce colors4 ,,rem>ks3 ,f\nd especially 9 metamorphos$ diabases & gabbros 7,norwegian72 also 9 gneisses1 cry/all9e s*i/s1 metamorphos$ lime/ones1 etc4 ,dipyre occurs 9 contact zones ( lime/ones & s*i/s1 :]e x might be confus$ ) &alusite1 b cross-sections %[ uniaxial "*4 ,! m9]als ( ?is gr\p are m or less soluble 9 hydro*loric acid4 ,:5 ! scapolite conta9s ,cl1 ! foll[+ te/ c be made on fre% mat]ial4 ,treat ) a solution ( silv] nitrate 9 hydr(luoric acid & ! jelly w be impregnat$ ) *loride ( silv] :i* w turn br[n4 ,h41 #e4e4 ,sp4 gr41 #b4fh4 ,,vesuvianite1 ,idocrase4 ,,anisotropic4 ,,uniaxial4 ,,tetragonal4 ,,composition3 a4 ,,elongation a4 ,ca#f;,al#c7,,oh4,f77,si,o#d7f4 ,usual ,appe>ance 9 ,sections3 ,gra9s or prismatic cry/als4 ,almo/ colorless to r$di% 7:5 conta9+ ,mn74 ,index ( refraction high 7n #a4gae1 #a4gja to #a4gbf1 #a4gje to #a4gcb71 h5ce relief m>k$ & surface r\gh4 ,cleavage imp]fect1 p>allel to prism4 ,pleo*roism g5]ally v fa9t4 ,cross$ ,nicols3 ,d\ble refraction v weak 7 #j4jja to #j4jjf71 may v>y 9 diff]5t portions ( ! same cry/al 7optical anomalies due to ! m9]al be+ at times a mixture ( isomorph\s individuals74 ,int]f]5ce colors v l[ #a/ ord]1 d>k gray1 etc41 may (t5 appe> zonal4 ,basal sections isotropic :5 normal1 b may %[ division into biaxial portions4 ,ext9ction p>allel 9 sections elongat$ axis4 ,9 conv]g5t light basal sections %[ a fa9t cross :5 normal2 optical "* g5]ally 774 ,alt]ation3 ,n kn[n 9 rock-mak+ vesuvianite4 ,di/+ui%$ f3 ,,epidote 7,pi/acite7 by ! v l[ ord] int]f]5ce colors4 ,,corundum by weak] d\ble refraction4 ,,g>net 7,grossul>ite71 ,,zoisite1 & ,,apatite may be easily confus$ ) ?is m9]al & h>d to di/+ui% f x4 ,,rem>ks3 ,f\nd 9 lime/ones1 t h und]gone alt]ation by contact ) igne\s rocks1 & 9 metamorphic s*i/s4 ,also may occur 9 d5se 7nephrite-l7 aggregates 9 s]p5t9e4 ,x is insoluble 9 hydro*loric acid4 ,h41 #f4e4 ,sp4 gr41 #c4c to #c4h4 ,,melilite4 ,,anisotropic4 ,,uniaxial4 ,,tetragonal4 ,,composition3 ,na#b7;,ca1,mg7#aa7;,al1,fe7#d,si#i,o#cf 84 a4 ,,elongation c4 ,usual ,appe>ance 9 ,sections3 ,almo/ colorless1 tabul> 7 base7 cry/als or irregul> gra9s or %r$s4 ,sections v commonly la?-%ap$1 & (t5 *>act]iz$ by ! peculi> 8peg-/ructure10#hd ! l9es or m>k+s be+ 7 elongation ( ! section74 ,index ( refraction 7n #a4fcj1 #a4fbi1 #a4fca7 high] ?an t ( ! o!r associat$ colorless mat]ials1 h5ce relief r m>k$4 ,cleavage1 p>allel to base1 v imp]fect4 ,cross$ ,nicols3 ,d\ble refraction v weak 7 #j4jjc71 & dim9i%es ) a decrease ( ,al4 ,int]f]5ce colors ! l[] #a/ ord]1 grays1 etc42 anomal\s int]f]5ce colors may %[4 ,ext9ction p>allel to cleavage or ! peculi> m>k+s or l9es4 ,optical "* usually 771 b :5 poor 9 ,al 774 ,alt]ation3 ,takes place frequ5tly to a fibr\s aggregate4 ,di/+ui%$ f3 ,,nephelite & ,,feldsp> by high] relief1 %ape1 8peg-/ructure0 & usual dull appe>ance ) reflect$ light4 ,,rem>ks3 ,abundant 9 ! leucite & nephelite rocks 7associat$ ) ^! m9]als & ) augite1 p]ovskite & *rysolite71 & takes ! place ( a feldsp> 9 ! melilite-basalt4 ,x gelat9izes easily ) hydro*loric acid4 ,h41 #e4 ,sp4 gr41 #b4i4 ,,graphite4 ,,hexagonal4 ,,composition3 ,c4 ,usual ,appe>ance 9 ,sections3 ,m9ute p>ticles1 or flakes & gra9s ( irregul> %ape1 seldom cry/alliz$4 ,opaque1 & by reflect$ light1 black ) metallic lu/re4 ,di/+ui%$ f3 ,! simil>ly appe>+ ores by its insolubility 9 acids & ! possibility ( mak+ x disappe> by heat+4 ,,rem>ks3 ,graphite is widely di/ribut$ 9 ! olde/ rock =mations1 especially 9 ! s*i/s4 ,x is (t5 associat$ ) rutile & ! iron oxides4 ,graphite is n act$ on by acids4 ,h41 #a to #b4 ,sp4 gr41 #b4ji to #b4be4 ,x is burnt ) great difficulty 9 ?9 sections on plat9um foil2 b ?is te/ may v>y1 9 _m cases ! graphite 7:5 9 blad$ flakes7 n be+ consum$ ev5 aft] long heat+4 ,:5 heat$ x may exp& into worm-l =ms4 ,c>bonace\s ,matt]4--,occurs 9 opaque1 grayi%-black p>ticles hav+ no lu/re2 & is f\nd f9ely dissem9at$1 sometimes 9 l>g] aggregations1 9 clay slates1 lime/ones1 etc4 ,,hematite4 ,,hexagonal4 ,,composition3 ,fe#b,o#c4 ,usual ,appe>ance 9 ,sections3 ,irregul> scales1 m9ute gra9s or e>?y4 ,di/9ct cry/all9e =ms n (t5 obs]v$ 9 rocks4 ,opaque1 & by reflect$ light1 black ) metallic lu/re1 or r$ )\t lu/re4 ,may also be transp>5t 9 r$ t9ts4 ,no m>k$ pleo*roism obs]v$4 ,,rem>ks3 ,f\nd widely di/ribut$ 9 acid eruptive rocks1 cry/all9e s*i/s1 etc4 ,also z inclusions 9 m9]als1 & z a r$ pigm5t 9 _m rocks4 ,x is insoluble 9 hydro*loric acid1 & non-magnetic1 unless atta*$ to gra9s ( magnetite4 ,h41 #e4e to #f4e4 ,sp4 gr41 #d4i to #e4c4 ,,ilm5ite1 ,m5accanite4 ,,hexagonal4 ,,composition3 7,fe,ti7#b,o#c4 ,usual ,appe>ance 9 ,sections3 ,irregul> masses1 )\t cry/allographic outl9e1 rhomboh$ral cry/als1 or skeleton-l gr[?s4 ,also 9 br[ni%1 transluc5t mica-l =ms4 ,opaque1 & by reflect$ light1 iron-black ) metallic lu/re4 ,:5 transluc5t3 pleo*roism br[n to yell[2 d\ble refraction n v /rong2 optically 774 ,alt]ation3 ,(t5 takes place to a :iti%1 /rongly refract+1 sub/ance only slightly transp>5t1 call$ leucox5e4 ,?is alt]ation product frequ5tly develops along def9ite rhomboh$ral directions1 ,fig4 #cc ,c4 ,also a *ange to titanite or rutile may occur1 or ! ilm5ite may be surr\nd$ by ^! m9]als4 ,di/+ui%$ f3 ,,magnetite & ,,hematite4--,by :iti%1 /rongly refract+ decomposition product4 ,at times ! di/9ction may be v difficult4 ,,rem>ks3 ,ilm5ite occurs pr9cipally 9 ! soda-ri* & basic eruptive rocks4 ,! mica-l =m is limit$ to ! porphyritic eruptives4 ,! br[n pigm5t 9 ! plagioclase ( c]ta9 gabbros may be ilm5ite4 ,x is attack$ sl[ly by hot hydro*loric acid1 & ! solution :5 heat$ ) t9 becomes violet4 ,pure ilm5ite is indiff]5t t[>ds ! magnet1 h5ce /rong magnetic prop]ties w\ld indicate a mixture ) magnetite4 ,h41 #e to #f4 ,sp4 gr41 #d4e to #e4 ,,corundum4 ,,anisotropic4 ,,uniaxial4 ,,hexagonal4 ,,composition3 ,al#b,o#c4 c a4 ,usual ,appe>ance 9 ,sections3 ,pyramidal or prismatic cry/als1 gra9s or basal plates4 ,zonal /ructure or tw9n+ may be notic$4 ,colorless or ) pat*es ( blue4 ,index ( refraction high 7n #a4gff1 #a4gfj1 #a4gfi71 h5ce relief well m>k$ & surface v r\gh4 ,rhomboh$ral cleavage may %[ 9 l>g] individuals4 ,pleo*roism only m>k$ :5 color is deep4 ,cross$ ,nicols3 ,d\ble refraction weak 7 #j4jji71 l qu>tz4 ,int]f]5ce colors middle #a/ ord]1 :ite to yell[4 ,ext9ction p>allel 9 elongat$ sections4 ,optical anomalies v r>ely notic$ 9 microscopic individuals4 ,9 conv]g5t light basal sections %[ a r indi/9ct cross2 optical "* 774 ,di/+ui%$ f3 7a7 ,,apatite & ,,vesuvianite by bright] int]f]5ce colors4 7b7 ,,t\rmal9e 7light color$7 by n hav+ su* /rong absorption4 7c7 ,,cyanite by uniaxial "*4 ,corundum may ne$ to be isolat$ f ! rock 9 ord] to be det]m9$ ) c]ta9ty4 ,,rem>ks3 f\nd 9 contact metamorphic rocks1 eruptive rocks1 granul> lime/ones1 etc4 ,x is insoluble 9 hydro*loric acid4 ,:5 rock sections are gr\nd ) em]y1 c>e mu/ be tak5 n to confuse gra9s ( em]y ) corundum 9 ! rock4 ,h41 #i4 ,sp4 gr41 #c4i to #d4 ,,qu>tz4 ,,anisotropic4 ,,uniaxial4 ,,hexagonal4 ,,composition3 ,si,o#b4 c4 ,usual ,appe>ance 9 ,sections3 ,allotriomorphic 9 ! granitoid rocks1 :5 app>5tly ! la/ m9]al to =m1 ,fig4 #e4 ,m or less *emically corrod$ pyramidal cry/als 7) cross-sections six-sid$ or rhombic ) an angle ( ab\t #ajj7 9 ! porphyritic rocks4 ,r\nd$ or angul> gra9s 9 ! 8cla/ic0 rocks2 granul> mosaic 9 cry/all9e s*i/s & contact rocks1 v r>ely 9 di/9ct cry/als 9 any rocks4 ,may at times be mutually int]p5etrat$ ) an acid feldsp> 7! areas ( qu>tz & feldsp> ext+ui%+ z entire cry/als71 produc+ 8micro-pegmatitic0 /ructure1 ,fig4 #fg4 ,f9ally may appe> z pseudomorphs aft] o!r m9]als1 b may !n consi/ ( "s ( ! o!r =ms ( silica4 ,color4--,colorless1 al?\gh by reflect$ light x may appe> color$ or cl\dy if x conta9 _m inclusions4 ,index ( ,refraction4--n #a4edg 7 #a4edd1 #a4eec7 h5ce no relief & surface smoo?4 ,cleavage44--,r>ely notic$1 an important fact 9 det]m9+ qu>tz4 ,qu>tz breaks irregul>ly4 ,inclusions4--,m9ute fluid1 gas & m9]al inclusions1 (t5 9 irregul> tra9s1 are v *>act]i/ic ( qu>tz 9 granite rocks & cry/all9e s*i/s4 ,! inclusions are n s abundant 9 porphyritic rocks1 b a few glass inclusions may occur1 fill+ up 8negative0 cry/als 9 ! qu>tz4 ,rutile1 amphibole1 etc41 may occur z ne$le-l inclusions 9 qu>tz4 ,pol>iz$ ,light3 ,pleo*roism4--,none4 ,cross$ ,nicols3 ,d\ble ,refraction4--,weak 7 #j4jji74 ,int]f]5ce ,colors4--,! middle #a/ ord]1 :ite1 yell[1 etc4 ,ext9ction4--,z qu>tz is uniaxial1 basal sections rema9 d>k dur+ a complete rotation ( /age4 ,9 ! o!r sections ext9ction is n *>act]i/ic1 due to ! abs5ce ( cleavage & cry/allographic outl9es4 ,?9 sections d n %[ circul> pol>ization4 ,conv]g5t ,light3 ,basal sections %[ a d>k cross1 )\t any r+s4 ,optical "* 774 ,alt]ation3 ,does n take place1 s qu>tz always appe>s fre% & unwea!r$ 9 sections4 ,di/+ui%$ f3 7a7 ,,sanid9e 79 fre% gra9s74--,by use ( conv]g5t light4 ,feldsp> is biaxial1 or sections :i* appe> uniaxial are 774 7b7 ,,nephelite4--,by almo/ entire abs5ce ( hexagonal outl9e1 /rong] d\ble refraction1 fre%1 unwea!r$ appe>ance & 77 optical "*4 7c7 ,,iolite 7,cordi]ite71 ,,scapolite & ,,topaz4--,see "u ! latt] m9]als4 ,qu>tz may be di/+ui%$ f all silicates by be+ dissolv$ )\t residue 9 hydr(luoric acid4 ,,rem>ks3 ,qu>tz occurs widely di/ribut$1 z 9 ! great s&/one =mations4 ,x is also a *>act]i/ic m9]al ( all acidic rocks1 be+ common 9 granite1 aplite1 rhyolite1 qu>tz-porphyry1 qu>tz-diorite1 dacite1 etc4 ,qu>tz is v brittle & h5ce is a good indicator ( ! dynamic =ces :i* h affect$ ! rocks4 ,x may %[ traces ( me*anical de=mation by p]iph]al %att]+ ( ! l>g] gra9s or by 8wavy ext9ction02#he & also evid5ces ( *emical corrosion by curv$ & loop$ cont\rs4 ,9 "s diabases ! qu>tz may be surr\nd$ by a rim ( hornbl5de or augite ne$les 78qu>tz aug5074 8,catacla/ic0 qu>tz may be biaxial4 ,! 8second>y enl>gem5t0 ( qu>tz 9 cla/ic rocks may be notic$ by ! deposition ( silica 9 cry/allographic ori5tation ar\nd ! cla/ic gra9s1#hf ! new portion ext+ui%+ at ! same "t z ! core4 ,qu>tz is n attack$ by ord9>y acids4 ,h41 #g4 ,sp4 gr41 #b4f to #b4g4 ,*alc$ony4--,?is v>iety ( ,si,o#b has a radially fibr\s /ructure & %elly p>t+4 ,x may =m sphrulites1 c5tral sections ?r\gh :i* %[ a d>k cross betwe5 cross$ nicols1 or l9e cavities 9 rocks4 ,! index ( refraction is a little l[] ?an = ord9>y qu>tz4 ,! optical "* is 771 :i* mu/ be det]m9$ by a mica or gypsum plate1 a4 ,elongation a4 ,*alc$ony occurs 9 ! gr\nd mass ( v silici\s porphyritic rocks1 :i* h micr(elsitic developm5t2 & is f\nd z a second>y m9]al 9 all k9ds ( silicate rocks4 ,,tridymite4 ,usual ,appe>ance 9 ,sections3 ,?is =m ( ,si,o#b1 :i* is soluble 9 boil+ cau/ic soda1 appe>s 9 8tile-l0 aggregates ( m9ute colorless plates 7pseudo-hexagonal7 & is always second>y4 ,! refractive index is extremely l[ 7n #a4dgg71 h5ce ! surface appe>s r\gh4 ,betwe5 cross$ nicols ! int]f]5ce colors are v l[ 9 ord] 7- #j4jjb71 & ! tablets may %[ a division into diff]5t areas 7optical anomalies74 ,9 conv]g5t light an indi/9ct biaxial figure is g5]ally se54 ,,rem>ks3 ,*iefly a volcanic m9]al1 f\nd 9 rhyolite1 tra*yte & &esite4 ,commonly associat$ ) opal & *alc$ony4 ,,calcite4 ,,anisotropic4 ,,uniaxial4 ,,hexagonal4 ,,composition3 ,ca,c,o#c4 ,ca may be replac$ by small quantities ( ,mg1 ,fe1 ,mn1 etc4 a4 ,usual ,appe>ance 9 ,sections3 ,gra9s & aggregates4 ,may be fibr\s or olitic4 ,only 9 cry/als 9 c]ta9 rocks4#hg ,illu/ration3 ,,fig4 #dj4--;,calcite1 cross$ tw9 lamell1 9 granul> lime/one4 7,f ,coh547 ,tw9n+4--,polysyn!tic1 p>allel to "o or m faces ( ,r4 7#ajab74 ,v common 9 cry/all9e lime/ones1 & may h be5 produc$ by pressure or by ! gr9d+ ( ! section4 ,%[s itself betwe5 cross$ nicols z a s]ies ( light & d>k b&s1 p>allel or int]sect+1 ,fig4 #dj1 ab\t p>allel to long] diagonal ( cleavage rhombs4 ,:5 ! composition face ( ! tw9s is oblique to ! face ( ! section1 int]f]5ce colors c be se5 )\t ! analyz]4 ,color4--,colorless :5 pure1 b may appe> color$ by transmitt$ light1 due to organic pigm5ts4 ,index ( ,refraction4--n #a4fja 7 #a4dhg1 #a4fei7 h5ce ) ord9>y light relief n m>k$4 ,due to ! great v>iation 9 refractive indices ( ! two rays1 ) pol>iz$ light1 ! surface w appe> ei!r q smoo? or r r\gh1 dep5d+ ^u :i* vibration direction lies ov] ! plane ( ! pol>iz]4 ,?is m>k$ v>iation 9 appe>ance 7sometimes call$ 8tw9kl+07 s]ves z a good te/ = calcite4 ,illu/ration3 ,,fig4 #da4--;,calcite1 section p>allel to face ( rhomboh$ron1 %[+ rhomboh$ral cleavage4 7,f ,coh547 ,cleavage4--,p>allel to unit rhomboh$ron 7#ajaa71 appe>+ 9 ?9 sections z _m %>p cracks1 ^: angles ( int]section dep5d on ! position ( ! section1 ,fig4 #da4 ,newton's colors may be se5 along cleavage cracks4 ,pol>iz$ ,light3 ,pleo*roism4--,none4 ,cross$ ,nicols3 ,d\ble ,refraction4--,v /rong 7 #j4agb74 ,int]f]5ce ,colors4--,pale1 iridesc5t colors ( v high ord]4 ,ext9ction4--,z calcite is uniaxial1 basal sections rema9 d>k dur+ rotation4 ,ext9ction angles ) respect to ! cleavage cracks v>y ) ! position ( ! section4 ,conv]g5t ,light3 ,basal sections1 ev5 :5 v ?91 %[ di/9ct int]f]5ce figure1 ) cross & r+s4 ,optical "* 774 ,di/+ui%$ f3 7a7 ,o!r ,,c>bonates4--,by ease ) :i* x is attack$ by cold dilute acids1 te/ c be made on slide aft] remov+ cov]4 7b7 ,,magnesium-,,be>+ ,,calcite4--,by micro-*emical te/s4 7c7 ,,titanite 7,sph5e74--,see "u ! latt]4 ,,rem>ks3 ,calcite is v widely di/ribut$1 9 addition to ! ext5sive s$im5t>y lime/one deposits4 ,common lime/one consi/s ( d5se aggregates ( cry/all9e gra9s4 ,calcite is (t5 a second>y product ( ! lime-be>+ silicates 9 ! m basic eruptive rocks4 ,pseudomorphs ( calcite aft] oliv9e are notewor?y4 ,co>se aggregates ( calcite occur 9 ! cry/all9e s*i/s & contact rocks4 ,calcite is exce$+ly pla/ic to pressure & me*anical de=mation may be recogniz$ by curv+ ( ! cleavage cracks1 crumpl+ ( ! tw9 lamell & 8wavy0 ext9ction4 ,calcite is easily attack$ & completely dissolv$ ) eff]vesc5ce by cold dilute acids4 ,h41 #c4 ,sp4 gr41 #b4gb4 ,,dolomite4 ,,anisotropic4 ,,uniaxial4 ,,hexagonal4 ,,composition3 ,ca,mg7,,co#c7b1 :5 pure ,ca,o #cj4d1 ,mg,o #ba4g1 ,,co#b #dg4h4 ,proportions ( ,mg & ,ca v>y1 & ,fe & ,mn also occur4 4 ,usual ,appe>ance 9 ,sections3 ,9 rocks *iefly z cry/als1 ev5 d5se homog5e\s aggregates %[+ t5d5cy t[>ds cry/all9e b\nd>ies 7sac*>oidal /ructure74 ,cry/als almo/ always unit rhomboh$ron 7#ajaa7 ) t5d5cy to curv$ surfaces4 ,index ( ,refraction4--n #a4fbb 7 #a4ejc1 #a4fhb1 #j4agi71 a little high] ?an t ( calcite4 ,= v>iation 9 appe>ance ( surface ) pol>iz$ light1 see "u calcite4 ,! microscopic *>act]s are simil> to ^? ( calcite1 f :i* x may be di/+ui%$ by n be+ s easily attack$ by cold dilute acid 7te/ c be made on slide ) cov] (f71 by t5d5cy t[>ds cry/all9e b\nd>ies1 by abs5ce ( tw9 lamell 7or :5 pres5t p>allel to #b,r4 7#bjba71 h5ce ab\t p>allel to %ort] diagonals ( cleavage rhombs71 & by micro-*emical te/s4 ,! di/9ction at times may be v difficult4 ,,rem>ks3 ,occurs 9 s$im5t>y =mations & z cry/als 9 lime/one & o!r rocks4 ,9 c]ta9 rocks ! dolomite cry/als may n h a v good 8bond10 & a 8drusy0 /ructure may also be *>act]i/ic ( ! cavities betwe5 dolomite cry/als 9 rocks4 ,only slightly attack$ by cold dilute acids1 b if acid is heat$ x dissolves easily ) eff]vesc5ce4 ,,apatite4 ,,anisotropic4 ,,uniaxial4 ,,hexagonal4 ,,composition3 a4 ,,elongation a4 ,ca#e7;,cl4,f77,,po#d7c4 ,usual ,appe>ance 9 ,sections3 ,m9ute1 sl5d] hexagonal prisms1 cross-sections hav+ regul> hexagonal b\nd>ies1 ne$les1 & gra9s4 ,figs4 #ad a & #db4 ,illu/ration3 ,,fig4 #db4--;,apatite1 %[+ cross fracture1 9 nephel9e-basalt4 7,f ,coh547 ,color4--,g5]ally colorless1 seldom blui% or br[ni% 7only 9 eruptive rocks74 ,index ( ,refraction4--n #a4fce 7 #a4fcd1 #a4fcg71 h5ce relief m m>k$ ?an t ( ! colorless associat$ m9]als4 ,cleavage4--,seldom obs]v$ microscopically4 ,p>t+4--,long column> cry/als g5]ally %[ a transv]se jo9t+1 s t ! pieces may be m or less sep>at$4 ,inclusions4--,gas & fluid may be pres5t4 ,pol>iz$ ,light3 ,pleo*roism4--,none %[n by ! colorless cry/als1 ! color$ cry/als %[ /rong] absorption p>allel to 4 ,cross$ ,nicols3 ,d\ble ,refraction4--,weak 7 #j4jjc74 ,int]f]5ce ,colors4--,! l[] fir/ ord]1 g5]ally grayi%-blue or :ite4 ,ext9ction4--,z apatite is uniaxial1 basal sections rema9 d>k dur+ rotation ( /age4 ,9 all o!r sections ext9ction is p>allel to axis4 ,conv]g5t light3 ,basal sections %[ a cross1 )\t r+s4 ,optical "* 774 ,alt]ation3 ,does n usually take place1 apatite be+ f\nd p]fectly fre% 9 decompos$ rocks1 :i* is q rem>kable consid]+ its easy solubility 9 acids4 ,di/+ui%$ f3 7a7 ,,sillimanite & ,,tremolite4--,by weak d\ble refraction & elongation a4 7b7 ,,nephelite4--,by be+ relatively mu* small] & long] ?an ! nephelite cry/als1 :i* are (t5 decompos$4 ,also by high] relief & negative results ) gelat9ization te/4 7c7 ,,zircon4--,by l[] relief & mu* weak] d\ble refraction4 7d7 ,,feldsp>s 7:5 granul> & undecompos$74--,by high] relief & uniaxial int]f]5ce figure4 7e7 ,,vesuvianite & ,,zoisite4--,may be only possible by *emical te/s4 7f7 ,,corundum4--,see "u ! latt]4 ,,rem>ks3 ,f\nd 9 mo/ igne\s rocks & cry/all9e s*i/s4 ,9 ! eruptive rocks x appe>s z "o ( ! olde/ secretions f ! magma1 & h5ce is (t5 f\nd z inclusions 9 o!r m9]als1 especially biotite1 hornbl5de1 etc4 ,apatite is easily soluble 9 hydro*loric & nitric acids4 ,h41 #d4e to #e4 ,sp4 gr41 #c4ai4 ,on acc\nt ( its high sp4 gr41 apatite1 9 rock p[d]1 comes d[n 9 heavy solutions ) ! metallic m9]als1 & c be sep>at$ f !m by ! use ( a magnet4 ,?is residue c also be te/$ = phosphorus 9 ! wet way ) ammonium molybdate4 ,,nephelite1#hh ,nephel9e1 ,elolite4 ,,anisotropic4 ,,uniaxial4 ,,hexagonal4 ,,composition3 #g,na,al,si,o#d 4 ,na,al7,si,o#c7b1 ) p>tial replacem5t ( ,na by ,k4 ,usual ,appe>ance 9 ,sections3 ,nephelite 9 %ort hexagonal prisms & gra9s 9 ! y\ng] volcanic rocks1 h5ce sections rectangul> or hexagonal1 ,fig4 #dc2 elolite allotriomorphic 9 ! old] plutonic rocks4 ,color4--,colorless4 ,index ( ,refraction4--n #a4eci 7 #a4ech1 #a4edb71 h5ce no relief & surface smoo?4 ,cleavage4--,imp]fect1 p>allel to prism 7#ajaj7 & base 7#jjja74 ,m m>k$ 9 elolite ?an 9 nephelite1 especially :5 decomposition has comm5c$4 ,illu/ration3 ,,fig4 #dc4--,nephelite sections1 %[+ zonal inclusions4 7,f ,re9is*47 ,inclusions4--,microscopic ne$les ( augite1 etc41 also fluid & gas4 ,mo/ly 9 zones4 ,elolite may be mu* cl\d$ by inclusions & alt]ation products4 ,pol>iz$ ,light3 ,pleo*roism4--,none4 ,cross$ ,nicols3 ,d\ble ,refraction4--,v weak 7 #j4jjd71 may only be detect$ by us+ a te/-plate4 ,int]f]5ce ,colors4--,! l[] fir/ ord]1 grayi%-:ite1 etc41 a little l[] ?an ! feldsp> colors4 ,ext9ction4--,z ! m9]al is uniaxial1 basal sections rema9 d>k dur+ rotation ( /age4 ,9 all o!r sections ext9ction takes place & is p>allel to cleavage l9es :5 ^! appe>4 ,conv]g5t ,light3 ,basal sections %[ a broad cross1 )\t r+s4 ,optical "* 774 ,alt]ation3 ,takes place easily to fibr\s zeolites 7natrolite71 or 9 c]ta9 rocks to mica4 ,di/+ui%$ f3 ,,o!r ,,m9]als by gelat9ization te/ & /a9+ ) fu*s9e4 ,:5 pres5t 9 small int]/itial individuals 7z is (t5 ! case 9 basalts7 x is v difficult to di/+ui% )\t ?is te/2 b x mu/ be rememb]$ t o!r m9]als1 zeolites1 etc41 w also gelat9ize4 ,,qu>tz has /rong] d\ble refraction1 r>ely %[s hexagonal outl9e1 is always fre% & optically 774 ,,feldsp> is biaxial & (t5 %[s tw9n+4 ,,analcite4--,see "u ! latt]4 ,,rem>ks3 ,nephelite be>s ! same relation to elolite z sanid9e does to or?oclase4 ,x occurs only 9 ! y\ng] volcanic rocks2 ) sanid9e 9 phonolite1 ) plagioclase 9 tephrite1 )\t feldsp> 9 nephel9e-basalt1 & ) leucite 9 leucite-basalt4 ,x is n f\nd ) prim>y qu>tz4 ,elolite occurs ) or?oclase 9 elolite-sy5ite1 etc4 nephelite & elolite frequ5tly occur ) ! sodalite gr\p4 ,nephelite gelat9izes ) acids4 ,h41 #e4e to #f4 ,sp4 gr41 #b4e to #b4f4 ,,t\rmal9e1 ,s*orl4 ,,anisotropic4 ,,uniaxial4 ,,hexagonal4 ,,composition3 ,unc]ta91 a4 ,,elongation a4 ,r#ah;,b#b7,si,o#e7d4 ,r *iefly ,al1 ,k1 ,mn1 ,ca1 ,mg1 ,li4 ,usual ,appe>ance 9 ,sections3 ,/aff-l individuals1 bun*$ or 9 radiat+ aggregates1 ,fig4 #dd ,b1 or prismatic cry/als1 ,fig4 #dd ,a4 ,basal sections may be n9e-sid$4 ,color4--,v>ies greatly1 grayi%-blue1 br[n & gre5 mo/ common4 ,li-t\rmal9e 7r>e 9 rocks7 is colorless4 ,zonal /ructure may be indicat$ by diff]5ces 9 color4 ,illu/ration3 ,,fig4 #dd4--;,a1 ,t\rmal9e1 %[+ /rong absorption at "r angles to direction ( elongation 7,p plane ( vibration ( pol>iz]74 ,qu>tzite1 ,black ,hills1 ,d4 ,b1 ,t\rmal9e 9 radiate aggregate4 ,granite1 ,cornwall4 ,index ( ,refraction4--n #a4fcc 7preci\s7 to #a4fgd 7 #a4fbj to #a4fea1 #a4fdj to #a4fhe71 h5ce relief is m>k$ & surface r\gh4 ,cleavage4--,n se5 9 ?9 sections1 b irregul>1 transv]se & longitud9al cracks may appe>4 ,pol>iz$ ,light3 ,pleo*roism4--,di/9ct1 ev5 9 light color$ v>ieties1 increas+ ) ! dep? ( color4 ,! greate/ absorption takes place at "r angles to ! direction ( elongation ( ! cry/al1 ,fig4 #dd ,a4 ,! o!r m9]als hav+ ?is v /rong absorption are hornbl5de1 d>k color$ mica 7di/+ui%$ by cleavage & lamell> =m7 & allanite4 ,pleo*roic halos may be notic$ surr\nd+ inclusions4 ,cross$ ,nicols3 ,d\ble ,refraction4--,q /rong 7 #j4jag 7preci\s7 to #j4jcd74 ,int]f]5ce ,colors4--,bright upp] fir/ or second ord]1 b may n be noticeable1 due to absorption ( p>ts ( ! light4 ,ext9ction4--,z t\rmal9e is uniaxial1 basal sections rema9 d>k dur+ rotation ( /age4 ,9 all o!r sections ext9ction is p>allel to axis4 ,conv]g5t ,light3 ,cross-sections %[ a %>p cross4 ,optical "* 774 ,alt]ation3 ,does n take place4 ,di/+ui%$ f3 7a7 ,,hornbl5de4--,by abs5ce ( cleavage1 & by ! fact t ! greate/ absorption takes place at "r angles to ! longitud9al axis1 :ile 9 hornbl5de x takes place approximately p>allel to ! longitud9al axis1 or to ! cleavage l9es :i* are p>allel to ?is axis4 7b7 ,,apatite 7:5 color$74--,by /rong absorption at "r angles to longitud9al axis4 7c7 ,,corundum4--,see "u ! latt]4 ,9 "s cases :]e recognition is difficult1 *emical te/s1 to prove pres5ce ( boracic acid1 mu/ be made4 ,,rem>ks3 ,! black s*orl is ! only prim>y t\rmal9e & is f\nd 9 granitoid rocks4 ,t\rmal9e 9 o!r rocks results f 8fum>ole0 action2 h5ce occurs 9 pegmatite1 t9 & copp] ve9s1 clay deposits1 also 7light color$7 9 contact rocks & cry/all9e s*i/s4 ,! hemimorphic t]m9ations may sometimes be notic$4 ,t\rmal9e is n act$ on by acids4 ,h41 #g to #g4e4 ,sp4 gr41 #c to #c4b4 ,x c be sep>at$ f p[d]$ rock by sp4 gr4 solutions comb9$ ) magnetic me?ods4 ,,&alusite ,,anisotropic4 ,,biaxial4 ,,or?orhombic4 ,,composition3 ,al#b,si,o#e4 a4 ,,elongation a4 ,usual ,appe>ance 9 ,sections3 ,9 %ort1 r\nd$1 prismatic cry/als1 ) almo/ squ>e cross-section4 ,colorless or at times pale r$di% & spott$4 ,index ( refraction m$ium 7n #a4fcg1 #a4fcb1 #a4fdc71 h5ce relief well m>k$ & surface r\gh4 ,cleavage1 p>allel to almo/ squ>e prism1 may %[4 ,pleo*roism only m>k$ 9 color$ v>ieties1 be+ r$di% 7! direction ( elongation or cleavage74 ,c>bonace\s inclusions are *>act]i/ic1 arrang$ z 9 macroscopic specim5s 7,*ia/olite71 ,fig4 #de4 ,pleo*roic halos may surr\nd inclusions4 ,cross$ ,nicols3 ,d\ble refraction weak 7 #j4jja74 ,int]f]5ce colors middle #a/ ord]1 :ite to yell[4 ,ext9ction 9 g5]al p>allel to axis 9 longitud9al sections1 symmetrical 9 cross-sections4 ,9 conv]g5t light ,ax4 pl4 7#jaj71 ,bxa#j4 2 axial angle v l>ge 7#b;,e #ahj72 optical "* 774 ,alt]ation3 ,(t5 takes place to d5se aggregate ( mica1 :5 ! pseudomorph may be h>d to recognize4 ,di/+ui%$ f3 7a7 ,,sillimanite by mu* weak] d\ble refraction1 less elongat$ cry/als & by elongation a 7,sillimanite elong4 c74 7b7 ,,diopside by weak] d\ble refraction1 rhombic cross-section & p>allel ext9ction 9 longitud9al sections4 ,,rem>ks3 ,v *>act]i/ic ( metamorphic s*i/s & ( contact zones ( clay slates ) granite1 etc41 b n f\nd 9 rocks :i* h be5 =m$ at great pressure4 ,! &alusite gra9s may (t5 be arrang$ 9 div]g5t or f+]-l mann]4 ,may also =m p>allel gr[?s ) sillimanite4 ,x is insoluble 9 hydro*loric acid4 ,h41 #g to #g4e4 ,sp4 gr41 #c4ah4 ,illu/ration3 ,,fig4 #de4--;,*ia/olite1 %[+ *>act]i/ic c>bonace\s inclusions4 7,f ,coh547 ,illu/ration3 ,,fig4 #df4--,sillimanite aggregate1 %[+ cross fracture1 9 mica s*i/4 7,f ,coh547 ,,sillimanite1 ,fibrolite4 ,,anisotropic4 ,,biaxial4 ,,or?orhombic4 ,,composition3 ,al#b,si,o#e4 c c4 ,,elongation c4 ,usual ,appe>ance 9 ,sections3 ,long1 sl5d]1 colorless prisms or ne$les2 (t5 9 felt-l aggregates4 ,cry/als (t5 b5t4 ,index ( refraction r high 7n #a4ffd1 #a4fef1 #a4fgg71 h5ce relief m>k$4 ,transv]se fractures common1 ,fig4 #df4 ,cross$ ,nicols3 ,d\ble refraction r /rong 7 #j4jba74 ,int]f]5ce colors upp] fir/ or l[] second ord]1 r$1 purple1 blue1 etc4 ,ext9ction p>allel to prisms4 ,ax4 pl4 7#ajj71 ,bxa4 1 #b;,e #ce to #ee4 ,optical "* 774 ,di/+ui%$ f3 7a7 ,,apatite by high] ord] int]f]5ce colors & by elongation c 7apatite has elongation a74 7b7 ,,tremolite by always p>allel ext9ction & small size ( axial angle4 7c7 ,,&alusite1 see "u ! latt] m9]al4 ,,rem>ks3 ,f\nd especially 9 clay-ri* contact rocks1 gneisses & s*i/s1 (t5 occurr+ ) iolite 7cordi]ite74 ,cry/als may appe> 9 b&s4 ,x is insoluble 9 hydro*loric acid4 ,h41 #f to #g4 ,sp4 gr41 #c4bd4 ,,topaz4 ,,anisotropic4 ,,biaxial4 ,,or?orhombic4 ,,composition3 c4 ,al7,al7,o4,f#b77,si,o#d4 ,usual ,appe>ance 9 ,sections3 ,colorless cry/als ( %ort prismatic habit1 gra9s or rod-l radiat+ aggregates4 ,index ( refraction ab\t ! same z t ( calcite 7n #a4fjh to #a4fcb1 #a4fjg to #a4fbi1 #a4fah to #a4fcg71 h5ce relief m$ium4 ,cleavage p]fect1 p>allel to base1 b does n %[ z _m cracks4 ,fluid inclusions abundant4 ,cross$ ,nicols3 ,d\ble refraction weak 7 #j4jjh to #j4jaa71 ab\t ! same z t ( qu>tz4 ,int]f]5ce colors middle fir/ ord]1 :ite1 yell[1 etc4 ,ext9ction p>allel to cleavage4 ,9 conv]g5t light1 ,ax4 pl4 7#jaj71 ,bxa4 1 axial angle l>ge 7#b;,e #hf to #abf72 int]f]5ce figure obta9$ f basal sections 7i4 e41 f sections %[+ no cleavage72 optical "* 774 ,alt]ation3 ,may take place to kaol9 or muscovite1 by loss ( ,f & tak+ up ( ,h#b,o & alkalies4 ,di/+ui%$ f3 7a7 ,,qu>tz by high] relief1 cleavage & biaxial "*4 7b7 ,,sillimanite 7:5 topaz is 9 radiat+ aggregates7 by l[] refraction & d\ble refraction4 ,,rem>ks3 ,common 9 greis5 & all granite rocks conta9+ t9 ore4 ,:5 =m$ by 8fum>ole0 action 7t9 ve9s7 ! m9]al %[s rod-l radiat+ =ms4 ,x is insoluble 9 hydro*loric acid4 ,h41 #h4 ,sp4 gr41 #c4e4 ,,/aurolite4 ,,anisotropic4 ,,biaxial4 ,,or?orhombic4 ,,composition3 ,,elongation 4 ,fe7,al,o7#d7;,al,o,h77,si,o#d7b1 b v>y+1 may conta9 ,mg or ,mn4 c4 ,illu/ration3 ,,fig4 #dg4--,/aurolite1 %[+ tw9n+ at #ij b & #fj c1 also granul> qu>tz inclusions4 7,f ,re9is*47 ,usual ,appe>ance 9 ,sections3 ,%ort1 flat prisms1 :i* may be tw9n$ at #ij or #fj1 ,fig4 #dg1 or gra9s4 ,color yell[i% to r$di%-br[n4 ,index ( refraction r high 7n #a4gda1 #a4gcf1 #a4gdf71 h5ce relief m>k$ & surface r\gh4 ,cleavage1 bo? prismatic & p9acoidal1 v>iable4 ,inclusions ( m9ute qu>tz gra9s & c>bonace\s matt] f\nd 9 l>g] cry/als1 b n 9 microscopic cry/als4 ,pleo*roism di/9ct b n /rong1 %[+ r$ c 7direction ( elongation74 ,pleo*roic halos may surr\nd inclusions4 ,cross$ ,nicols3 ,d\ble refraction weak 7 #j4jaj74 ,int]f]5ce colors middle fir/ ord]1 :ite to yell[1 etc4 7ab\t l qu>tz74 ,ext9ction 9 g5]al p>allel or symmetrical 79 cross-sections7 to cleavages or cry/al outl9e4 ,9 conv]g5t light1 ,ax4 pl4 7#ajj71 ,fig4 #dh4 ,bxa4 1 axial angle l>ge 7#b;,e #ahj72 optical "* 774 ,illu/ration3 ,,fig4 #dh4--,/aurolite1 cross-section4 ,alt]ation3 ,r>ely takes place4 ,di/+ui%$ f3 ,,titanite1 see "u ! latt] m9]al4 ,,rem>ks3 ,f\nd 9 metamorphic s*i/s1 associat$ ) cyanite 7di/h5e71 iolite 7cordi]ite71 &alusite1 etc4 ,x is "o ( ! m9]als produc$ by !rmal metamorphism1 h5ce f\nd 9 rocks ( granite contact zones4 ,x does n occur 9 ! eruptive rocks or 9 s*i/s ri* 9 amphibole4 ,/aurolite is n act$ on by hydro*loric acid4 ,h41 #g to #g4e4 ,sp4 gr41 #c4d to #c4h4 ,,! ,,or?orhombic ,,pyrox5es4 ,en/atite & ,hyp]/h5e4 ,,anisotropic4 ,,biaxial4 ,,or?orhombic4 ,,composition3 7,mg4,fe7,si,o#c4 c4 ,,elongation c4 ,en/atite conta9s little1 if any1 ,fe4 ,hyp]/h5e conta9s m ,fe1 its optical *>act]s beg9n+ to %[ ) ab\t #aj p] c5t4 ,illu/ration3 ,,fig4 #di4--;,en/atite1 %[+ column> or fibr\s /ructure axis4 ,norite1 ,h>zburg4 ,usual ,appe>ance 9 ,sections3 ,irregul>ly b\nd$ individuals 7,e7 or r\nd$ prismatic-pyramidal cry/als 7,h74 ,column> or fibr\s /ructure (t5 %[s 9 7,e71 ,fig4 #di4 ,prism angle ab\t #ib4 ,outl9e ( cry/al sections v simil> to t ( monocl9ic pyrox5es4 ,tw9n+4--,n s common z 9 monocl9ic pyrox5es4 ,p>allel gr[?s ) monocl9ic pyrox5e 7diallage7 occur4#hi ,color4--,v>ies ) ,fe p] c5t41 7,e7 colorless1 7,h7 br[ni%4 ,index ( refraction4--n #a4ffe 7,e7 to #a4gbc 7,h7 7 #a4ffj to #a4gaf1 #a4fgj to #a4gbi7 7ab\t ! same z 9 monocl9ic pyrox5e71 h5ce relief m>k$ & surface r\gh4 ,cleavage4--,v>iable1 p>allel to prism 7angle #ib7 common to all pyrox5es4 ,also cleavage or p>t+ p>allel to bra*y p9acoid 7#jaj7 7prom95t7 & macro p9acoid 7#ajj74hi ,inclusions4--,p>allel ori5t$1 br[ni% plates & rods1 produc+ 8s*ill]0 /ructure on ! pr9cipal cleavage faces1 ,fig4 #ae4 ,glass inclusions abundant 9 7,h74 ,pol>iz$ ,light3 ,pleo*roism4--,almo/ abs5t 9 7,e71 b di/9ct 9 7,h71 increas+ ) ,fe p] c5t4 ,! *ange 9 color may be v m>k$1 f br[ni%-r$ to gre5i% 4 ,cross$ ,nicols3 ,d\ble ,refraction4--,weak1 mu* weak] ?an 9 ! monocl9ic pyrox5es1 increas+ ) ,fe p] c5t4 7 #j4jaj 7,e7 to #j4jac 7,h747 ,int]f]5ce ,colors4--,high] fir/ ord]1 ab\t ! same or a little high] ?an qu>tz4 ,ext9ction4--,p>allel to cleavages 9 longitud9al sections1 :i* are p>allel to a or b1 & bisect+ angles ( int]sect+ prismatic cleavages 9 basal sections4 ,conv]g5t ,light3 ,axial plane p>allel to bra*y p9acoid 7#jaj71hi i4 e41 p>allel to be/ p9acoidal cleavage4 ,bxa4 7,e71 a7,h74 ,axial angles l>ge 7#b;,e #ie to #ahj74 ,optical "* = 7,e7771 = 7,h7774 ,on acc\nt ( weak d\ble refraction ! int]f]5ce figures are n v m>k$4 ,alt]ation3 ,takes place to ba/ite1 s]p5t9e1 etc4 ,di/+ui%$ f3 ,! ,,monocl9ic ,,pyrox5es & ,,amphiboles4--,see "u ^! species4 ,,rem>ks3 ,f\nd 9 ! granul> rocks ( ! gabbro-p]idotite s]ies1 also 9 ! oliv9e basalts 7,e72 & 9 cry/als 9 porphyritic &esite 7,h74 ,^! m9]als are 9 g5]al n attack$ by acids4 ,h41 #e to #f4 ,sp4 gr41 #c4a to #c4e4 ,bronzite is ! "n give to ! v>iety conta9+ ab\t #e ,fe & hav+ ! *>act]i/ic bronzy lu/re due to inclusions4 ,ba/ite 7an alt]ation product ( ! or?orhombic pyrox5es poor 9 ,fe74--,compos$ ( fib]s1 (t5 trav]s$ by irregul> cracks4 ,color light yell[i% or gre5i% & index ( refraction ab\t ! same z ,canada balsam4 ,pleo*roism fa9t 7only se5 9 ?ick sections71 ! greate/ absorption tak+ place p>allel to ! fib]s4 ,d\ble refraction weak & ext9ction p>allel to ! fib]s4 ,axial angle l>ge & axial plane at "r angles to pr9cipal cleavage face 7#jaj74 ,! position ( ! axial plane is ! sure/ di/9ction betwe5 ba/ite & ! or?orhombic pyrox5es4 ,,*rysolite1 ,oliv9e4 ,,anisotropic4 ,,biaxial4 ,,or?orhombic4 ,,composition3 7,mg4,fe7#b,si,o#d4 ,,elongation a or c4 ,usual ,appe>ance 9 ,sections3 ,prismatic cry/als or 9 l>ge angul> fragm5ts or gra9s4 ,longitud9al sections m or less la?-%ap$1 ) po9t$ ends1 ,figs4 #ej & #ea1 cross-sections six or eight-sid$4 ,outl9es ( cry/als (t5 r\nd$ or corrod$4 ,skeleton =ms may occur1 & sometimes tw9n+ may be obs]v$4 ,illu/ration3 ,*rysolite4 ,,fig4 #ej4 ,,fig4 #ea4 ,basal section4 ,macro p9acoid section4 ,color4--,ne>ly colorless1 may be r$di% 7) high ,fe p] c5t474 ,index ( ,refraction4--n #a4fge 7 #a4ffa1 #a4fig71 h5ce relief m>k$ & surface r\gh4 ,cleavage4--,p>allel to bra*y p9acoid 7#jaj71 less di/9ct p>allel to macro p9acoid 7#ajj71 ,fig4 #ej4 ,(t5 only made visible by decomposition4 ,an irregul> fractur+ occurs1 :i* increases ) alt]ation into s]p5t9e4 ,inclusions4--,*romite1 opaque e>?s1 apatite & ! br[n plates s common 9 hyp]/h5e2 also glass & slag 79 basaltic rocks7 & fluid 79 p]idotites & oliv9fels74 ,pol>iz$ ,light3 ,pleo*roism4--,9 g5]al none1 b notic$ 9 ! r$di% v>ieties1 :5 ! absorption is a little /rong] p>allel to 4 ,cross$ ,nicols3 ,d\ble ,refraction4--,v /rong 7 #j4jcf74 ,int]f]5ce ,colors4--,r high 9 ord] 7second or ?ird71 high] ?an ! colors ( augite4 ,ext9ction4--,9 g5]al p>allel to cleavage l9es4 ,conv]g5t ,light3 ,axial plane p>allel to base 7#jja7 & always at "r angles to cleavage cracks1 ,fig4 #ea4 ,bxa4 a4 ,axial angle v l>ge 7#b;,e #ahj74 ,optical "* 774 ,alt]ation3 ,into s]p5t9e v common1#ij produc+ 8me%-0 or 8lattice-0 /ructure 7see "u s]p5t9e1 p4 #aad72 also into amphibole1 etc4 ,9 c]ta9 basaltic rocks ! rims ( gra9s may be *ang$ into g?ite81 & 9 c]ta9 gabbros ! cry/als may be surr\nd$ by a radial rim ( amphibole4 ,di/+ui%$ f3 ,light color$ ,,monocl9ic ,,pyrox5es4-- ,by ! abs5ce ( ext9ction angles1 cleavage 7! int]sect+ prismatic cleavages ( augite be+ ( equal di/9ctness71 /rong] d\ble refraction & by axial plane be+ p>allel to base1 h5ce always at "r angles to be/ cleavage 79 augite axial plane lies 9 cl9o p9acoid1 bisect+ angles ( int]sect+ prismatic cleavages74 ,also by gelat9ization ) acids4 ,,rem>ks3 ,f\nd only 9 basic rocks1 z p]idotite1 diabase1 gabbro1 norite1 basalts1 etc4 ,*rysolite 7oliv9e7 is a v brittle m9]al & %[s "u m\nta9 mak+ pressure 8catacla/ic0 /ructure4 ,*romite is a *>act]i/ic associat$ m9]al4 ,:5 n too poor 9 ,fe1 *rysolite becomes p]man5tly r$ & pleo*roic :5 /rongly heat$4 ,*rysolite is decompos$ by hydro*loric & sulphuric acids1 ) sep>ation ( gelat9\s silica4 ,h41 #f4e to #g4 ,sp4 gr41 #c4c to #c4d4 ,hyalosid]ite 7a m f]rug9\s *rysolite7 & ,fayalite 7,fe#b,si,o#d7 may be r$di% 9 sections1 & common 9 ! basic porphyritic eruptive rocks4 ,,iolite1 ,cordi]ite1 ,di*roite4 ,,anisotropic4 ,,biaxial4 ,,or?orhombic4 ,,composition3 a4 ,,elongation a4 ,mg#c7;,al4,fe7#f,si#h,o#bh4 ,usual ,appe>ance 9 ,sections3 ,gra9s1 m r>ely cry/als ( %ort prismatic habit1 :i* (t5 =m pseudo-hexagonal int]p5etration tw9s4 ,cry/als may h edges r\nd$ or corrod$4 ,colorless1 b may be blui%4 ,index ( refraction a little l[] ?an qu>tz 7n #a4eci1 #a4ece1 #a4edd71 h5ce relief l[ & surface smoo?4 ,cleavage v v>iable1 p>allel to bra*y p9acoid 7#jaj71 especially noticeable :5 decomposition has tak5 place4 ,inclusions ( sillimanite1 zircon1 rutile1 etc41 may be se54 ,pleo*roism usually n obs]v$1 b notic$ 9 blue sections 7yell[i% :ite to blue74 ,pleo*roic halos 7yell[7 surr\nd+ inclusions common1 see p4 #ei4 ,cross$ ,nicols3 ,d\ble refraction weak 7 #j4jji71 l qu>tz4 ,int]f]5ce colors middle fir/ ord]1 :ite to yell[4 ,ext9ction 9 g5]al p>allel to cleavage cracks4 ,9 conv]g5t light1 ,ax4 pl4 7#ajj71 ,bxa4 2 axial angle l>ge 7hyp]bolas only se5 )\t ellipses7 7#b;,e #fd to #aej72 optical "* 774 ,alt]ation3 ,takes place readily1 =m+ gre5i% mica-l decomposition products1 ! decomposition comm5c+ along ! crevices or ab\t ! inclusions4 ,di/+ui%$ f3 ,,qu>tz by obs]vation 9 conv]g5t light 7qu>tz is uniaxial71 decomposition & pleo*roism or pleo*roic halos4 ,! section c also be treat$ ) hydr(luosilicic acid1 :5 ! evaporat$ solution yields *>act]i/ic prismatic cry/als ( magnesium fluosilicate4 ,,rem>ks3 ,f\nd 9 gneiss1 horn/one1 granite1 granulite1 etc41 & 9 "s volcanic rocks4 ,x is (t5 associat$ ) g>net1 biotite1 sillimanite1 etc4 ,9 a ?ick section heat+ to r$ness makes ! pleo*roism m di/9ct4 ,iolite is only slightly act$ on by acids4 ,h41 #g to #g4e4 ,sp4 gr41 #b4f4 ,x is h>d to make a me*anical sep>ation f qu>tz1 on acc\nt ( simil>ity 9 sp4 gr4 ,,natrolite4 ,,anisotropic4 ,,biaxial4 ,,or?orhombic4 ,,composition3 c4 ,,elongation c4 ,na#b;,al#b,si#b,o#aj #b;,h#b,o4 ,usual ,appe>ance 9 ,sections3 ,aggregates ( colorless1 fibr\s cry/als1 :i* may h sphrulitic /ructure1 %[+ a d>k cross betwe5 cross$ nicols4 ,index ( refraction l[] ?an balsam 7n #a4dhc1 #a4dgh1 #a4dij71 h5ce 79 l>ge cry/als7 ! surface w\ld appe> r r\gh4 ,cross$ ,nicols3 ,d\ble refraction weak 7 #j4jab74 ,int]f]5ce colors ! middle fir/ ord] 7yell[1 etc471 a little high] ?an ^? ( qu>tz4 ,ext9ction p>allel to fibres4 ,optical "* 774 ,,rem>ks3 ,nev] a prim>y m9]al 9 rocks1 b f\nd 9 igne\s rocks fill+ amygdaloidal cavities1 & also z a v common alt]ation product ( sodalite1 noselite1 nephelite & acid plagioclases4 ,x gelat9izes easily ) hydro*loric acid4 ,h41 #e to #e4e4 ,sp4 gr41 #b4b4 ,,o!r ,,zeolites4 ,,composition3 ,hydr\s silicates2 ,al1 ,ca & ,na be+ ! *ief bases4 ,usual ,appe>ance 9 ,sections3 ,! =m dep5ds on ! individual m9]al species1 b ! majority appe> 9 elongat$ cry/als or fib]s4 ,!y are all colorless & mo/ ( !m h a small index ( refraction1 h5ce no relief 7prehnite has di/9ct relief74 ,cross$ ,nicols3 ,! d\ble refraction is g5]ally v weak 7betwe5 t ( nephelite & qu>tz71 giv+ v l[ ord] int]f]5ce colors 7prehnite & ?omsonite h /rong d\ble refraction74 ,,rem>ks3 ,! zeolites are always second>y m9]als 9 rocks4 ,!y gelat9ize ) hydro*loric acid4 ,,gypsum4 ,,anisotropic4 ,,biaxial4 ,,monocl9ic4 ,,composition3 ,ca,s,o#d #b;,h#b,o4 ,usual ,appe>ance 9 ,sections3 ,colorless gra9s or fib]s4 ,may be color$1 h[ev]1 by inclusions ( c>bonace\s matt]1 iron oxides1 etc4 ,index ( refraction ab\t ! same z or?oclase 7n #a4ebe1 #a4eba1 #a4eca71 h5ce no relief & surface smoo?4 ,tw9n+ lamell abundant4 ,cleavage p>allel to 7#jaj7 gives abundant cracks1 o!r cleavages may also be notic$4 ,cross$ ,nicols3 ,d\ble refraction weak 7 #j4jaj71 ! same z qu>tz4 ,int]f]5ce colors middle fir/ ord]1 :ite to yell[4 ,ext9ction p>allel to mo/ p]fect cleavage cracks 9 sections p>allel to b axis2 l>ge ext9ction angles notic$ ) ref]5ce to less p]fect cleavages4 ,9 conv]g5t light1 ,ax4 pl4 7#jaj71 i4e41 to mo/ di/9ct cleavages2 ,bxa4 7c7 #ed front2 #b;,e #ajd2 optical "* 774 ,z ! *>act]s ( gypsum are n always v m>k$ x may be necess>y to employ micro-*emical te/s4 ,,rem>ks3 ,=ms a rock by itself1 (t5 associat$ ) rock salt4 ,x also occurs z an alt]ation product ( anhydrite4 ,gypsum is soluble 9 hydro*loric acid4 ,h41 #a4e to #b4 ,sp4 gr41 #b4b to #b4d4 ,,monocl9ic ,,pyrox5es1 ,augite1 etc4 ,includ+ ! monocl9ic m9]als ( ! ,pyrox5e ,gr\p1 :i* %[ di/9ctly ! *>act]i/ic cleavage p>allel to an almo/ "r-angl$ prism4 ,,anisotropic4 ,,biaxial4 ,,monocl9ic4 ,,elongation c4#ia ,,composition3 ,r,si,o#c1 ,r ,ca1 ,mg1 ,mn1 ,fe1 ,al *iefly1 ) ! ,ca pr$om9at+ ov] ! ,mg4 ,usual ,appe>ance 9 ,sections3 ,bo? 9 cry/als & m or less irregul> gra9s1 ,figs4 #d & #ab1 ! habit v>y+ ) ! *emical composition z foll[s3 ,diopside 7,ca1 ,mg v>ieties71 long column> cry/als & gra9s4 ,augite 7ditto1 b conta9+ also ,al & ,fe71 %ort prismatic cry/als & gra9s4 ,diallage1 granul> or lamell> 7 7#ajj771 may %[ fibr\s /ructure 4 ,prism angle #hg #jf 7important 9 cross-sections74 ,sections ( cry/als ne>ly at "r angles to ! v]tical axis are octagonal or squ>e ) truncat$ corn]s1 ,figs4 #d & #ec1 :ile ^? p>allel to ! axis are la?-%ap$4 ,pyrox5e also occurs 9 skeleton cry/als & acicul> microlites 9 eruptive rocks4 ,illu/ration3 ,,fig4 #eb4--;,augite1 section p>allel to axis %[+ prismatic cleavage1 9 leucite-basal4 7,f ,coh547 ,zonal /ructure 7especially 9 augites7 may be m>k$ by diff]5ces 9 color or ext9ction1 & 9 "s basalts ! cry/als h ! 8h\r-glass0 /ructure4 ,tw9n+4--,common1 usually ! tw9n+ plane be+ ! or?o p9acoid 7#ajj74 ,tw9 lamell may be notic$4 ,int]gr[?s occur ) or?orhombic pyrox5e & amphibole4 ,color4--,f almo/ colorless ?r\gh gre5 7diopsides1 ,na pyrox5es1 etc47 to br[n 7augites72 ! r$ to br[ni%-r$ color ( c]ta9 augites has be5 consid]$ due to manganese4 ,yell[ color v r>e4 ,index ( ,refraction4--n #a4fh to #a4gb 7 #a4fga to #a4gjf1 #a4gjj to #a4gbh71 h5ce relief high & surface r\gh4 ,cleavage4--,m or less p]fect p>allel to prism ( #hg #jf4 ,cleavage cracks di/9ct & num]\s1 b n g5]ally runn+ un9t]rupt$ly ?r\gh cry/al1 ,figs4 #ab & #eb4 ,cleavage n s p]fect z t ( amphibole4 ,p>t+4--,diallage & diopside h di/9ct p>t+ p>allel to or?o p9acoid 7#ajj71 ,fig4 #ec4 ,"s cry/als may %[ p>t+ p>allel to base 7#jja74 ,inclusions4--,tabul> microscopic int]positions1 simil> to ^? 9 bronzite1 may occur 9 diallage4 ,! iron ores1 apatite1 etc41 may occur 9 augite4 ,pol>iz$ ,light3 ,illu/ration3 ,,fig4 #ec4--;,diallage1 cross-section4 ,pleo*roism4--,usually n notic$1 & 9 g5]al only appe>+ z diff]5t %ades ( ! same color4 ,9 "s cases 7diallage1 fassaite & ,na ri* augite7 well m>k$1 a & c gre5 to yell[i% gre5 & b br[ni% to r$di%-br[n2 h5ce pleo*roism n int5se 9 sections %[+ ext9ction angles4 ,:5 ,ti is pres5t1 violet p>allel to b4 ,cross$ ,nicols3 ,d\ble ,refraction4--,/rong 7 #j4jbb to #j4jbi71 be+ /rong] 9 ! pale or colorless pyrox5es4 ,int]f]5ce ,colors4--,second ord]1 h5ce always bright t9ts4 ,ext9ction4--,symmetrical 9 sections 7?r\gh b axis7 %[+ int]sect+ cleavage l9es1 9 su* cases bisect+ ! angles ( ! cleavage4 ,9 sections %[+ p>allel cleavage l9es1 only p>allel 9 or?o p9acoid 7#ajj7 sections1 9 all o!r sections an ext9ction angle be+ obs]v$4 ,! maximum ext9ction angle is l>ge1 lies 9 ! obtuse angle1 v>ies ) ! *emical composition f #cf #cj to #ed1 & is only obta9$ :5 ! section ( ! cry/al is p>allel to ! cl9o p9acoid 7#jaj71 ,fig4 #ed1 v>y+ f ?is angle to #j1 :5 ! section is p>allel to ! or?o p9acoid 7#ajj74 ,9 ,ti & ,na pyrox5es ! incl9$ disp]sion is s great t ext9ctions are n %>p1 b in/ead a *ange takes place 9 ! int]f]5ce color f blui% to br[ni%4 ,conv]g5t ,light3 ,axial plane p>allel to cl9o p9acoid 7#jaj74 ,fig4 #ed4 ,a cleavage flake p>allel to or?o p9acoid 7#ajj7 %[s ! em]g5ce ( an optic axis 7or?orhombic pyrox5e p>allel to be/ p9acoidal cleavage w\ld n %[ figure74 ,bxa47c7 #cf to #ed front4 ,axial angles l>ge 7#b;,e #gj to #aab74 ,optical "* 774 ,! int]f]5ce figures are di/9ct on acc\nt ( ! /rong d\ble refraction4 ,alt]ation3 ,may take place to *lorite1 s]p5t9e or amphibole 7uralitization#ib71 dep5d+ on ! *emical composition & ! conditions produc+ ! *ange4 ,illu/ration3 ,,fig4 #ed4--;,diopside1 cl9o p9acoid section4 ,di/+ui%$ f3 7a7 ,,or?orhombic ,,pyrox5es4--,by ext9ction angle1 ! or?orhombic pyrox5es hav+ always p>allel or symmetrical ext9ction 9 sections p>allel to a1 b1 or c1 & by high] ord] int]f]5ce colors4 ,also f hyp]/h5e by abs5ce (1 or mu* fa9t]1 pleo*roism4 ,diallage & bronzite might be confus$ on acc\nt ( pron\nc$ p9acoidal p>t+1 fibr\s /ructure & inclusions2 b may be di/+ui%$ by ! pres5ce or abs5ce ( ext9ction angles & also by ! position ( ! optic axes relative to ! be/ cleavage plates4 7b7 ,,amphibole4--,see "u amphibole4 7c7 ,,epidote & ,,*rysolite 7,oliv9e74 ,:5 light color$ & granul>1 by exam9ation 9 conv]g5t light4 ,! plane ( ! optic axes is p>allel to ! cl9o p9acoid 7#jaj71 h5ce to ! longitud9al axis & prismatic cleavage cracks1 :ile 9 epidote x is at "r angles to ^! directions & 9 *rysolite p>allel to ! base4 ,also yell[ color is common 9 epidote b r>e 9 pyrox5e4 ,,rem>ks3 ,next to ! feldsp>s pryox5e is ! mo/ common con/itu5t ( ! igne\s rocks4 ,diopside & fassaite 7gre57 are f\nd 9 contact rocks2 also1 :at appe> to be ! same pyrox5es1 9 _m eruptive rocks1 z &esites1 monzonites1 etc4 ,malacolite 7light gre57 is f\nd 9 amphibolites & eclogites1 :]e x may be associat$ ) a gre5i% amphibole 7sm>agdite74 ,diallage 7blad$ & tw9n$7 occurs 9 gabbros & pyrox5ites4 ,common augite 7br[n7 is f\nd 9 ! rema9+ basic eruptive rocks4 ,9 ! s*i/s ! pyrox5e is colorless4 ,f9ally augite occurs z a second>y product result+ f ! 8magmatic resorption0 ( hornbl5de & biotite4 ,*emical corrosion & me*anical de=mation may occur4 ,! gre5 & br[n augites :5 heat$ to r$ness on plat9um foil may become r$ 9 color4 ,9 g5]al ! pyrox5es are n attack$ by acids4 ,h41 #e to #f4 ,sp4 gr41 #c4c to #c4e4 ,! sp4 gr4 ( ! pyrox5es is consid]ably high] ?an t ( ! amphiboles ( simil> composition1 h5ce me*anical sep>ations are possible4 ,acmite 7gir9e7 7,na pyrox5es74--,occur 9 gre5 or br[n1 elongat$ prismatic cry/als1 (t5 n v transp>5t & ) m>k$ pleo*roism 7l amphibole74 ,zonal color+ is common4 ,:5 zonally int]gr[n ) pyrox5e ! out] zone is gir9e4 ,! elongation is a 7di/9ction f amphibole ^: elongation is c74 ,! index ( refraction is high] ?an 9 ! o!r pyrox5es 7n #a4gib1 #a4gfc1 #a4hac7 & ! d\ble refraction /rong] 7 #j4jej74 ,! ext9ction angle is small 7#e7 & ! optical "* 7--74 ,! t]m gir9e-augite may be us$ to describe a soda1 pleo*roic augite ) a l>ge ext9ction angle4 ,^! pyrox5es are only f\nd 9 ! eruptive rocks ri* 9 alkalies1 z elolite-sy5ite1 phonolite1 c]ta9 tra*ytes1 etc42 h5ce are associat$ ) elolite1 sodalite1 leucite1 etc4 ,! small1 second g5]ation1 cry/als1 9 ! gr\nd mass ( a rock1 are always ! ri*e/ 9 ,na ( ! pyrox5es 9 t rock4 ,,amphibole1 ,hornbl5de1 etc4 ,,anisotropic4 ,,biaxial4 ,,monocl9ic4 ,,elongation c4 ,,composition3 ,r,si,o#c4 ,r ,mg1 ,ca1 ,fe *iefly also may conta9 ,al1 ,na1 ,mn4 ,! ,mg pr$om9ates ov] ! ,ca4 ,illu/ration3 ,,fig4 #ee4--;,hornbl5de1 %[+ tw9n+ betwe5 cross$ nicols1 9 amphibole-biotite-granite4 7,f ,coh547 ,usual ,appe>ance 9 ,sections3 ,bo? 9 cry/als & m or less irregul> gra9s1 (t5 fibr\s1 ,figs4 #ee & #ef1 ! habit v>y+ ) ! *emical composition z foll[s3 ,tremolite 7,mg#c;,ca7 & ,act9olite 77,mg,fe7#c;,ca v>ieties71 9 long column> to ne$le-l individuals1 ) no t]m9al planes or ) fray$ out ends4 ,may be 9 d5se aggregates4 ,p>gasite 9 well develop$ cry/als4 ,common gre5 ,hornbl5de 7alum9\s v>ieties7 9 cry/als1 compact gra9s or %r$s4 ,basaltic ,hornbl5de 7iron ri*1 alum9\s v>ieties7 9 prismatic cry/als ( v>y+ l5g?1 :i* may (t5 %[ 8magmatic resorption0 7to augite & magnetite7 ar\nd out] zone or ?r\gh\t :ole cry/al4 ,illu/ration3 ,,fig4 #ef4--;,hornbl5de1 section p>allel to axis1 %[+ prismatic cleavage1 9 hornbl5de-diorite4 7,f ,coh547 ,cry/als are simple 9 =m ( prismatic habit1 ) prism angle #abd #cj4 ,cross-sections are acutely rhombic1 g5]ally ) acute angles truncat$1 h5ce six-sid$ 7pyrox5e be+ eight-sid$74 ,longitud9al sections are la?-%ap$ & fibr\s /ructure may be notic$4 ,skeleton cry/als may also occur1 be+ v f9e 9 c]ta9 pit*/ones4 ,zonal /ructure & p>allel gr[? may be notic$ 9 ! amphiboles4 ,tw9n+4--,frequ5t1 p>allel to or?o p9acoid 7#ajj74 ,tw9s dual1 less (t5 multiple1 ,fig4 #ee4 ,int]gr[?s ) pyrox5e & biotite occur4 ,color4--,f colorless 7tremolite71 ?r\gh gre5 7act9olite1 p>gasite & hornbl5de7 to br[n 7basaltic hornbl5de74 ,yell[ 9 "s v>ieties & blui% 9 ! soda v>ieties4 ,index ( ,refraction4--n #a4fba to #a4fda 7 #a4fjg to #a4fbi1 #a4fcd to #a4fec7 7#a4gai1 9 ! basaltic hornbl5de71 h5ce relief di/9ct & surface r\gh4 ,cleavage4--,p]fect1 p>allel to prism ( #abd #cj4 ,g5]ally appe>s 9 ?9 sections z %>p cracks cr[d$ close toge!r1 ,figs4 #ef & #eg4 ,m p]fect ?an 9 pyrox5e4 ,"s ( ! long prisms 7act9olite & tremolite7 may %[ transv]se p>t+4 ,inclusions4--,! iron ores1 apatite1 etc41 may be f\nd 9 hornbl5de4 ,illu/ration3 ,,fig4 #eg4--;,hornbl5de1 cross-section4 ,pol>iz$ ,light3 ,pleo*roism4--,all color$ amphiboles %[ pleo*roism1 :i* 9 g5]al is /rong] ! d>k] ! color ( ! v>iety 7act9olite & p>gasite %[ b little74 ,! absorption is v m>k$ 9 ! hornbl5des1 be+ greate/ 9 ! g5]al direction ( ! cleavage l9es 9 longitud9al sections4 ,m>k$ diff]5ces 9 absorption are also *>act]i/ic ( ! m9]al species biotite1 t\rmal9e & allanite4 ,pleo*roic halos 7br[ni%7 surr\nd+ inclusions may be notic$4 ,cross$ ,nicols3 ,d\ble ,refraction4--,q /rong1 b a little weak] ?an 9 pyrox5e 7- #j4jai to #j4jbg74 ,f]rug9\s basaltic hornbl5de has /rong d\ble refraction 7- #j4jgb74 ,illu/ration3 ,,fig4 #eh4--;,act9olite1 cl9o p9acoid section4 ,int]f]5ce ,colors4--,second ord]1 h5ce bright t9ts1 b 9 d>k] color$ v>ieties n s noticeable z 9 pyrox5es1 due to ! /rong] absorption ( p>ts ( ! light4 ,! colors ( basaltic hornbl5de are s high t !y %[ no bright t9ts4 ,ext9ction4--,always symmetrical 9 sections 7?r\gh b axis7 %[+ int]sect+ cleavage l9es1 9 su* cases bisect+ ! angles ( ! cleavage4 ,9 sections %[+ p>allel cleavage l9es1 only p>allel 9 or?o p9acoid 7#ajj7 sections1 9 all o!r sections an ext9ction angle be+ obs]v$4 ,! maximum ext9ction angle lies 9 ! acute angle & is mu* small] ?an 9 pyrox5e1 v>y+ ) ! *emical composition f #j-bj4 ,9 hornbl5de1 act9olite & tremolite #ab-bj1 ,fig4 #eh2 9 ! basaltic hornbl5de #j-aj4 ,! maximum ext9ction angle is only obta9$ :5 ! section ( ! cry/al is p>allel to ! cl9o p9acoid 7#jaj71 v>y+ f ?is angle to #j1 :5 ! section is p>allel to ! or?o p9acoid 7#ajj74 ,conv]g5t ,light3 ,axial plane p>allel to cl9o p9acoid 7#aaj71 ,fig4 #eh4 ,bxo7c7 #j-bj beh9d4 ,axial angles l>ge 7#b;,e #gg to #ahj74 ,optical "* 774 ,p>gasite is 774 ,alt]ation3 ,may take place to *lorite1 talc1 s]p5t9e1 asbe/us1 etc41 dep5d+ on ! *emical composition4 ,amphibole frays out & becomes fibr\s dur+ alt]ation1 & may also lose color4 ,di/+ui%$ f3 7a7 ,,pyrox5e4--,by usually mu* /rong] pleo*roism 9 ! color$ v>ieties1 & by cleavage & ext9ction angle4 ,9 pyrox5e ! cleavage 7p>allel to prism ( #hg #jf7 is less p]fect2 & ! ext9ction angle is mu* l>g]1 v>y+ f #cf to #ed4 7b7 ,,biotite4--,by ! ext9ction 9 ! mica be+ always ab\t p>allel to ! cleavage4 ,bo? h /rong absorption1 b biotite %[s v slight pleo*roism 9 sections p>allel to ! cleavage1 & has only ! "o cleavage p>allel to ! base4 ,also ! biotite has l[] index ( refraction & g5]ally %[s uniaxial int]f]5ce figure4 ,colorless tremolite may be di/+ui%$ f muscovite & talc by ext9ction angles1 relief & l[] ord] int]f]5ce colors4 7c7 ,,t\rmal9e4--,by pres5ce ( cleavage1 & by ! fact t absorption is mo/ m>k$ ab\t p>allel to ! elongation 7also p>allel to cleavage l9es71 :ile 9 t\rmal9e ! absorption is /ronge/ at "r angles to ! elongation4 7d7 ,! ,,or?orhombic ,,pyrox5es4--,by ext9ction angles1 ! latt] hav+ p>allel ext9ction 9 all sections p>allel to a1 b & c1 & by prismatic cleavage ( #abd #cj4 ,pleo*roism is /rong 9 ! color$ v>ieties ( bo? species1 b 9 amphibole x appe>s m g5]ally z a v>iation ( ! same color2 :ile 9 hyp]/h5e a *ange 9 color is (t5 notic$1 f br[ni%-r$ to gre5i% p>allel to axis4 7e7 ,,sillimanite & ,,cyanite4--,see "u ! latt]4 ,,rem>ks3 ,amphibole comes next to pyrox5e 9 importance & di/ribution ( ! d>k color$ f]rug9\s rock-=m+ m9]als4 ,z a rule x occurs 9 rocks ) a l>ge p]c5tage ( ,si,o#b1 associat$ ) qu>tz & or?oclase2 :ile augite g5]ally occurs 9 rocks ( a basic nature1 associat$ ) plagioclase & little or no free ,si,o#b4 ,fur!rmore amphibole conta9s hydroxyl & is !re=e naturally f\nd 9 ! deep eruptive rocks2 its place be+ tak5 by augite 9 ! effusives4 ,by application ( heat hornbl5de *anges to augite1 :ile hydro*emical processes br+ ab\t ! opposite result 8uralitization40 ,tremolite & act9olite are f\nd 9 contact rocks & cry/all9e s*i/s1 also z a result ( ! alt]ation ( oliv9e into s]p5t9e4 ,p>gasite occurs 9 contact rocks4 ,common gre5 hornbl5de is f\nd 9 ! plutonic rocks 7,na poor & ,si,o#b ri*71 also 9 contact rocks & cry/all9e s*i/s 7amphibolites74 ,br[n hornbl5de replaces ! gre5 v>iety 9 ! basic plutonic rocks4 ,basaltic hornbl5de is f\nd 9 _m effusive rocks4 ,! hornbl5de cry/als 9 eruptive rocks1 be+ among ! fir/ =m$ con/itu5ts1 h (t5 suff]$ subsequ5t corrosion by ! magma1 giv+ rise to ! d>k bord] already m5tion$4 ,! br[n prim>y hornbl5de 9 "s rocks may be *ang$ by a process analog\s to 8uralitization0 into a gre51 re$-l hornbl5de4 ,me*anical de=mations are f\nd 9 massive & s*i/ose rocks4 ,light gre5 amphiboles1 ) weak pleo*roism1 may (t5 be color$ int5sely r$di%-br[n & made /rongly pleo*roic by heat+ to r$ness on plat9um foil4 ,9 g5]al ! amphiboles are n affect$ by acids4 ,h41 #e to #f4 ,sp4 gr41 #b4i to #c4c4 ,glaucophane1 ,arfv$sonite1 etc4 7,na ri* amphiboles74--,occur blue to blui%-gre5 9 color1 ) pleo*roism & weak] d\ble refraction ?an ! o!r amphiboles4 ,ext9ction angles v>y f #d-f 7glaucophane7 to #ad 7arfv$sonite74 ,!y are f\nd 9 contact rocks1 cry/all9e s*i/s1 eclogite1 etc4 ,= ! r>] & less kn[n memb]s ( ! amphibole gr\p1 res\rce %\ld be _h to m elaborate works4 ,uralite4--,pyrox5e alt]$ to amphibole1 hav+ ! outw>d cry/al =m ( pyrox5e & ! physical *>act]s & cleavage ( amphibole4 ,! *ange usually comm5ces on ! surface & ! uralite does n =m a s+le compact cry/al1 b consi/s ( num]\s sl5d] columns p>allel to "o ano!r4 ,^! little columns or fib]s h _! c & b axes p>allel to ! positions ( ^! axes 9 ! p>5t m9]al4 ,! color is gre5 & ! pleo*roism weak to /rong4 ,?is *ange is call$ 8uralitization0 & results f hydro*emical processes4 ,:5 ! alt]ation is n complete1 portions ( ! orig9al pyrox5e may be left1 hav+ all ! *>act]i/ic optical prop]ties ( ?is latt] m9]al4 ,an?ophyllite1 ! or?orhombic amphibole1 ) always p>allel ext9ction1 is sometimes f\nd 9 colorless to br[ni%1 blade- to rod-l aggregates 9 cry/all9e s*i/s & s]p5t9e4 ,,mica ,,gr\p4 ,,anisotropic4 ,,biaxial4 ,,monocl9ic4 ,may appe> hexagonal or or?orhombic4 ,,composition3 ,,elongation 7 cleavage7 c4 ,biotite 7black or f]ro-magnesium mica7 7,h4,k7#b7,mg4,fe7#b;,al#b7,si,o#d7c1 approx4 ,phlogopite a magnesium mica1 ne> biotite1 b conta9+ little ,fe4 ,illu/ration3 ,,fig4 #ei4--,mica4 ,a1 biotite1 %[+ hexagonal cross-section & zonal m>k+s4 ,m9ette1 ,freiburg4 ,b1 ,biotite1 %[+ /rong absorption p>allel to cleavage & also zonal m>k+ 7,p plane ( vibration ( pol>iz]74 ,m9ette1 ,cumb]l&4 ,c1 ,muscovite 9 b5t %r$s 9 gneiss4 ,muscovite 7:ite or pota% mica7 ,h#b7,k4,na7,al#c7,si,o#d7c1 ) "s replacem5t by ,mg or ,fe4 ,usual ,appe>ance 9 ,sections3 ,scales1 :i* may be not*$ or jagg$1 ) lat]al sections la?-%ap$2 or %r$s1 ,fig4 #ei ,c4 ,:5 di/9ctly cry/alliz$ 7magnesium micas7 ! ?9 hexagonal plates h plane angles ( #abj1 ,fig4 #ei ,a4 ,phlogopite cry/als may be ext5d$ 9 direction ( axis4 ,zonal /ructure n uncommon 9 ! magnesium micas1 ,fig4 #ei ,a1 :i* may also h d>k iron ore bord] l hornbl5de4 ,tw9n+4--,common1 g5]ally p>allel to base2 se5 9 sections %[+ cleavage by v>iations 9 ext9ction1 9 basal sections by di/ort$ int]f]5ce figures4 ,micas ( diff]5t k9ds (t5 associat$ toge!r 9 p>allel position1 also int]gr[n ) hornbl5de1 pyrox5e1 *lorite & qu>tz4 ,color4--,dep5ds on *emical composition4 ,biotites1 br[n1 gre5 or r$ to almo/ opaque4 ,phlogopites1 colorless or yell[i%4 ,muscovites colorless4 ,index ( ,refraction4--n #a4efd to #a4fai 7 #a4eda to #a4ehj1 #a4ege to #a4fch71 h5ce some:at m>k$ relief & surface v>ies 9 appe>ance f slightly r\gh to fairly r\gh4 ,9 pol>iz$ light ! surface appe>s r\ghe/ :5 ! cleavage cracks are p>allel to ! plane ( ! pol>iz]4 ,biotite has m m>k$ relief4 ,cleavage4--,v p]fect1 p>allel to base 7#jja71 ,fig4 #fj4 ,basal sections %[ no cleavage1 b all o!r sections %[ _m %>p1 p>allel cleavage cracks4 ,illu/ration3 ,,fig4 #fj4--;,biotite1 %[+ basal cleavage1 9 biotite-granite4 7,f ,coh574 ,= p]cussion & pressure figures1 see ref]5ce giv5 bel[4#ic ,inclusions4--,may be arrang$ p>allel to l9es ( pressure figure4 ,rutile ne$les1 t\rmal9e1 apatite1 etc41 common 9 magnesium mica4 ,zircon inclusions (t5 surr\nd$ by pleo*roic halos4 ,pol>iz$ ,light3 ,pleo*roism4--,v>ies ) ! color1 be+ v m>k$ 9 ! color$ v>ieties 7f pale yell[ to *e/nut-br[n or black74 ,! /rong absorption1 ab\t p>allel to ! cleavage l9es1 is v *>act]i/ic ( ! color$ mica1 ,fig4 #ei ,b4 ,/rong absorption is also notic$ 9 hornbl5de1 t\rmal9e & allanite4 ,absorption may ev5 be notic$ ar\nd inclusions 7pleo*roic halos7 9 colorless1 non-pleo*roic micas4 ,cleavage plates ( biotite are n pleo*roic unless ! axial angle is l>ge4 ,cross$ ,nicols3 ,d\ble ,refraction4--,v /rong 7 #j4jcd to #j4jeh74 ,int]f]5ce ,colors4--,high ord] 7?ird74 ,may be v bright 9 ?9 sections ( ! colorless micas1 & at times be s high 9 ord] z n to %[ any m>k$ color t9ts4 ,may n be noticeable 9 sections ( ! color$ v>ieties1 due to absorption ( p>ts ( ! light4 ,ext9ction4--,ab\t p>allel to cleavage l9es4 ,v small ext9ction angles may be notic$ 9 biotites4 ,basal sections ( biotite 7! approximately hexagonal mica7 usually appe> isotropic4 ,mottl$ appe>ance 7l 8,birds-eye0 maple7 *>act]i/ic1 caus$ by di/ortion ( ! flexible lam9 dur+ gr9d+4 ,mo/ noticeable 9 sections incl9$ to cleavage & ne> position ( ext9ction4 ,conv]g5t ,light3 ,axial plane#id & ,bxa1 practically at "r angles to basal cleavage2 !re=e cleavage plates always %[ well def9$ int]f]5ce figures1 g5]ally biaxial 9 "*4 ,! axial angles v>y greatly1 be+ usually small = biotite & phlogopite 7may appe> uniaxial7 & l>ge = muscovite 7#b;,e #ee to #ij74 ,optical "* = all micas 774 ,alt]ation3 ,biotites decompose q easily1 lose color & may become completely blea*$1 :i* appe>s to be due to a lea*+ out ( ! iron4 ,may also alt] to gre5 *lorite1 ) a fray+ out ( ! mica & a *ange to *loritic /ructure4 ,phlogopites may alt] to fibr\s1 scaly masses1 app>5tly *iefly talc4 8,sag5ite0 webs ( rutile may accompany ! alt]ation4 ,muscovites are *>act]iz$ by _! fre%ness1 & d n seem to suff] f wea!r+4 ,di/+ui%$ f3 7a7 ,,hornbl5de4--,magnesium mica has ext9ction ab\t p>allel to ! cleavage1 :ile hornbl5de may h ext9ction angles ( f #j to #bj4 ,bo? h /rong absorption1 b biotite %[s v slight pleo*roism 9 basal sections1 :i* also give approximately uniaxial int]f]5ce figures 9 conv]g5t light4 7b7 ,,t\rmal9e4--,magnesium mica %r$s %[ absorption p>allel to elongation1 :ile 9 t\rmal9e ! absorption is at "r angles to elongation4 ,!re is also an abs5ce ( cleavage 9 t\rmal9e4 7c7 ,,*lorite4--,by /rong d\ble refraction1 ! v high ord] colors1 h[ev]1 be+ (t5 n notic$4 ,*lorite also %[s aggregate /ructure & is almo/ always gre5i% 9 color4 7d7 ,,talc4--,:ite mica by l>ge axial angle ( scales 9 conv]g5t light & by micro-*emical te/s4 ,! di/9ction may be v difficult4 ,,rem>ks3 ,muscovite is a r>e prim>y m9]al 9 eruptive rocks1 except 9 two-mica granite1 etc4 ,z a second>y m9]al x occurs 9 d5se scaly aggregates or z pseudomorphs aft] feldsp>1 nephelite1 etc4 ,x is frequ5t 9 cry/all9e s*i/s & is probably also ! mica 9 amphibolite & eclogite4 ,phlogopite is f\nd *iefly 9 contact metamorphic lime/one2 & may be di/+ui%$ f muscovite by ne>ly uniaxial "* & less %>p cleavage4 ,biotite is mu* m widely di/ribut$1 occurr+ especially 9 eruptive rocks1 cry/all9e s*i/s & contact rocks4 ,*emical corrosion occurs 9 orig9al biotite ( porphyritic rocks1 produc+ a 8resorption bord]0 ( augite & magnetite4 ,me*anical de=mations1 produc+ b5d+ & slipp+ along 8glid+0 planes 7oblique to cleavage71 are common to all v>ieties ( mica & may produce *ange to *lorite4 ,! muscovites1 toge!r ) ! feldsp>s1 are ! mo/ *>act]i/ic m9]als ( dynamo metamorphic orig94 ,biotites & phlogopites are attack$ by sulphuric acid at high temp]atures4 ,muscovite is b slightly attack$ by acids4 ,h41 #b to #c4 ,sp4 gr41 #b4g to #c4b4 ,! specific gravity sep>ation betwe5 ! micas is difficult on acc\nt ( ! scaly nature ( ! m9]als4 ,o!r micas occur1 "s be+ alt]ation products ( ^? already describ$4 ,among ^! may be m5tion$3 ,li?ia ,mica4--,bo? light & d>k color$1 occurr+ 9 granitic rocks & (t5 only di/+ui%$ *emically f muscovite & biotite4 ,dam\rite 7,s]icite7 7hydr\s ,k mica74--,a second>y product usually 9 colorless1 f9e scaly aggregates 9 phillites1 s]icite-s*i/s1 etc4 ,,*lorite ,,gr\p4 ,embrac+ ! memb]s ( ! ,*lorite ,gr\p1 commonly occurr+ 9 rocks4 ,,anisotropic4 ,,biaxial4 ,,monocl9ic4 ,! m9]als ( ?is gr\p usually appe> uniaxial1 & cry/allize 9 "p ) hexagonal symmetry4 ,,composition3 ,may be consid]$ z isomorph\s mixtures ( ,h#d7,mg,fe7#c,si#b,o#i & ,h#d7,mg,fe7#b7;,al,fe7#b,si,o#i 7,ros5bus*74 ,usual ,appe>ance 9 ,sections3 ,m9ute1 scaly aggregates1 :i* may incl9e to radial gr\p+2 or 9 m9ute gra9s z a pigm5t 7v]idite7 9 o!r m9]als4 ,tw9n+4--,may be se5 z 9 mica4 ,color4--,g5]ally gre51 v>y+ f gre5i% :ite to d>k gre51 r>ely colorless or r$4 ,index ( ,refraction4--n #a4efg to #a4ehi 7 #a4efj to #a4ehe1 #a4ega to #a4eif71 h5ce no m>k$ relief & only slightly r\gh surface4 ,cleavage4--,l mica1 v p]fect2 p>allel to flat face1 :i* is consid]$ to be ! basal plane4 ,?is cleavage may n be notic$1 especially 9 second>y *lorite 9 rocks4 ,pol>iz$ ,light3 ,pleo*roism4--,9 gre5 & yell[ t9ts 7gre5 cleavage71 be+ m m>k$ 9 d>k color$ v>ieties4 ,basal sections are non-pleo*roic1 ! m9]al be+ practically uniaxial4 ,pleo*roic halos may be se54 ,cross$ ,nicols3 ,d\ble ,refraction4--,g5]ally v weak 7 #j4jja to #j4jaa74 ,int]f]5ce ,colors4--,v l[ fir/ ord]1 gray or :ite1 at times sc>cely notic$4 ,anomal\s colors1 h[ev]1 (t5 se5 7deep blue or br[n47 ,ext9ction4--,plates p>allel to cleavage g5]ally appe> isotropic or only %[ fa9t color4 ,9 o!r sections ext9ction is app>5tly p>allel to ! cleavage 9 ! uniaxial type1 b ext9ction angles may be notic$ :5 type is biaxial4 ,complete ext9ction may n be notic$1 due to aggregate /ructure4 ,conv]g5t ,light3 ,plates p>allel to cleavage %[1 at times1 an indi/9ct int]f]5ce cross1 :i* may op5 into two hyp]bolas1 indicat+ biaxial nature ( cry/allization4 ,ax4 pl4 7#jaj72 ,bxa4 #j to #ae2 #b;,e v>iable4 ,optical "* 774 ,di/+ui%$ f3 ,,s]p5t9e4--,by g5]al gre5 color 7s]p5t9e1 ) exception ( ,fe ri* v>iety1 is colorless71 pleo*roism & frequ5t anomal\s int]f]5ce colors2 b ! di/9ction betwe5 ^! two m9]als may be v difficult4 ,*lorite may resemble decompos$ or gre5 mica 7mica has1 h[ev]1 /rong d\ble refraction74 ,! diff]5t species 9 ! *lorite gr\p _c usually be di/+ui%$ 9 rocks4 ,,rem>ks3 ,! *lorites are ess5tially second>y m9]als1 d]iv$ f ! alum9\s silicates1 biotite1 augite1 g>net1 feldsp>1 etc4 ,!y are f\nd abundantly 9 *lorite-s*i/s1 contact rocks1 etc41 & z pigm5t 7v]idite7 9 alt]$ eruptive rocks4 ,may occur z a prim>y con/itu5t ( eruptive rocks1 (t5 9 p>allel gr[? ) biotite4 ,*lorides are act$ on by hot hydro*loric acid1 & decompos$ easily by sulphuric acid4 ,h41 #b to #c4 ,sp4 gr41 #b4f to #b4if4 ,a ?9 section heat$ to r$ness on plat9um foil loses wat] & becomes opaque4 ,f]rug9\s v>ieties are turn$ r$di%-br[n to black by heat+ 7s]p5t9e1 z x conta9s less iron1 may give negative results ) ?is te/74 ,delessite4--,f\nd 9 sphrulites1 fill+ cavities 9 amygdaloidal basic rocks1 & 9 pseudomorphs4 ,x appe>s to be mu* alt]$ to o!r m9]als4 ,,talc4 ,,anisotropic4 ,,monocl9ic 7,pseudo-,hexagonal74 ,,composition3 ,,elongation c4 ,h#b,mg#c7,si,o#c7d4 ,usual ,appe>ance 9 ,sections3 ,9 f9e scaly1 colorless aggregates4 ,sections1 cutt+ across ! scales1 w\ld %[ rod-l =ms4 ,index ( refraction only a little high] ?an balsam 7n #a4egb1 #a4eci1 #a4ehi71 h5ce no m>k$ relief & only slightly r\gh surface4 ,cleavage p]fect p>allel to base1 l mica4 ,cross$ ,nicols3 ,d\ble refraction v /rong 7 #j4jej74 ,int]f]5ce colors ?ird ord]1 l muscovite4 ,ext9ction p>allel to basal cleavage l9es4 ,9 conv]g5t light1 ,ax4 pl4 7#ajj71 ,bxa4 2 axial angle small 7#b;,e small72 optical "* 774 ,di/+ui%$ f3 ,,muscovite 7) :i* x is easily confus$7 by micro-*emical te/s1 prov+ abs5ce ( alkalies & ,al2 & (t5 by ! m aggregate /ructure ( ! talc4 ,also by small] axial angle ( scales 9 conv]g5t light4 ,,rem>ks3 ,f\nd ma9ly 9 metamorphic s*i/s1 etc41 always z a second>y product4 ,x is insoluble 9 hydro*loric acid4 ,h41 #a to #a4e4 ,sp4 gr41 #b4f to #b4h4 ,,epidote4 ,,anisotropic4 ,,biaxial4 ,,monocl9ic4 ,,elongation a or c4 ,,composition3 ,ca#b;,al#b7;,al,o,h77,si,o#d7c1 ) "s ,fe replac+ ,al4 ,usual ,appe>ance 9 ,sections3 ,column> to ?ick tabul> cry/als1 m or less elongat$ p>allel to or?o axis b1 ,fig4 #fa1 or 9 granul> aggregates4 ,illu/ration3 ,epidote4 ,,fig4 #fa4 ,,fig4 #fb4 ,or?o p9acoid section4 ,cl9o p9acoid section4 ,tw9n+4--,may occur b r>ely notic$4 ,irregul> int]p5etrations common ) o!r memb]s ( ! gr\p2 also p>allel gr[?s4 ,color4--,colorless to yell[i% 7,fe poor7 or yell[ to gre5i% to yell[-br[n 7,fe ri*74 ,index ( ,refraction4--n #a4gea b may be l[] 7 #a4gca1 #a4gfh71 h5ce relief high & surface r\gh4 ,cleavage4--,p>allel to base 7#jja71 ,figs4 #fa & #fb1 imp]fect p>allel to or?o p9acoid 7#ajj74 ,basal cleavage cracks n v num]\s & appe> p>allel to g5]al direction ( elongation4 ,pol>iz$ light3 ,pleo*roism4--,v>ies ) ! color1 be+ fa9t 9 ! light color$ v>ieties1 b /rong :5 ! color is m>k$ 7,fe ri*74 ,cross$ ,nicols3 ,d\ble ,refraction4--,v>iable1 (t5 v /rong 7 #j4jcg74 ,int]f]5ce ,colors4--,v>iable1 (t5 high 7?ird7 ord]s4 ,int]gr[?s ) o!r memb]s ( ! gr\p are cle>ly %[n by ! 8fleck$0 int]f]5ce colors4 ,ext9ction4--,p>allel to cleavage 9 sections p>allel to b axis4 ,9 o!r sections ext9ction angles v>y1 see ,fig4 #fb4 ,conv]g5t ,light3 ,axial plane 7#jaj71 i4 e41 at "r angles to ! elongation ( cry/al & cleavage cracks1 ,fig4 #fa4 ,bxa4-7a7 #c beh9d4 ,basal cleavage flakes %[ ! almo/ em]g5ce ( an optic axis4 ,axial angles v l>ge 7#b;,e #ahj74 ,optical "* 774 ,alt]ation3 ,does n take place readily4 ,di/+ui%$ f3 ,light color$ ,,monocl9ic ,,pyrox5e4--,by hav+ plane ( optic axes at "r angles to cleavage cracks & direction ( elongation2 :ile 9 pyrox5e plane ( optic axes is p>allel to p>allel prismatic cleavage cracks or bisects ! angle betwe5 int]sect+ cracks4 ,fur!rmore ! yell[ color is r>e 9 pyrox5e4 ,,rem>ks3 ,epidote is ess5tially a second>y m9]al1 result+ f ! alt]ation ( ! feldsp>s & ! f]ro-magnesium silicates4 ,x is f\nd 9 cry/all9e s*i/s 7especially ^? conta9+ hornbl5de71 gneiss1 gabbro1 diorite1 diabase1 lime-silicate horn/ones1 contact rocks1 etc4 ,epidote is p>tially decompos$ by hydro*loric acid4 ,! ,fe ri* epidote c be *ang$ to an int5se color by 8gl[+0 9 ! air4 ,h41 #f to #g4 ,sp4 gr41 #c4cb to #c4de4 ,pi$montite 7conta9+ ,mn74--,r$ 9 color4 ,v pleo*roic1 r$ to yell[4 ,f\nd 9 cry/all9e s*i/s1 ! porphyrite ( ,scotl&1 ! fam\s 8,porfido rosso antico0 ( ,egypt & 9 c]ta9 ,japanese mica s*i/s4 ,,zoisite4 ,ess5tially or?orhombic8 memb]s ( ,epidote gr\p4#ie ,,composition3 ,l epidote b )\t any ,fe4 ,usual ,appe>ance 9 ,sections3 ,simil> to epidote or 9 column> aggregates4 ,(t5 int]gr[n ) epidote4 ,di/+ui%$ f epidote by g5]al abs5ce ( color 7colorless to yell[i%7 & pleo*roism2 by slightly l[] refractive index 7n #a4fii to #a4gbj7 & by mu* weak] d\ble refraction 7 #j4jje & less74 ,! int]f]5ce colors are v l[ ord]1 gray to :ite1 b anomal\s colors are (t5 se5 7yell[ or prussian blue74 ,ext9ction is 9 g5]al p>allel to p9acoidal cleavage cracks 7except 9 cl9ozoisite74 ,! plane ( ! optic axes may be p>allel or at "r angles to cleavage cracks1 & ! optical "* is 774 ,,rem>ks3 ,g5]ally a second>y m9]al4 ,f\nd 9 cry/all9e s*i/s1 amphibolites1 contact rocks1 eclogite1 etc41 & 9 8saussurite40 ,may be h>d to di/+ui% f vesuvianite & apatite4 ,,allanite1 ,or?ite4 ,monocl9ic memb] ( ,epidote gr\p4 ,,composition3 ,l epidote b conta9+ c]ium4 ,usual ,appe>ance 9 ,sections3 ,simil> to epidote 9 =m2 b di/+ui%$ by br[n color 7may be also almo/ colorless71 /rong pleo*roism & absorption1 & m$ium to weak d\ble refraction 7 #j4jjb to #j4jcj74 ,lamell> tw9n+ cle>ly se5 on acc\nt ( oblique ext9ction4 ,:5 includ$ 9 hornbl5de & mica x is surr\nd$ by pleo*roic halos4 n #a4gh ab\t4 ,optical "* 774 ,usually p]fectly fre%4 ,,rem>ks3 ,f\nd z an accessory m9]al 9 ,si,o#b ri* eruptive rocks & connect$ cry/all9e s*i/s1 & 7light color$7 9 amphibolite & eclogite4 ,,titanite1 ,sph5e4 ,,anisotropic4 ,,biaxial4 ,,monocl9ic4 ,,composition3 ,ca,ti,si,o#e4 ,,elongation a4#if ,usual ,appe>ance 9 ,sections3 ,w$ge-%ap$ cry/als 79 ,na ri* rocks1 m prismatically develop$72 gra9s1 :i* may be elongat$2 & aggregates ( small r\nd$ p>ticles1 :i* appe> ne>ly opaque4 ,sections ( cry/als commonly acute rhombs1 ,fig4 #fc4 ,tw9n+4--,occurs1 ! tw9n+ b\nd>y bisect+ ! acute angles ( ! rhomb 7only notic$ betwe5 cross$ nicols71 ,fig4 #fd4 ,color4--,r$di%-br[n to yell[i% to colorless4 ,illu/ration3 ,,fig4 #fc4--,titanite1 %[+ acute rhombic cross-section4 ,index ( ,refraction4--n #a4ibj to #a4ifc 7 #a4hhh to #a4iac1 #a4igh to #b4jed71 h5ce relief v m>k$ & surface v r\gh4 ,cleavage4--,imp]fect & n p>allel to pr$om9ant =m1 h5ce only appe>s z a few r\gh cracks1 :i* are n p>allel to any cry/allographic b\nd>y1 ,fig4 #fc4 ,cleavage r>ely obs]v$ 9 second>y gra9s4 ,pol>iz$ ,light3 ,pleo*roism4--,v>ies ) ! color1 be+ m di/9ct 9 color$ cry/als1 yell[i% 7! light] color7 a & r$di%-br[n c4 ,sc>cely notic$ :5 ! color is light4 ,cross$ ,nicols3 ,d\ble ,refraction4--,v /rong 7 #j4jij to #j4ada74 ,illu/ration3 ,,fig4 #fd4--,titanite1 %[+ tw9n+ 9 nephel9e-sy5ite4 7,f ,coh547 ,int]f]5ce ,colors4--,v high ord]1 l ^? ( calcite4 ,due to ! fact t ! refractive indices ( two ( ! rays are v ne>ly alike1 "s sections may %[ v l[ ord] colors4 ,ext9ction4--,ext9ction angles n *>act]i/ic4 ,!re may be no complete ext9ction 9 :ite light1 ow+ to disp]sion4 ,conv]g5t ,light3 ,on acc\nt ( ! v /rong *>act]i/ic disp]sion ( ! optic axes 7 71 ! axial angle v>ies a good deal ) ! color ( ! light us$1 7,/4 ,got?>d7 #b;,e,,ia #eg1 #b;,e,tl #dg4 ,by us+ color$ glasses ?is v>iation 9 ! axial angle c be se54 ,! axial plane lies 9 ! cl9o p9acoid 7#jaj71 h5ce bisects ! obtuse angle 9 ! rhombic cross-section1 ,fig4 #fc4 ,bxa47c7 #ea front4 ,! optical "* is 774 ,alt]ation3 ,may take place4 ,di/+ui%$ f3 7a7 ,,/aurolite4--,9 conv]g5t light ! axial plane is %[n to be 9 ! %ort] diagonal ( ! rhombic cross-section1 :ile 9 /aurolite x is 9 ! long] diagonal4 7b7 ,,rutile4--,by biaxial "*4 7c7 ,,calcite4--,! light color$ titanite 7sph5e71 9 abs5ce ( tw9n+1 by high] index ( refraction4 ,titanite may easily be confus$ ) "s ( ! r>] m9]als4 ,,rem>ks3 ,titanite is always an accessory m9]al & is f\nd di/ribut$ 9 all rocks1 except ,si,o#b ri* eruptive & magnesia silicate rocks4 ,z a second>y m9]al x =ms rims ar\nd o!r titanium m9]als or pseudomorphs aft] !m & also ! pr9cipal "p ( leucox5e4 ,x is p>tly soluble 9 hot hydro*loric acid & completely decompos$ by sulphuric acid4 ,h41 #e to #e4e4 ,sp4 gr41 #c4c to #c4g4 ,9 a specific gravity sep>ation x falls ) ! f]rug9\s m9]als 7on acc\nt ( its d5sity7 & f ^! c g5]ally be sep>at$ by electromagnetic me?ods4 ,,feldsp> ,,gr\p4 ,or?oclase1 ,microcl9e & ! ,plagioclases4 ,,or?oclase4 ,,anisotropic4 ,,biaxial4 ,,monocl9ic4 ,,elongation 7 cleavage7 a4 ,,composition3 ,k,al,si#c,o#h1 ) "s replacem5t by ,na4 ,usual ,appe>ance 9 ,sections3 ,9 cry/als & gra9s4 ,9 porphyritic rocks habit ( cry/als m or less tabul> p>allel to cl9o p9acoid 7#jaj71 or rectangul> mu* ext5d$ p>allel to cl9o axis 1 ) cross-sections six-sid$1 or rectangul> to long la? %ape1 ,figs4 #fe & #ff4 ,cry/als may be *ang$ into r\nd$ or loop$ gra9s by *emical corrosion1 ,fig4 #f4 ,adul>ia cry/als m prismatically develop$1 giv+ rhombic sections4 ,dim5sions ( cry/als v>y extremely2 microlites occur1 at times =m+ sphrulitic /ructure4 ,! v f9e gra9$ gr\nd-mass 8micr(elsite0 7n resolv$ by ! microscope7 consi/s l>gely ( feldsp>4 ,illu/ration3 ,or?oclase cleavage plates4 ,,fig4 #fe4--;,basal4 ,,fig4 #ff4--;,cl9o p9acoid4 ,int]gr[?s ) microcl9e & plagioclase common1 =m+ 8microp]?ite0 :5 lamell are microscopic4 ,may be 9 zonal =mation ) plagioclase 7! or?oclase on ! p]iph]y74 ,also int]gr[n ) qu>tz#ig =m+ 8pegmatite0 & 8micro-pegmatite10 ,fig4 #fg4 ,illu/ration3 ,,fig4 #fg4--,micro-pegmatitic /ructure1 9 granophyric qu>tz-porphyry4 7,f ,coh547 ,zonal /ructure (t5 se51 ,fig4 #bj1 especially :5 decomposition has comm5c$2 & 9 fre% cry/als may be indicat$ by zonal arrangem5t ( inclusions4 ,tw9n+4--,v common1 g5]ally aft] ,c>lsbad law1 ,figs4 #ah & #fi2 ! tw9n+ b\nd>y1 divid+ ! section longitud9ally1 ei!r be+ p>allel to edges ( cry/al or b5t or jagg$4 ,tw9n+ aft] ,bav5o 7tw9n+ b\nd>y diagonal1 ) ! two p>ts ext+ui%+ at ! same "t1 b hav+ a & c directions cross$ 9 ! two portions7 & ,maneba* laws less common4#ih ,illu/ration3 ,,fig4 #fh4--,or?oclase1 or?o p9acoid section %[+ cleavages int]sect+ at #ij1 9 augite-sy5ite4 ,color4--,colorless or t+$ by oxide ( iron4 ,cl\dy if decompos$4 ,index ( ,refraction4--n #a4ebc 7 #a4eai1 #a4ebf71 h5ce no relief & surface smoo?4 ,cleavage4--,v>ies & sometimes only se5 9 v ?9 sections1 b is an important "* & %\ld always be se>*$ =4 ,x occurs p]fect1 p>allel to base 7#jja71 & almo/ z p]fect p>allel to cl9o p9acoid 7#jaj74 ,! two cleavages int]sect at #ij 9 section p>allel to ! b axis1 ,fig4 #fh4 ,inclusions4--,may be pres5t & arrang$ 9 regul> or zonal ord]1 b n important4 ,d n occur 9 individuals ( a second g5]ation4 ,pol>iz$ ,light3 ,pleo*roism4--,none4 ,cross$ ,nicols3 ,d\ble ,refraction4--,v weak 7 #j4jjg74 ,int]f]5ce ,colors4--,l[] fir/ ord]1 gray1 :ite1 etc41 n q s bright z colors ( qu>tz & plagioclase4 ,ext9ction4--,be+ monocl9ic ! ext9ction angle on base 7#jja71 ) ref]5ce to cl9o p9acoid 7#jaj7 cleavage cracks1 is #j4 ,on cl9o p9acoid ) ref]5ce to basal cleavage cracks1 x is #e4 ,"s sections 7notably 9 glassy sanid9e gra9s7 may appe> d>k dur+ complete rotation4 ,?is is due to ! fact t ! axial angle is v small & ! sections act approximately l ^? ( a uniaxial m9]al at "r angles to ! optic axis4 ,conv]g5t ,light3#ii ,plane ( optic axes 9 g5]al at "r angles to cl9o p9acoid 7#jaj7 7plane ( symmetry71 ,fig4 #fe1 h5ce p>allel to trace ( basal cleavage2 b 9 "s sanid9es p>allel to plane ( symmetry4 ,bxa 7a7 a #e above4 ,axial angles v>y1 #b;,e #abe 7or?oclase71 #j-ej 7sanid9e74#ajj ,may appe> uniaxial :5 axial angle is v small4 ,optical "* 774 ,alt]ation3 ,v common to clay1#aja muscovite1 hydr>gillite1 etc4 ,g5]ally comm5ces along ! cleavage cracks1 & :5 x has progress$ v f> ! :ole feldsp> appe>s opaque or cl\dy1 & no p]ceptible *ange may take place betwe5 cross$ nicols4 ,z decomposition is v preval5t 9 _m rocks1 ! or?oclase is r>ely cle> or pellucid4 ,epidote is (t5 =m$ :5 accessory solutions are pres5t4 ,di/+ui%$ f3 7a7 ,! o!r ,,feldsp>s & ,,melilite4--,see "u ! latt] m9]als4 7b7 ,,qu>tz4--,feldsp> is biaxial b :5 occurr+ 9 cle> glassy gra9s 7notably sanid9e71 :i* appe> uniaxial 9 conv]g5t light1 may resemble qu>tz4 ,:5 te/$ ! optical "* is 771 :ile t ( qu>tz is 774 ,,rem>ks3 ,! memb]s ( ! feldsp> gr\p are ! wide/ di/ribut$ ( ! rock-=m+ m9]als & _! recognition is ( ! utmo/ importance on acc\nt ( _! be>+ on ! sy/ematic classification ( rocks4 ,or?oclase is f\nd z an ess5tial con/itu5t 9 ! m acid plutonic & old] volcanic rocks1 z granite1 sy5ite1 tra*yte1 porphyry1 & also 9 gneiss1 cry/all9e s*i/s1 m seldom 9 contact rocks & subord9ate 9 cla/ic rocks4 ,*emical corrosion 7produc+ r\nd$ or loop$ gra9s71 ,fig4 #f1 & me*anical de=mation 7produc+ angul>1 %>p-edg$1 brok5 gra9s1 b5d+ & undulatory ext9ction#ajb71 ,fig4 #g1 occur 9 or?oclase4 ,:5 a rock conta9+ feldsp> cry/als is %att]$1 ! or?oclase breaks p>allel to basal cleavage & plagioclase p>allel to tw9n+ plane4 ,or?oclase is practically insoluble 9 acids4 ,h41 #f to #f4e4 ,sp4 gr41 #b4ef4 ,illu/ration3 ,,fig4 #fi4 --,sanid9e1 %[+ ,c>lsbad tw9 & cross-p>t+1 9 nephel9e-phonolite4 7,f ,coh547 ,sanid9e4--,?is cle>1 glassy v>iety ( or?oclase occurs 9 ! lat] eruptive rocks1 rhyolite1 tra*yte1 obsidian1 etc4 ,sanid9e (t5 has a p>t+ p>allel to or?o p9acoid 7#ajj71 :i* may be notic$ 9 sections s ?ick t ! cleavage is n se51 ,fig4 #fi4 ,9 g5]al x %[s no sign ( decomposition1 & has a small] axial angle ?an or?oclase4 ,inclusions ( glass are m abundant ?an 9 or?oclase4 ,,microcl9e4 ,,anisotropic4 ,,biaxial4 ,,tricl9ic4 ,,composition3 ,k,al,si#c,o#h4 ,usual ,appe>ance 9 ,sections3 ,z a rock con/itu5t 9 irregul> gra9s4 ,9 g5]al *>act]s l or?oclase & di/+ui%$ f x & ! plagioclases by *>act]i/ic 8gridiron0 /ructure betwe5 cross$ nicols1 result+ f ! polysyn!tic tw9n+ aft] bo? ,albite & ,p]icl9e laws1 ,fig4 #ai4 ,?is cross$ tw9n+ w %[ 9 all sections except ^? p>allel to ! bra*y p9acoid 7#jaj74 ,! lamell are g5]ally ?9n] ?an 9 ! plagioclases & m 8sp9dle-%ap$40#ajc ,fur!rmore ! r obscure tricl9ic cry/allization is %[n by an ext9ction angle ( #ae on basal cleavage plates ) ref]5ce to bra*y p9acoid 7#jaj7 cleavage l9es 7di/9ction f or?oclase1 :i* has ,o ext9ction angle74 ,,rem>ks3 ,f\nd ) or?oclase1 (t5 almo/ replac+ x1 9 granite1 sy5ite1 gneiss1 etc41 & is "o ( ! la/ m9]als to =m4 ,x is notably resi/ant to decomposition4 ,a /ructure l ! microcl9e tw9 /ructure may be produc$ 9 or?oclase by dynamic action4#ajd ,,! ,,plagioclases4 ,albite1 ,oligoclase1 ,labradorite1 ,anor?ite4 ,,anisotropic4 ,,biaxial4 ,,tricl9ic4 ,,elongation 7 ,albite tw9 lamell7 a 7except 9 anor?ite :5 x may be a or c74 ,,composition3#aje ,albite1 ,na,al,si#c,o#h4 ,oligoclase1 n7,na,al,si#c,o#h7 ,ca,al#b,si#b,o#h1 or n ,ab ,an1 n #b to #f4 ,labradorite1 ,na,al,si#c,o#h n7,ca,al#b,si#b,o#h71 or ,ab n ,an1 n #a1 #b or #c4 ,anor?ite1 ,ca,al#b,si#b,o#h4 ,usual ,appe>ance 9 ,sections3 ,mu* ! same z or?oclase4 ,la?-%ap$#ajf =ms & microlites v common1 especially 9 ! acid s]ies4 ,illu/ration3 ,,fig4 #gj4--,plagioclase1 %[+ n>r[ lamell1 9 diabase4 7,f ,coh547 ,illu/ration3 ,,fig4 #ga4--,plagioclase1 %[+ broad lamell1 9 gabbro4 7,f ,coh547 ,tw9n+4--,polysyn!tic1 aft] ,albite law1 almo/ univ]sal2 ! tw9n+ appe>+ betwe5 cross$ nicols z a s]ies ( d>k & light b&s1 b\nd$ by p>allel edges1 ,figs4 #gj & #ga4 ,! tw9 lamell are p>allel to bra*y p9acoid 7#jaj71 h5ce n obs]v$ 9 sections p>allel to ?is p9acoid4 ,! lamell may appe> irregul> & int]rupt$1 & seem to be broad] 9 ! basic ?an 9 ! acid s]ies4 ,:5 ?is tw9n+ fails1 h[ev]1 z 9 ! basic plagioclases 9 c]ta9 metamorphic rocks1 ! det]m9ation becomes v difficult4 ,9 "s cases polysyn!tic tw9n+1 aft] bo? ,albite & ,p]icl9e laws1 may take place at ! same "t1 giv+ rise to a /ructure some:at simil> to t ( microcl9e1 ,fig4 #gb4 ,9 addition ! polysyn!tic cry/als may be tw9n$ l or?oclase aft] ,c>lsbad & ,bav5o laws4 ,! g5]al *>act]s are ! same z 9 or?oclase ) ! foll[+ diff]5ces3 ,indices ( ,refraction3 n #a4ece 7 #a4ecb1 #a4edj7 ,albite4 n #a4eda 7 #a4ecg1 #a4ede7 ,oligoclase1 ,ab#d;,an#a4 n #a4eei 7 #a4eee4 #a4efc7 ,labradorite1 ,ab#a;,an#a4 n #a4ehb 7 #a4ege1 #a4ehh7 ,anor?ite4 ,! surface ( anor?ite appe>s slightly r\gh] ?an t ( or?oclase4 ,cleavages1 p>allel to base 7#jja7 & bra*y p9acoid 7#jaj71 nev] int]sect at "r angles1 z is ! case 9 sections ( or?oclase p>allel to b axis4 ,?is is due to ! tricl9ic sy/em ( cry/allization1 b ! div]g5ce f a "r angle is small 7#ic #cf to #id #aj74 ,illu/ration3 ,,fig4 #gb4--,plagioclase1 %[+ cross$ lamell1 9 oliv9e-gabbro4 7,f ,coh547 ,inclusions at times may be q important1 z ! vitre\s inclusions ( oligoclase 9 &esites1 etc41 & ! iron ore inclusions & o!r microlites 9 labradorite4 ,! arrangem5t ( ^! inclusions may be zonal or 9 p>allel ori5tation4 ,d\ble refraction is a little /rong] ?an = or?oclase 7 #j4jjh to #j4jac 7anor?ite771 h5ce produc+ slightly bright] int]f]5ce colors 9 sections ( ! same ?ickness4 ,ext9ction takes place 9 all sections unsymmetrically ) respect to cry/allographic1 tw9n+ or cleavage l9es 7z ^! m9]als are tricl9ic72 h5ce ext9ction angles are always obs]v$4 ,conv]g5t ,light3 ,all plagioclases %[ ! em]g5ce ( a bisectrix1#ajg m or less oblique1 on bra*y p9acoid 7#jaj7 cleavage faces4 ,^! cleavage faces %[ no tw9 lamell1 unless tw9n+ aft] ,p]icl9e law occurs1 9 :i* case ! det]m9ation is mu* m complicat$4 ,! axial angle is l>ge1 #b;,e #aee 7,albite74 ,optical "*1 dep5d+ on v>iety1 77 or 774 ,alt]ation3 ,p>tly ! same z 9 or?oclase1 =m+ clay1 muscovite1 etc4 ,calcite & epidote are m common z side-products1 & zeolitization also occurs 9 "s rocks4 ,! plagioclases decompose m easily ?an or?oclase4 ,di/+ui%$ f3 7a7 ,,or?oclase4--,by repeat$ tw9n+ aft] ,albite law1 giv+ betwe5 cross$ nicols a s]ies ( alt]nate d>k & light b&s4 ,:5 ,albite tw9n+ is abs5t ! di/9ction is v difficult4 7b7 ,,microcl9e4--,by common abs5ce ( ! microcl9e 8gridiron0 /ructure betwe5 cross$ nicols4 ,me?ods = ,optical ,det]m9ation ( ! ,plagioclases4#ajh ,! correct det]m9ation ( ! p>ticul> plagioclase is ( ! greate/ importance 9 ! classification ( rocks1 & x is no long] suffici5t to simply det]m9e ! feldsp> z ei!r or?oclase or plagioclase4 ,a quantitative analysis ( isolat$ mat]ial w\ld lead mo/ surely to ! desir$ result1 b has _m objections4 ,mod]n optical me?ods n[ p]mit ( a v accurate & conv5i5t det]m9ation "u ord9>y circum/ances4 ,b ( c\rse ^! me?ods involve a k ( ! approximate ori5tation ( ! section te/$4 ,:5 ?is section is n a def9ite cleavage fragm5t1 its ori5tation c be/ be det]m9$ by conv]g5t light te/s4 ,only an outl9e ( ^! me?ods c be "h giv51 & ref]5ce %\ld be made to m complete works = an elaborate discussion ( ! subject4 ,x is v conv5i5t to h at h& a set ( glass models ( ! plagioclases1 %[+ location ( plane ( optic axes1 vibration directions & cry/al axes4#aji 7#a7 ,s*u/]'s me?od ( recogniz+ ! diff]5t feldsp>s by ext9ction angles measur$ on ! cleavage plates#aaj is v precise1 b n always applicable = cry/als 9 rock sections4 ,,ext9ction ,,angles3 ,,ext9ction ,,angles3 ,,on ,,base1 ,,measur$ ,,f ,,trace ,,( ,,on ,,bra*y ,,p9acoid1 ,,measur$ ,,f ,,p9acoidal ,,cleavage4 ,,trace ,,( ,,basal ,,cleavage4 ,albite #d ,albite #ai ,oligoclase1 ,ab#d;,an#a #b ,oligoclase1 ,ab#d;,an#a #h ,labradorite1 ,ab#a;,an#a #e ,labradorite1 ,ab#a;,an#a #bj ,anor?ite #cf ,anor?ite #da ,confusion may "h arise betwe5 albite & labradorite if disreg>d be _h to signs1 b ! m acid oligoclase is readily di/+ui%$ f ! basic anor?ite4 ,by conv5tion ! angles on base & p9acoids are 77 :5 ! direction ( ext9ction has app>5tly mov$ z ! h&s ( a wat*1 ) ref]5ce to ! upp] "r h& edge 7betwe5 base & p9acoid7 ( ! cry/al4 ,:5 ! rev]se is true ! angles are 771 see ,fig4 #gc4 7#b7 ,! /ati/ical me?od ( ,mi*el ,lvy & o!rs is (t5 applicable1 especially 9 ! foll[+ case3 ,sections at "r angles to ! bra*y p9acoid 7#jaj7 & h5ce %[+ ,albite tw9n+4--,^! sections1 z ne>ly p]p5dicul> to ! lamell z possible1 are kn[n by ! %>p divid+ l9es1 by ! ext9ction angles on ea* side ( ! trace ( ! tw9n+ plane be+ approximately equal & by ! fact t ! two adjac5t lamell are ( ! same color :5 ! trace ( ! tw9n+ plane is p>allel to ! plane ( vibration ( ei!r nicol4 ,also 9 ! #de position ! lamell are exactly ! same color & ! divid+ l9es disappe>4 ,measure ! ext9ction angles 9 z _m sections ?us select$ z possible & take ! maximum value4#aaa ,?is %\ld be v close to ! maximum ext9ction angle1 :i* is a con/ant = ea* k9d ( feldsp>4 ,illu/ration3 ,,fig4 #gc4--,%[+ conv5tional signs ( ext9ction angles4 ,,maximum ,,ext9ction ,,angles ,,9 ,,sections ,,p]p5dicul> ,,to ,,albite ,,tw9s4 ,albite #af ,oligoclase1 ,ab#d;,an#a #e ,labradorite1 ,ab#a;,an#a #bg ,anor?ite #ec ,9 ! det]m9ation ( rod-l microlites1#aab oligoclase ext+ui%es almo/ p>allel to its l5g?1 :ile anor?ite may %[ ext9ction angles ( ov] #bg4 ,:5 ^! microlites %[ ,albite tw9n+ use ! me?od j describ$4 7#c7 ,f\qu's me?od#aac c be us$ :5 ! optical ori5tation ( ! section is kn[n 7z ! result ( a te/ ) conv]g5t light74 ,! ext9ction angles ( ^! kn[n sections are ( great diagno/ic importance4 ,! be/ sections are ^? at "r angles to ! two bisectrices1 & ^! may be obta9$ by rapidly te/+ ^? sections1 9 ! rock1 :i* %[ an int]f]5ce color ab\t half z high z ! maximum color 9 ! rock section1 9 ?is way avoid+ ! sections p>allel to ! optic axes4 ,hav+ f\nd su* a section1 te/ x ) a gypsum or undulation mica plate to prove :e!r ! bisectrix is a or c4 ,if a 7^! sections %[ %>p tw9n+ /riations7 measure ext9ction angle betwe5 trace ( axial plane & albite tw9n+2 if c measure ext9ction angle betwe5 trace ( axial plane & basal cleavage cracks4 ,,ext9ction ,,angles ,,9 ,,sections3#aad a1 ,,measur$ ,,f ,,albite ,,/riations4 c1 ,,measur$ ,,f ,,cleavage ,,cracks4 ,albite #gd #ai ,oligoclase1 ,ab#d;,an#a #hh #e ,labradorite1 ,ab#a;,an#a #fj #bb ,anor?ite #ee #dh ,:5 bo? ext9ction angles c be obta9$1 ! det]m9ation ( ! plagioclase is v c]ta91 b ! result _c be reg>d$ z def9ite :5 only "o is f\nd2 & ! me?od becomes m difficult z ! cry/als become small]4 ,! position ( ! axial plane %\ld be det]m9$ by conv]g5t light te/ & n simply by ! direction ( ext9ction 9 p>allel pol>iz$ light4 7#d7 ,mi*el ,lvy's me?od#aae c be employ$ :5 tw9n+ is pres5t aft] bo? ,c>lsbad & ,albite laws4 ,illu/ration3 ,,fig4 #gd4--;,ext9ction ,angles 9 ! ,zone normal to 7#jaj7 9 ,c>lsbad ,tw9s ( ! ,plagioclases4 ,! section to be te/$ %\ld be 9 ! zone p]p5dicul> to 7#jaj74 ,su* sections %[ %>p b\nd>y l9es betwe5 ! tw9 lamell &1 betwe5 cross$ nicols1 ! ,albite lamell %[ ! same int]f]5ce color :5 ! trace ( 7#jaj7 is p>allel to ! cross-wires ( ! ocul>1 & also 9 ! #de position ! lamell are ! same color & no divid+ l9es %[4 ,! two p>ts ( ! ,c>lsbad tw9 exhibit diff]5t int]f]5ce colors 9 ! #de position1 ?is diff]5ce be+ m m>k$ z ! composition approa*es t ( ,anor?ite4 ,! ext9ction angles are measur$ f ! trace ( ! ,albite tw9n+ plane 7#jaj71 pay+ reg>d to ! & signs1 & ! concurr5t s]ies ( angles are to be obta9$ f ! two p>ts ( ! ,c>lsbad tw94 ,! range ( ^! angles 7= f\r type compositions1 ,ab1 ,ab#d;,an#a1 ,ab#a;,an#a & ,an7 is giv5 9 ! accompany+ diagram = all positions ( ! section 9 ! zone normal to 7#jaj74 ,9 ! curves ( ?is diagram 7,fig4 #gd7 ! v]tical di/ances are ! ext9ction angles = e t5 degrees measur$ f ! trace ( ! ,albite tw9n+ plane1 & ! horizontal di/ances repres5t v>y+ positions ( ! section 9 ! zone normal to 7#jaj7 = e t5 degrees ( rotation f ! position to ! edge 7#ajj77jaj7 7t is axis71 ?r\gh a revolution ( #ahj to aga9 to ! same position4 ,! concurr5t angles 9 "o "p ( a ,c>lsbad tw9 are repres5t$ by a heavy l9e & 9 ! o!r "p by a brok5 l9e4 ,x w be obs]v$ t ! diff]5ce betwe5 ^! concurr5t angles is v small 9 ,albite 7#c7 & increases m>k$ly t[>ds ,anor?ite 7#fj74 ,,table ,,= ,,becke ,,me?od4#aaf ,or?oclase ,qu>tz ,microcl9e ,albite ,oligoclase1 ,ab#d;,an#a 2 ,qu>tz4 ,labradorite1 ,ab#a;,an#a ,qu>tz ,anor?ite 7#e7 ,becke's me?od may be employ$ to id5tify ! feldsp>1 by det]m9+ ! relative values ( ! indices ( refraction ( ! feldsp> gra9 :5 x lies 9 contact ) a qu>tz gra9 7be/ results7 or ) ! balsam 7n su* good results47 ,! gra9s %\ld h vibration directions 9 p>allel position4 ,o!r me?ods t may be employ$ are "h simply ref]r$ to3 ,det]m9ation 79 conv]g5t light7 ( ! em]g5ce ( an optic axis ) ref]5ce to a kn[n plane1 ! basic plagioclases %[ an optic axis ab\t p>allel to ( ! cry/al2 det]m9ation ( total reflection by ,wall]ant's total reflectomet]2 det]m9ation ( ! value ( ! mean index ( refraction ( cru%$ isolat$ gra9s by ,s*rd] van d] ,kolk's me?od2#aag det]m9ations by specific gravity sep>ations ) use ( heavy solutions1 & by *emical & micro-*emical te/s 7= ! relative am\nts ( ,k1 ,na & ,ca74#aah ,,rem>ks3 ,! plagioclases may h ! same two g5]al habits z or?oclase1 be+ glassy & colorless 9 ! y\ng] eruptive rocks1 & dull & cl\dy 9 ! granul> & porphyritic1 old]1 massive & s*i/ose rocks4 ,!y occur 9 rocks ( int]m$iate & basic composition4 ,albite is f\nd 9 granite 7commonly int]gr[n ) or?oclase71 gneiss1 etc41 & frequ5tly z a second>y con/itu5t 7second>y feldsp>#aai7 9 ! feldsp>-qu>tz mosaic ( me*anically metamorphos$ rocks4 ,x may also be pres5t 9 acid eruptive rocks4 ,oligoclase is v frequ5t 9 granite1 sy5ite1 gneiss1 diorite1 tra*yte1 &esite1 diabase1 etc42 & p>ticul>ly accompanies or?oclase4 ,labradorite is conf9$ m to ! gabbros1#abj basic eruptive rocks & cry/all9e s*i/s1 ri* 9 amphibole & pyrox5e4 ,anor?ite occurs 9 gabbros1 ! mo/ basic porphyrites1 basalts1 etc4 ,*emical corrosion & me*anical de=mation#aba may take place z 9 or?oclase4 ,anor?ite & labradorite are m or less decompos$ by hydro*loric acid1 :ile albite & oligoclase are n act$ on by ! acid4 ,especially int]e/+ is ! alt]ation ( ! plagioclase t takes place 9 gabbros1 accompani$ by 8uralitization0 ( ! pyrox5e1 =m+ 8saussurite40 ,?is consi/s ( a :ite to gre5i% confus$ aggregate1 *iefly ( zoisite1 grossul>ite1 vesuvianite1 *lorite1 second>y feldsp> 7albite71 etc4 ,anor?oclase 7a ,na ,k1 tricl9ic1 feldsp>74--,%[s betwe5 cross$ nicols int]sect+ areas ( exce$+ly f9e composite tw9 /ructure & o!rs ( homog5e\s /ructure1 produc+ a wat]y or 8moir0 appe>ance4 ,! tw9 /ructure may be only se5 9 v ?9 sections4 ,all possible k9ds ( p]?itic int]gr[? occur4 ,fur!r di/+ui%$ f or?oclase by small ext9ction angle 7#d7 on base & by small] axial angle 7#b;,e #gb to #hh74 ,replaces or?oclase 9 ! ,na ri* eruptives4 ,f\nd 9 augite-sy5ite & 8,rhomb5porphyr0 ( ,norway 7) rhombic cross-section71 acid augite-&esite ( ,pantell]ia & 9 ! porphyries ( ! ,h>tz4 ,,cyanite1 ,di/h5e4 ,,anisotropic4 ,,biaxial4 ,,tricl9ic4 ,,composition3 ,al#b,si,o#e4 ,,elongation c4 ,illu/ration3 ,,fig4 #ge4--;,cyanite1 macro p9acoid cleavage section4 ,usual ,appe>ance 9 ,sections3 ,blade-l cry/als )\t t]m9al planes1 b ) cross-section 7six-sid$7 %[+ two long p>allel edges & f\r %ort] edges2 also 9 column> aggregates4 ,tw9n+ common1 ) g5]ally tw9n+ plane p>allel to macro p9acoid 7#ajj74 ,colorless or blui% & spott$4 ,! index ( refraction is high 7n #a4gbj1 #a4gab1 #a4gbh71 h5ce relief m>k$ & surface r\gh4 ,cleavage p]fect1 p>allel to macro p9acoid 7#ajj71 appe>+ z %>p cracks1 p>allel to longe/ edges 9 cross-sections2 less di/9ct1 p>allel to bra*y p9acoid 7#jaj74 ,fibr\s p>t+ p>allel to base 7#jja71 ,fig4 #ge4 ,pleo*roism 7colorless to blue c7 n notic$ except 9 color$ cry/als4 ,cross$ ,nicols3 ,d\ble refraction q /rong 7 #j4jaf74 ,int]f]5ce colors upp] fir/ ord]1 yell[1 r$1 violet1 etc4 ,ext9ction angles obs]v$ 9 all sections 7be+ tricl9ic71 rea*+ a maximum ( #cj on macro p9acoid 7#ajj71 ,fig4 #ge4 ,ext9ction on base1 ab\t p>allel to mo/ p]fect cleavage4 ,9 conv]g5t light axial angle l>ge2 axial plane & ,bxa4 ab\t p]p5dicul> to be/ cleavage 7#ajj72 optical "* 774 ,alt]ation3 ,seldom obs]v$1 b may take place to mica4 ,di/+ui%$ f3 7a7 ,,amphibole by cleavage 7int]sect+ cleavages at #abd 9 amphibole & #ij 9 cyanite7 & by 7#ajj7 cleavage plates ( cyanite %[+ em]g5ce ( acute bisectrix4 7b7 ,,corundum by be+ biaxial4 ,di/9ction f simil> appe>+ m9]als may be difficult4 ,,rem>ks3 ,f\nd 9 gneiss1 granulite1 metamorphic s*i/s1 ecolgite1 etc41 commonly associat$ ) g>net4 ,x is n attack$ by acids4 ,h41 #e to #g4 ,sp4 gr41 #c4f4 ,,s]p5t9e4 ,,aggregate4 ,,elongation 7( fib]s7 c4 ,,composition3 ,h#d,mg#c,si#b,o#i1 ) replacem5t by ,fe4 ,usual ,appe>ance 9 ,sections3 ,d5se1 fibr\s 7*rysotile7 or scaly 7antigorite7 aggregates4 ,color4--,colorless to light gre5i%1 except ! ,fe ri* v>iety :i* is gre54 ,index ( ,refraction4--n #a4ee to #a4ef 7 #a4ef1 #a4ega = antigorite71 h5ce no relief & surface smoo?4 ,pol>iz$ ,light3 ,pleo*roism4--,n se5 or v feeble1 except 9 ! ,fe ri* v>iety4 ,cross$ ,nicols3 ,d\ble ,refraction4--,r weak 7 #j4jji to #j4jaa74 ,int]f]5ce ,colors4--,middle fir/ ord]1 gray1 :ite1 yell[1 etc4 ,anomal\s colors d n appe>4 ,! aggregate /ructure is di/9ctly se5 betwe5 cross$ nicols4 ,due to comp5sation aggregates may appe> isotropic4 ,di/+ui%$ f3 ,,*lorite4--,by m usual abs5ce ( color1 pleo*roism & anomal\s int]f]5ce colors2 b ?is di/9ction may be v difficult4 ,,rem>ks3 ,s]p5t9e 7bo? antigorite & *rysotile7 is ess5tially a second>y m9]al1 result+ 9 mo/ cases f ! alt]ation ( *rysolite 7oliv9e71 ,fig4 #bb1 m r>ely ( pyrox5e or amphibole4#abb ,! alt]ation ( oliv9e to antigorite leads to ! *>act]i/ic 8lattice /ructure10 ! alt]ation to *rysotile to 8me% /ructure40 ,9 ! case ( ! 8me%0 =mation ! alt]ation />ts f ! surface & cracks1 produc+ fibres ( *rysotile1 :i* /& at "r angles to ^! edges & cracks4 ,z s]p5t9ization proce$s new cracks =m1 due to increase 9 volume1 & ! process may cont9ue until complete pseudomorphism takes place4 ,:5 ?is subsequ5t s]p5t9ization ( ! me%es takes place ! result+ s]p5t9e may appe> almo/ isotropic#abc & is c]ta9ly diff]5t f ! *rysotile ( ! fir/ =m$ ve9s 7,we9s*5k74 ,pieces ( ! p>5t m9]al are (t5 pres5t4 ,s]p5t9e is f\nd 9 ophiolites1 ! alt]$ basic igne\s rocks1 pyrox5ites1 p]idotites1 etc41 & z a prim>y m9]al 9 ! ,c5tral ,alps p]idotite1 int]gr[n ) fre% oliv9e 7,we9s*5k74 ,x may also =m a rock by itself4 ,s]p5t9e is attack$ q /rongly by hydro*loric acid1 /ill m s by sulphuric acid4 ,common s]p5t9e is n alt]$ by heat+ 7di/9ction f *lorite71 b ! ,fe ri* v>iety becomes br[n & opaque4 ,h41 #b4e to #d4 ,sp4 gr41 #b4e to #b4g4 ,,clay1 ,kaol94 ,,composition3 ,,aggregate4 ,h#d;,al#b,si#b,o#i 7kaol9ite74 ,usual ,appe>ance 9 ,sections3 ,f9e1 scaly1 colorless aggregates1 :i* appe> opaque 7due to por\s /ructure74 ,! scales %[ basal cleavage4 ,index ( refraction is ab\t ! same z balsam 7n #a4ee71 h5ce no relief4 ,! d\ble refraction is weak 7 #j4jjh74 ,di/+ui%$ f3 ,colorless ,,mica & ,,hydr>gillite 7,al7,,oh7#c71 :i* z an alt]ation product ( ! feldsp>s is (t5 confus$ ) clay by weak d\ble refraction4 ,,rem>ks3 ,clay results f ! alt]ation ( ! feldsp>s 7especially ! plagioclases71 elolite1 scapolite & o!r silicates4 ,kaol9ite is insoluble 9 hydro*loric b decompos$ by sulphuric acid4 ,h41 #b4e4 ,sp4 gr41 #b4f4 ,,*apt] ,v4 ,,me?ods ,,( ,,prep>+ ,,sections4#abd ,! me?ods describ$ w be ^? us$ 9 mak+ rock sections4 ,! g5]al pr9ciples involv$ are ! same = bo? rock & cry/al sections2 al?\gh m difficulties are enc\nt]$ 9 mak+ ! latt]1 due to ! sections be+ requir$ 9 "s def9ite direction or ( "s precise ?ickness1 or on acc\nt ( ! possibly fragile or brittle "* ( ! cry/als4 ,9 ! case ( rock sections any section1 tak5 8at w0 ?r\gh ! rock1 w g5]ally d4 ,cutt+ & ,gr9d+ ,ma*9es4#abe ,_m diff]5t k9ds are us$1 ! p[] be+ furni%$ by /eam1 electric motor#abf or by ! h& or foot4 ,! *ip or fragm5t ( rock to be slic$ %\ld be comp>atively small 9 size1 & may be cut by ei!r a v]tical diamond saw or by a horizontal em]y-disc4 ,! fragm5t is held 9 position by suitable guides4 ,! moi/5$ em]y c be kept 9 ! tray & f$ to ! disc by a spoon or "s o!r device4 ,diamond saws are only ne$$ 9 ! case ( h>d rocks4 ,= cutt+ sections ( cry/als 9 def9ite directions a =m ( small h& app>atus#abg is %[n 9 ,fig4 #gf4 ,?is cut %[s h[ ! plate1 to :i* ! cry/al is cem5t$1 c be giv5 def9ite rotation 9 two directions4 ,! simpl] cry/al hold]1 appe>+ loose on ! /&1 may be us$ :5 a section is requir$ p>allel to ! face ( ! cry/al cem5t$ to ! hold]4 ,9 ^! ma*9es ! cutt+ is done ) rotat+ saws ( %eet-t91 usually *>g$ ) ei!r diamond du/ or em]y4 ,illu/ration3 ,,fig4 #gf4 ,9 ! case ( a v small cry/al a section1 p>allel to any desir$ face1 c be obta9$ by cem5t+ ?is face to a suitable frame or hold] & gr9d+ d[n by h& on a glass plate ) em]y1 ! f9al poli% be+ giv5 ) r\ge4 ,:5 ! section requir$ is n p>allel to a cry/allographic face or cleavage x mu/ be v]ifi$ geometrically ) ref]5ce to o!r faces4 ,if ! cry/als are soluble 9 wat]1 "s o!r liquid1 z bromnaph?al9 or b5z9e1 mu/ be us$ 9 gr9d+2 & v fragile cry/als are rubb$ d[n on a gr\nd glass plate )\t em]y or r\ge1 simply us+ bromnaph?al9 or "s o!r appropriate liquid4 ,:5 sections ( a cry/al are desir$ ) /rictly p>allel faces1 ! =m ( gr9d+ app>atus %[n 9 ,fig4 #gg c be us$4 ,?is app>atus consi/s ( a cyl9d]1 held )9 a suitable frame support$ on ?ree set-screws1 a#a1 a#b & a#c1 ( h>d /eel4 ,! l[] surface ( ! frame & consequ5tly ! bottom ( ! cyl9d] c be adju/$ by ! w$ge k & ! set-screws s t x is exactly p>allel to ! gr9d+ surface ( ! glass plate4 ,! cry/al to be gr\nd d[n1 p1 is cem5t$ to ! bottom ( ! cyl9d]1 & ! :ole app>atus rubb$ ov] ! gr9d+ surface ( ! plate4 ,! pressure ( ! h& on ! upp] "p ( ! cyl9d] regulates ! pressure ( ! cry/al on ! gr9d+ surface4 ,9 ?is way a surface is obta9$ :i* is exactly p>allel to ! surface cem5t$ to ! cyl9d]4 ,illu/ration3 ,,fig4 #gg4 ,sections ( def9ite ?ickness c also be obta9$ by us+ ?is app>atus2 = ! adju/m5ts ) ! w$ge k may be s arrang$ t1 :5 ! /op t 9 ! cyl9d] has rea*$ ! bottom ( ! slot 9 ! frame1 ! l[] surface ( ! cyl9d] w be ! requir$ di/ance f ! gr9d+ surface ( ! glass plate4 ,! w$ge is graduat$ s t ! value ( "o division on ! slop+ top is kn[n 9 mm4 ( v]tical di/ance4 ,saws4 ,saws1#abh ( ab\t six in*es 9 diamet] made f in* %eet-t91 are conv5i5t = g5]al "w1 & may be *>g$ ) diamond du/ by ! op]ator z foll[s3#abi ,cru% "o or two c>ats ( r\gh cry/als ( diamond-bort 9 a small /eel mort> to ab\t ! condition ( f9e s&1 c>e be+ tak5 n to r$uce ! diamond to p[d]4 ,transf] ! du/ to a piece ( flat iron &1 aft] collect+ x 9 a heap1 moi/5 ) a drop ( oil4 ,! cutt+ edge ( ! t9 disk mu/ n[ be prep>$ by mak+ a s]ies ( incisions 7 in* deep7 on ! out] m>g94 ,?is c be done by /rik+ ! disk ) a %>p1 ?9 knife edge4 ,! l>g] ! numb] ( incisions & ! clos] !y are toge!r ! bett]4 ,*>g+ ! saw is accompli%$ by g5tly hamm]+ ! edge aga9/ ! iron plate1 ^u :i* is ! pa/e ( diamond du/ & oil4 ,! disk mu/ be sl[ly rotat$ dur+ ?is *>g+ process1 :i* %\ld be cont9u$ until all portions ( ! edge h be5 gone ov] two or ?ree times4 ,in/ead ( *>g+ ) diamond du/ ! saws may be us$ ) em]y4 ,! edges ( ! saws %\ld fir/ be 8upset10 z j describ$1 & !n :ile rotat+ *>g$ ) em]y4 ,! em]y 9 ! /ate ( mud c be appli$ ) ! ?umb & f+]s1 or ! saw c be all[$ to pass ?r\gh a tray ( em]y mud4 ,! f9] grades ( em]y 7,nos4 #ajj to #abj7 %\ld be us$4 ,! me?od ( m\nt+ saws1 ( c\rse1 dep5ds on ! way ! saws & sp9dles are con/ruct$4 ,x is well1 h[ev]1 to h ! hole 9 ! c5t] ( ! saw-disk suffici5tly l>ge to all[ ( adju/m5t = accurate c5t]+4 ,cutt+4 ,dur+ ! process ( cutt+ a lubricant mu/ be us$ on ! saw4 ,petroleum has be5 recomm5d$ by "s1 b wat] seems to be ! mo/ us$4 ,hold+ a piece ( soap aga9/ ! cutt+ edge w also r$uce friction4 ,x is conv5i5t to c>ry ! wat] to ! saw ?r\gh a v small lead pipe1 :i* p]mits ( easy adju/m5t1 s t ! wat] c be deliv]$ at j ! "r spot1 ! fl[ ( wat]1 ( c\rse1 be+ regulat$ by a /op-cock4 ,ano!r me?od = cutt+ sections is us$ by ! ,u4 ,s4 ,geological ,survey at ,wa%+ton1 ,d4 ,c4 ,! app>atus consi/s ( an endless wire ( s(t iron1 ab\t in* 9 diamet]1 revolv+ ov] two pulleys or :eels1 "o ( :i* is driv5 by /eam-p[]4 ,! wire is *>g$ by dipp+ ! f+]s 9 wat]1 tak+ up a little f9e 7#abj grade7 em]y & hold+ ! f+]s aga9/ ! wire above ! section4 ,! wire revolves s z to cut d[nw>ds1 ?us c>ry+ ) x ! em]y tak5 f ! f+]s4 ,9 cutt+ sections ! ?ickness1 ( c\rse1 dep5ds on ! "* ( ! rock2 ! m por\s & fragile ! rock ! ?ick] ! section %\ld be made1 an ord9>y section be+ ab\t z ?ick z a silv] qu>t] ( a doll>4 ,v (t5 by skill & practice a suitably %ap$ *ip or fragm5t c be deta*$ f ! specim5 ) a hamm] or ) a hamm] & cleavage *isels1 ?us avoid+ ! delay & tr\ble involv$ 9 ! use ( ! section cutt]4 ,gr9d+ ,plates or ,laps4 ,copp] laps1 ab\t #g-h in*es 9 diamet] & in* ?ick1 seem to be be/ = g5]al purposes2 al?\gh laps made ( lead or ca/ iron are also us$4 ,a lead lap1 be+ s(t1 holds ! em]y well & ?us ha/5s ! gr9d+ away ( ! section2 b at ! same "t its own smoo? surface is soon de/roy$4 ,a ca/ iron lap is mu* h>d] & reta9s its smoo? surface bett]1 b does n hold ! em]y s well & !re=e ret>ds ! process ( gr9d+4 ,copp]1 be+ int]m$iate 9 h>dness betwe5 lead & iron1 seems to comb9e ! advantages ( bo?4 ,x is always good practice to h at lea/ two laps1 "o = ! prelim9>y gr9d+ ) co>se em]y & ! o!r = ! f9al gr9d+ ) ! f9e/ grades ( em]y4 ,9 ?is way "o lap is always kept ) a smoo? surface1 mak+ x possible to give a uni=m1 plane f9i% to ! section4 ,! surface ( ! laps %\ld n be exactly plane1 b turn$ or f9i%$ s z to be a little high] 7 ( an in* = diamet] ( #h in*es7 at ! axis ?an at ! p]iph]y2 ! idea be+ to comp5sate = ! m rapid abrasive action t[>ds ! p]iph]y4 ,cem5t+4 ,= gr9d+ d[n to a prop] ?9ness = transp>5cy x is necess>y to cem5t ! fragm5t ( rock to a hold]1 :i* consi/s ( a small piece ( plate-glass ab\t in* ?ick4 ,if ! piece ( rock has be5 cut by a good diamond saw ! surface w be comp>atively smoo? & uni=m1 & may only ne$ poli%+ 7describ$ "u gr9d+7 be=e cem5t+4 ,:51 h[ev]1 ! piece ( rock is 9 ! %ape ( a *ip or r\gh fragm5t x is fir/ necess>y to prep>e a smoo? gr\nd surface on "o side 7describ$ "u gr9d+7 be=e x c be cem5t$ to ! glass hold]4 ,! pieces ( plate-glass us$ %\ld be free f flaws1 bubbles or any?+ t5d+ to de/roy uni=mity ( surface1 & %\ld be a little l>g] ?an ! *ips & slices ( rock = :i* !y are to act z hold]s4 ,h>d5$ ,canada balsam1 or bett] yet1 a cem5t made ( a mixture ( %ellac & ,v5ice turp5t9e1#acj %\ld be us$4 ,! process ( cem5t+ is c>ri$ on z foll[s3 ,heat ! glass support ov] an alcohol lamp or a ,buns5 burn]1 place x on a good non-conductor ( heat1 z a piece ( wood1 & rub x ) a /ick ( ! cem5t until a suffici5t quantity has be5 melt$ (f4 ,! piece ( rock %\ld !n be treat$ 9 ! same mann]1 apply+ ! cem5t to ! smoo? f9i%$ portion4 ,c>e mu/ be tak5 t nei!r ! glass nor rock prep>ation are heat$ too mu*1 z ?is w\ld cause ! cem5t to smoke or bubble4 ,aft] plac+ ! rock prep>ation & plate toge!r1 use q a little pressure 9 ord] to drive out all sup]flu\s cem5t4 ,exam9e n[1 ?r\gh ! glass1 ! contact surface & see t x is entirely free f bubbles1 etc4 ,bubbles are usually caus$ by ov]heat+ ( ! p>ts be=e cem5t+4 ,if only v few bubbles are se51 !y may g5]ally be remov$ by mov+ ! rock prep>ation rapidly back & =? ov] ! glass plate4 ,if ! bubbles are num]\s or _c be remov$ 9 ! mann] j describ$1 ! rock prep>ation mu/ be sep>at$ f ! glass plate & ! cem5t+ done ov] aga94 ,bubbles mu/ n be all[$ to rema91 z ! portions ( ! rock ov] !m1 n hav+ any cem5t back+1 are gr\nd away leav+ holes 9 ! section4 ,gr9d+4 ,aft] ! rock prep>ation has be5 cem5t$ to its glass hold] x is ready = ! gr9d+ process1 = :i* are us$ horizontal laps1 m\nt$ on a v]tical sp9dle 9 ! tray ,t1 ,fig4 #gf4 ,! copp] lap = ! fir/ gr9d+ is put 9 place1 &1 aft] x has comm5c$ to rotate1 is *>g$ ) em]y & wat]4 ,?is c conv5i5tly be done by dropp+ on ! em]y & wat]1 ei!r ) ! f+]s or ) a small bun* ( rags at ! end ( a /ick4 ,a l>ge camel's hair bru% may be us$ = putt+ on ! f9e/ em]y4 ,! em]y is di/ribut$ ov] ! rotat+ lap by ! motion ( ! rock prep>ation dur+ gr9d+4 ,! k9d ( em]y us$ = ?is fir/ gr9d+ dep5ds some:at on ! "* ( ! rock section4 ,if ! section is compos$ ( a h>d1 compact1 f9e gra9$ rock1 ! fir/ em]y us$ may be q co>se2 ! co>s] ! em]y ! m rapid be+ ! gr9d+ d[n4 ,= r\gh1 quick "w1 ,nos4 #hj to #ajj em]y c be us$ until ! section becomes q ?92 !n1 /ill us+ ! same lap1 sub/itute ! f9e/ corn em]y 7next co>se/ to fl\r em]y7 & cont9ue gr9d+ until ! section becomes q transluc5t4 ,! lap mu/ !n be *ang$1 & ! gr9d+ f9i%$ ) ! f9e/ em]y du/4 ,too great c>e _c be giv5 to cleanl9ess :ile do+ ?is sort ( "w4 ,a s+le gra9 ( co>se em]y1 gett+ on ! lap or section dur+ ! f9al gr9d+1 w (t5 spoil ! :ole "w by mak+ a bad scrat*4 ,9 gr9d+ d[n ! section1 great c>e mu/ be tak5 to see t ! gr9d+ surface is kept p>allel to ! surface cem5t$ to ! glass4 ,! section is firmly press$ aga9/ ! lap by means ( two or ?ree f+]s1 dep5d+ on its size1 & uni=m pressure %\ld be ma9ta9$ ov] all p>ts4 ,! section %\ld be exam9$ frequ5tly1 & if x is notic$ t "o "p is ?ick] ?an ano!r1 place ! section on ! lap s t ! ?ick] "p is t[>ds ! p]iph]y1 & put a little m pressure ^u ?is "p4 ,gutt+ or groov+ ! copp] laps is prev5t$ by mov+ ! section f c5t] to p]iph]y & back1 at ! same "t giv+ to x a slight rot>y motion4 ,x is be/ to h ! lap revolve f "r to left 79 ! opposite way f ! h&s ( a wat*71 z1 hold+ ! section on ! "r side ( ! lap1 x is easi] to keep x 9 place by a pull+ motion r ?an by pu%+ x aga9/ ! motion ( ! lap4 ,9 ! f9al /ages ( gr9d+ & poli%+ great precaution mu/ be ex]cis$1 z "o or two turns too _m ( ! lap w (t5 te> away a l>ge "p ( ! v ?9 section4 ,! section %\ld be frequ5tly exam9$1 by transmitt$ light1 ) a small1 l[ p[] microscope1 a drop ( wat] or oil be+ put on ! section to r5d] x m transp>5t4 ,if ! section is ?ick & fa/5$ to ! plate-glass ) a good deal ( cem5t1 x w be f\nd conv5i5t1 aft] ! section has be5 gr\nd q ?91 to remove mo/ ( ?is cem5t f ar\nd its edges4 ,if ?is is n done1 x may delay ! f9al "w ( gr9d+ d[n4 ,a good rock section %\ld be made s ?9 t all ! transp>5t & transluc5t compon5t m9]als c be exam9$ & /udi$4 ,well made rock sections av]age 9 ?ickness f #j4jc to #j4je mm4 ,! la/ "p ( ! f9al gr9d+ & poli%+ c be done by ! h& on a gr\nd glass plate1 us+ ! f9e/ em]y du/ or r\ge & wat]4 ,fl\r em]y may also be us$ entirely = gr9d+1 & ! f9e/ em]y du/ = poli%+4 ,! f9] em]y makes bett] "w1 al?\gh x takes m "t1 & is mu* saf] = por\s or brittle sections1 z ! dang] ( te>+ away pieces ( ! section is avoid$4 ,9 ! case ( a por\s or decompos$ rock x is well be=e gr9d+ to boil ! section 9 ,canada balsam or o!r equival5t mat]ial s z to fill all ! pores & int]/ices1 ?us mak+ ! section m compact & less liable to *ip away4 ,sometimes x may ev5 be be/ be=e gr9d+ to m\nt ! section on its p]man5t glass slide1 s t :5 x has be5 gr\nd ?9 en\gh ! cov] c be put on )\t runn+ any risk 9 transf]r+ ! section4 ,! only objection is t ! glass slide may be a little scrat*$ by ! em]y4 ,m\nt+4 ,:5 ! section is suffici5tly ?9 & has a smoo? uni=m surface x is ready to be transf]r$ & m\nt$ ^u its p]man5t glass slide4 ,! glass plate1 :i* has held ! section dur+ ! gr9d+1 is g5tly heat$1 &1 z soon z ! cem5t beg9s to s(t51 ! section is v g5tly pu%$ (f into a %all[ cup or evaporat+ di% conta9+ turp5t9e or alcohol4 ,turp5t9e is conv5i5t = g5]al use1 because common alcohol 7on acc\nt ( ! wat] x conta9s7 unites ) ! %ellac to =m a k9d ( :ite pa/y sub/ance1 :i* is sometimes h>d to remove f ! section4 ,! section %\ld be c>efully clean$ 9 ! turp5t9e or alcohol ba? by means ( f9e camel's hair bru%es4 ,a section-lift]1 made f a piece ( broad1 flat wat*-spr+ fa/5$ to a small h&le1 is !n g5tly plac$ "u ! section1 :i* is lift$ out ( ! ba? 9 an incl9$ position s z to all[ ! liquid to dra9 (f4 ,if a drop /ill adh]es x c be remov$ by t\*+ x g5tly ) ! f+]4 ,! section is n[ plac$ 9 a tray1 ^u a piece ( :ite1 unglaz$ pap]1 s t x may ?or\ghly dry2 aft] :i* process x is transf]r$ to a glass slide1 &1 if necess>y1 its r\gh edges *ipp$ (f ) a knife4 ,if ! section is v l>ge1 & x is desir$ to m\nt x 9 two pieces1 x c easily be divid$ by hold+ "o half tightly betwe5 two glass slides & g5tly b5d+ ! o!r half ) ! f+]s4 ,! fracture w take place along ! edges ( ! glass slides4 ,a mixture ( gum dam> & b5zole is recomm5d$ = m\nt+1 ! claim be+ made t gum dam> does n turn yell[ ) age1 :]eas ,canada balsam may d s4 ,two solutions ( gum dam> & b5zole are us$4 ,"o v ?91 ab\t ! consi/5cy ( wat]1 ! o!r q ?ick1 ab\t ! consi/5cy ( mucilage4 ,bo? solutions are prep>$ by dissolv+ ! gum dam> 9 b5zole & filt]+ ?r\gh a l95 or silk rag4 ,if ! solution is too ?9 x c be ?ick5$ by plac+ ! bottle 9 a w>m place & all[+ ! excess ( b5zole to evaporate1 or if too ?ick1 m b5zole c be add$4 ,x is conv5i5t to keep ! solutions 9 %ort glass bottles1 ) wide necks & glass cov]s in/ead ( corks4 ,! solutions c be appli$ ) glass rods4 ,:5 ! section is all ready = its f9al m\nt+ x is c>efully c5t]$ ) a co>se ne$le on ! glass slide1#aca & a drop ( ! ?9 solution plac$ at ! edge ( ! section4 ,capill>y attraction w cause x to fl[ ov] ! glass slide "u ! section1 & :ile x is s(t ! section c be aga9 adju/$ 9 place4 ,! slide is !n plac$ 9 a cool1 du/ pro( place & all[$ to /& = ab\t twelve h\rs1 :5 ! cem5t w be set & ! section held firmly 9 place4 ,! upp] surface ( ! section is !n wa%$ ) a drop ( b5z9e1 & z mu* z may be necess>y ( ! ?ick m\nt+ solution plac$ ^u x ) a glass rod4 ,a cov] ( glass ( ! "r size is g5tly heat$ & plac$ 9 position ov] ! section4 ,c>e mu/ be tak5 n to h ! cov] too hot1 z x w\ld cause bubbles to =m 9 ! cem5t4 ,x is also be/ to re/ "o edge ( ! cov] on ! cem5t fir/1 & !n l[] x g5tly s z to prev5t air bubbles f be+ includ$4 ,! cov] is adju/$ & !n held firmly 9 position by means ( a m\nt+ clamp1 :i* presses out all sup]flu\s cem5t4 ,if a few small bubbles rema9 ne> ! edges !y may be let alone1 z !y w g5]ally "w out by !mselves 9 "t4 ,sometimes a l>ge bubble c be work$ out by local pressure ) ! f+] & g5tle heat+ ) a small iron rod4 ,if ! m\nt+ is unsatisfactory ! cov] %\ld be remov$ by heat+1 ! old cem5t wa%$ (f ) a camel's hair bru% & b5zole1 & a fre% cov] put on4 ,aft] ! cem5t has set1 ! clamp may be remov$1 b ! slide %\ld be left = #bd h\rs1 or long] if necess>y1 until ! cem5t is q h>d4 ,?is takes long] 9 hot ?an 9 cold wea!r4 ,! advantage ( us+ two solutions = m\nt+ is t ! section is firmly held 9 place on ! glass slide :ile ! cov] is be+ plac$ ov] x2 !re is ?us no slipp+ or slid+ ( ! section1 & :5 ! cov] is adju/$ 9 place ! "w is well f9i%$ & ! section /ill 9 ! c5tre ( ! slide4 ,canada balsam1 or balsam 9 xylol1 are also (t5 us$ = m\nt+4 ,! advantage ( ! latt] be+ its quick dry+ or 8sett+40 ,clean+ & ,f9i%+4 ,:5 ! cem5t has set ! sup]flu\s "p is s+$ by means ( a small hot iron rod4 ,c>e mu/ be tak5 n to use too l>ge a rod or to h x too hot1 z ! cem5t "u ! cov] might !n s(t5 & all[ ! cov] to slip or air bubbles to =m4 ,! s+e+ drives (f ! m volatile "p ( ! cem5t1 leav+ only a brittle residue1 :i* c be easily scrap$ (f ) a knife4 ,9 "s cases x may be necess>y to s+e & scrape twice4 ,! f9al clean+ is done ) a s(t rag & b5zole4 ,! slides are n[ ready to be m>k$1 ei!r ) a diamond p5cil or ) pa/$ labels4 ,conv5i5t ,app>atus = ,"w 9 a ,petrographical ,laboratory3 ,section lift]s made ( wat* spr+s1 ?ree sizes4 ,section hold]s or clamps = press+ out sup]flu\s cem5t4 ,ne$le po9ts m\nt$ 9 light h&les4 ,easy spr+ =ceps4 ,m\nt+ frame = c5t]+ section on glass slide4 ,small iron rod = s+e+4 ,small camel's hair bru%es4 ,cutt+ pli]s & =ceps4 ,set ( wood5 section trays4 ,glass /opp] bottles = b5zole1 b5z9e1 turp5t9e & alcohol4 ,op5 neck bottles1 ) cov]s = two m\nt+ liquids4 ,rotat+ m\nt+ /&4 ,small microscope = te/+ transp>5cy ( section4 ,glass rods4 ,small squ>es & rectangles ( plate-glass4 ,r\nd1 oval & squ>e cov]-glasses4 ,glass slides ) gr\nd edges4 ,,*apt] ,,vi4 ,,*emical ,,& ,,me*anical ,,te/s4 ,^! te/s may be necess>y to confirm an optical det]m9ation or to assi/ 9 ! diff]5tiation ( ! closely relat$ species ( a gr\p1 z = example1 ! diff]5t plagioclases 9 ! feldsp> gr\p4 ,!y may also be useful 9 ! case ( opaque sub/ances4 ,! ord9>y *emical me?ods employ$ 9 m9]al analyses are (t5 n applicable1 on acc\nt ( ! m9ute size ( ! m9]al "u inve/igation & ! lack ( %>pness 9 ! reactions4 ,^? me?ods#acb are to be pref]r$ :i* produce cry/allizations indep5d5t ( ! relative proportions ( ! mat]ials tak+ "p 9 ! reaction & also ( ! physical conditions invok$4 ,! te/s c be made ei!r on ! cry/al 9 a rock section or on ! isolat$ cry/al or fragm5t1 ! latt] me?od be+ pref]able :5 possible4 ,,*emical ,,te/s ,,made ,,on ,,cry/al ,,9 ,,section4 ,! "p ( ! section to be te/$ mu/ be prep>$ by ?or\gh wa%+ ) alcohol & b5zole to remove all traces ( balsam4 ,if ! section is cov]$1 ! cov]-glass c be cut across ) a diamond1 &1 aft] heat+1 ! desir$ portion remov$ ) a knife edge4 ,any portion ( a section c be isolat$ by surr\nd+ x ) a rim ( visc\s balsam or by putt+ on a new cov]-glass1 9 :i* a small hole has be5 made4#acc ,?is hole c be accurately adju/$ ov] ! special portion ( ! section & ! balsam remov$ by alcohol & b5zole4 ,! treatm5t ( rock sections ) ord9>y acids1 su* z hydro*loric1 may %[ ! pres5ce ( easily soluble m9]als#acd & c>bonates1 or di/+ui% silicates t are soluble ) jelly1 or produce et*$ figures on ! m9]als4 ,te/ = ,c>bonates4 ,:5 only pres5t 9 v m9ute gra9s ! te/ c be made z foll[s3 ,cov] ! rock section ) a drop ( wat] & a cov]-glass1 !n all[ a drop ( acid to sl[ly diffuse ?r\gh ! wat] film4 ,! glass cov] w prev5t ! escape ( ! gas bubbles#ace :i* w ?us surely be detect$4 ,if necess>y ! section c be w>m$ by heat+ ! project+ "p ( a suitable /&1 plac$ "u ! section on ! /age ( ! microscope4 ,te/ = ,gelat9iz+ ,silica4 ,cov] ! c>efully cleans$ section ) a little dilute acid 7commonly hydro*loric7 & let /&4 ,if too mu* acid is us$ ! resultant gelat9 w spread ov] ! :ole section & n appe> simply on ! gelat9iz+ silicate4 ,w>m ! section1 if necess>y1 & f9ally r9se (f ! rema9+ acid ?or\ghly ) wat]4 ,d n all[ ! action ( ! acid to cont9ue too long1 z x is desirable to obta9 only a v ?9 film ( gelat9\s silica ov] ! m9]als attack$1 s t ! optical te/s c /ill be made on ^! m9]als4 ,if aft] ! fir/ trial ! action has n be5 pron\nc$ en\gh1 ! te/ %\ld be repeat$4 ,! transp>5t film ( gelat9\s silica is made m visible by cov]+ ! section ) a drop ( wat]1 conta9+ a dilute solution ( fu*s9e4 ,aft] /&+ = "s "t ! section %\ld be wa%$1 :5 only ^? portions cov]$ by ! gelat9\s film w %[ ! color /a94 ,,et*$ ,,figures4#acf ,! results ( et*+ te/s c n be reg>d$ z v satisfactory 9 ! case ( sections ( m9]als 9 rock sections1 on acc\nt ( d\bt z to ! cry/allographic ori5tation ( ^! sections4 ,! symmetry ( ! et*$ figures dep5ds ess5tially on ! relation ( ! cry/al faces on :i* !y are obta9$ to ! planes ( symmetry4 ,! =ms ( ! et*$ figures diff] on ! same face ( a m9]al1 dep5d+ on ! reag5t us$1 b _! degree ( symmetry is indep5d5t ( ! reag5t or its degree ( conc5tration4 ,! %>pe/ figures are produc$ on cry/al & cleavage faces1 ! figures be+ less p]fect on artificially prep>$ faces1 ev5 :5 poli%$4 ,! et*+ te/s may1 h[ev]1 be tri$ to prove ! pres5ce ( tw9n+1 or to di/+ui% betwe5 m9]als ( simil> appe>ance b belong+ to diff]5t sy/ems4#acg ,v>i\s acids or alkalies are us$ to produce ! et*$ figures1 dep5d+ on ! m9]al to be te/$4 ,diff]5t factors influ5ce ! =mation ( good et*$ figures1 & t me?od mu/ be us$ :i* seems to give mo/ satisfactory results 9 ! giv5 case4 ,! action ( ! reag5t %\ld be suffici5tly pron\nc$ to develop cle>ly ! et*$ figures2 at ! same "t ! te/s mu/ be /opp$ be=e ! solv5t action has be5 too p[]ful4#ach ,aft] treatm5t = et*+ ! section %\ld be ?or\ghly wa%$ & exam9$ 9 "s fluid ( weak refraction 7) n l[] ?an t ( ! cry/al section71 su* z wat] or air4#aci ,! objective1 ( c\rse1 mu/ be focus$ on ! surface ( ! section4 ,,heat+ ,,sections ,,to ,,r$ness4#adj ,! "p ( ! section to be te/$ mu/ be remov$ f ! object glass1 c>efully cleans$ ( balsam1 & held on plat9um foil 9 ! oxidiz+ bl[pipe flame4 ,aft] ! te/ ! fragm5t us$ may be rem\nt$ 9 ,canada balsam = /udy4 ,z a result ( heat+3 ,colorless1 hydr\s m9]als 7zeolites & *lorites7 become cl\dy 9 appe>ance4 ,colorless silicates1 conta9+ protoxide ( iron 7z oliv9e1 or fa9tly color$ pyrox5e or amphibole71 become r$ or r$di%-br[n4 ,color$ m9]als may *ange _! color1 *loritic sub/ances becom+ br[n or black if heat$ en\gh4 ,hornbl5de always becomes pleo*roic1 & oliv9e sometimes becomes s4 ,memb]s ( ! sodalite gr\p may be turn$ blue1 if n already ( t color4 ,! di*roism 7yell[ to blue7 ( almo/ colorless iolite may be develop$4 ,c>bonace\s p>ticles may be di/+ui%$ f ! iron oxides by be+ consum$4#ada ,,me?ods ,,( ,,isolat+ ,,cry/als ,,or ,,m9]al ,,fragm5ts ,,= ,,te/+4#adb ,= ! application ( ^! me?ods ! rock or aggregate ( m9]als %\ld be r$uc$ to homog5e\s#adc gra9s ( uni=m size 7pref]ably cry/als or cleavages7 & n to p[d]4 ,?is is be/ done by p\nd+ 9 a metal mort>1 avoid+ all gr9d+ motion4 ,! sep>ations requir$ may be made by specific gravity solutions or magnetic me?ods1 alone or comb9$2 & 9 "s cases may be assi/$ by *emical action4 ,:5 o!r me?ods fail x may be necess>y to sep>ate s+le gra9s f a mixture by h&4 ,a groov$ piece ( plate-glass1 pass$ b5ea? ! objective ( ! microscope1 w be f\nd useful4 ,! desir$ gra9s 9 ?is groove c be pick$ out by means ( a piece ( f9e wax$ ?read or a f9e po9t$ /ick moi/5$ at ! end4 ,! h>dness ( ! homog5e\s gra9s may be obta9$ by press+ !m firmly into ! end ( a lead /amp or hold] & try+ ! effect ( scrat*+ ^u ! faces ( m9]als ( kn[n h>dness4 ,specific ,gravity ,sep>ation4#add ,accompli%$ by use ( fluids ( diff]5t specific gravity4 ,^! fluids c be made specifically light] by dilution1 & h5ce ! fragm5ts w fall to ! bottom 9 ord] ( decreas+ d5sity4 ,dilution ( ! heavy solutions to any specific gravity may be affect$ empirically until ! solution w j susp5d a fragm5t ( a m9]al hav+ ! desir$ specific gravity2 or ! exact specific gravity ( ! solution may be det]m9$ by ! ,we/phal balance4 ,! foll[+ indicators may be employ$ to det]m9e ! limits ( ! specific gravity ( ! solution to be us$ = sep>ation purposes 7,v4 ,golds*midt73 ,,no4 ,,"n4 ,,locality4 ,,sp4 ,,gr4 #a4 ,sulphur1 ,girg5ti1 #b4jgj #b4 ,hyalite1 ,walts*1 #b4afj #c4 ,opal1 ,s*eiba1 #b4bab #d4 ,natrolite1 ,brevig1 #b4bdf #e4 ,pit*/one1 ,meiss51 #b4bhd #f4 ,obsidian1 ,lip>i1 #b4cfb #g4 ,pe>lite1 ,hung>y1 #b4cig #h4 ,leucite1 ,vesuvius1 #b4dfe #i4 ,adul>ia1 ,/4 ,got?>d1 #b4egj #aj4 ,elolite1 ,brevig1 #b4fag #aa4 ,qu>tz1 ,middleville1 #b4fej #ab4 ,labradorite1 ,labrador1 #b4fhi #ac4 ,calcite1 ,rab5/e91 #b4gae #ad4 ,dolomite1 ,muhrw9kel1 #b4gcc #ae4 ,dolomite1 ,rauris1 #b4hfh #af4 ,prehnite1 ,kilpatrick1 #b4iaf #ag4 ,aragonite1 ,bil91 #b4icc #ah4 ,act9olite1 ,zill]?al1 #c4jbj #ai4 ,&alusite1 ,bod5mais1 #c4abe #bj4 ,apatite1 ,ehr5fri$]sdorf1 #c4ahj ,among ! heavy solutions employ$ may be m5tion$3 ,?\let's solution ( potassium-m]curic iodide 7,,ki3 ,hg,i#b #a3 #a4bd71 maximum specific gravity #c4aif4 ,kle9's solution ( cadmium borotung/ate 7#b;,h#b,o1 #b;,cd,o1 ,b#b,o#c1 #i,wo,o#c #af;,h#b,o71 maximum specific gravity #c4f4 ,^! two solutions c be mix$ ) wat] 9 any proportion )\t be+ decompos$4 ,solution ( b>ium m]curic iodide1 maximum specific gravity1 #c4ehh1 _c be dilut$ ) wat]4 ,me?yl5e iodide 7,,*#b;,i#b71 specific gravity #c4cbdc at #af ,c4 v>y+ ) ! temp]ature1 c be dilut$ ) b5zole b n ) wat]4 ,nitrates ( silv] & ?allium#ade 7,ag,n,o#c3 ,tl,n,o#c #a4a7 fuse at ab\t #ge ,c4 to a cle> mobile liquid ) specific gravity ov] #d4e4 ,c be mix$ :ile melt$ ) wat] 9 all proportions2 b _c be us$ = sep>ation ( sulphides1 z ^! nitrates are attack$ by !m4 ,possible *emical action betwe5 ! m9]als & heavy solutions mu/ n be ov]look$ 9 ?is me?od ( sep>ation4 ,! funnel-%ap$ app>atus = ^! sep>ations mu/ be s arrang$1 ) /op-cocks1 etc41 t ! heavi] mat]ial collect$ at ! bottom c be easily drawn (f or remov$ at any /age ( dilution4 ,^! sep>ations1 = v>i\s reasons1 are n always complete1 b ! be/ results are obta9$ :5 ! processes are repeat$ sev]al times4 ,electro-magnetic ,sep>ation4 ,all iron-be>+ m9]als may be sep>at$ f ^? free f iron by an electro-magnet4 ,! factors influ5c+ ! attraction ( a m9]al by an electro-magnet are n def9itely kn[n1 & d n seem to dep5d only on ! p]c5tage ( iron4 ,m9]als1 su* z amphibole1 pyrox5e1 epidote1 oliv9e & g>net 7conta9+ iron71 may (t5 be sep>at$ by an electro-magnet by regulat+ its magnetic int5sity4#adf ,sep>ation by ,*emical ,means4 ,v _m diff]5t me?ods may be us$1 dep5d+ on ! nature ( ! "w to be accompli%$2 b !y are g5]ally only reliable 9 ! h&s ( a good *emi/4 ,! mat]ial %\ld be 9 ! /ate ( f9e p[d]4 ,z an example may be m5tion$ ! treatm5t ) pure conc5trat$ ,h,fl1 by :i* ! m9]als ( a rock are attack$ 9 a c]ta9 sequ5ce1 ! feldsp>s & relat$ m9]als fir/1 !n ! qu>tz & f9ally ! f]ro-magnesium silicates1 su* z amphibole1 pyrox5e1 oliv9e1 etc4 ,,micro-,,*emical ,,reactions4 ,! fir/ requisite is to br+ ! sub/ance to be inve/igat$ into solution4 ,?is c be done 9 ! case ( non-silicates by ! ord9>y solv5ts1 :ile silicates c be decompos$ & inve/igat$ ei!r by ! me?ods ( ,bori*y or ,behr5s4 ,bo? me?ods re/ ^u ! recognition ( ! =ms1 etc41 ( artificially produc$ cry/als4 ,! size ( a fragm5t = te/+ may v>y1 accord+ to circum/ances1 f t ( a poppy se$ to a p9 head4 ,good results are record$ f fragm5ts ( n m ?an #j4b-j4g sq4 mm4 ,! sub/ance to be te/$ is plac$ on glass1 protect$ by a film ( balsam1 & cov]$ ) a sph]ical drop ( ! solv5t1#adg :i* %\ld be all[$ to act until all ! diff]5t elem5ts compos+ ! sample are 9 solution 79 ! case ( a v small fragm5t until x has all dissolv$74 ,transf] ! solution to ano!r protect$ object glass1 &1 aft] evaporation1 ! cry/allizations *>act]i/ic ( ! diff]5t elem5ts w be se54 ,if ! evaporation is too rapid & ! cry/allizations incomplete1 ! residue %\ld be r$issolv$ 9 wat]1 or a v dilute solution ( ! solv5t employ$1 transf]r$ to a fre% glass & all[$ to recry/allize4 ,bori*y's ,me?od4#adh 7,hydr(luosilicic ,acid47 ,?is me?od has ! advantage ( simplicity ( manipulation & relative di/9ctness 9 results2 b on ! o!r h& ^! results are only obta9$ aft] sev]al h\rs1 & ! temp]ature has an influ5ce on ! cry/all9e =ms obta9$4 ,x is well to make ! te/s 9 a temp]ature ( ab\t #ae ,c4 ,put a sph]ical drop ( pure hydr(luosilicic acid#adi on ! fragm5t & leave x = "s h\rs 9 damp air until ! action has be5 suffici5t1 !n transf] x to a dry air bell-glass & all[ evaporation & cry/allization to take place4 ,= ! microscopic exam9ation ! objective 7#bjj-cjj diams4 be/ = ^! obs]vations7 c be protect$ ) glyc]9e & a mica disc or ?9 cov]-glass1 or ! drop c be all evaporat$ & ! cry/als cov]$ ) liquid balsam & a cov]-glass4 ,cry/allizations ,obta9$ by ,bori*y's ,me?od4 ,potassium4 ,f hydr(luosilicic solutions1#aej isotropic1 colorless cry/als ( ,k#b,si,fl#f1 9 cubes1 octah$ra or comb9ations ( ^! =ms ) ! rhombic dodecah$ron4 ,app>5tly or?orhombic cry/als may =m f acid solutions & at a l[ temp]ature1 b if ^! cry/als are dissolv$ 9 hot wat] & recry/alliz$ !y w assume ! normal =ms4 ,plat9ic *loride w produce "u prop] conditions %>p1 yell[ octah$ra ( ,k#b,pt,cl#f4 ,illu/ration3 ,,fig4 #gh4--;,fluosilicate ( potassium4#aea ,illu/ration3 ,,fig4 #gi4--;,fluosilicate ( sodium4#aea ,sodium4 ,f hydr(luosilicic solutions1 colorless1 v weakly d\bly refract+1 hexagonal cry/als ( ,na#b,si,fl#f1 :i* are g5]ally long] ! high] ! p]c5tage ( sodium 9 ! solution4 ,?is te/ is v c]ta9 ev5 = small am\nts4 ,illu/ration3 ,,fig4 #hj4--;,fluosilicate ( calcium4#aea ,illu/ration3 ,,fig4 #ha4--;,fluosilicate ( magnesium4#aea ,calcium4 ,f hydr(luosilicic solutions1 monocl9ic cry/als ( ,ca,si,fl#f #b;,h#b,o ( v>i\s =ms1 g5]ally sp9dle-%ap$1 ) n v /rong d\ble refraction4 ,! cry/als h seldom /raight-edg$ b\nd>ies & are (t5 gr\p$ 9 rosettes4 ,! addition ( dilute ,h#b,,s#d decomposes ! cry/als1 recry/allization yield+ long prismatic cry/als ( gypsum 7di/9ction f /rontium74 ,treatm5t ) ,h,fl & dilute ,h#b,,s#d 79 excess71 produc+ on evaporation *>act]i/ic cry/als ( gypsum1 furni%es a v delicate te/ = small p]c5tages ( calcium4 ,magnesium4 ,f hydr(luosilicic solutions1 rhomboh$ral cry/als ( ,mg,si,fl#f #f;,h#b,o ) plane faces & %>p edges4 ,! cry/als are colorless & /rongly d\bly refract+ ) positive optical "*1 ,fig4 #ha4 ,! =mation ( /ruvite cry/als 7,,nh#d,mg,p,o#d #f;,h#b,o71 ( c(f9-l =ms1 is v *>act]i/ic & takes place f v dilute solutions 7r5d]$ alkal9e7 on ! addition ( a gra9 ( salt ( phosphorus or a drop ( sodium phosphate4 ,iron4 ,f hydr(luosilicic solutions1 cry/als ( ,fe,si,fl#f #f;,h#b,o1 :i* are isomorph\s ) ^? ( magnesium salts1 ) ! same optical *>act]s4 ,!y may be diff]5tiat$ by moi/5+ ) potassium f]rocyanide or ammonium sulphide1 9 ! fir/ case by turn+ blue1 9 ! second case black4 ,alum9ium4 ,f hydr(luosilicic solutions1 n satisfactory on acc\nt ( ! gelat9\s =mation4 ,:5 ! gelat9\s =mation is obta9$ by ! action ( hydr(luoric acid on an alum9\s silicate1 ! /a9+ te/ c be us$ to di/+ui% betwe5 f9e gra9s ( feldsp> & qu>tz or iolite & qu>tz4 ,behr5s' ,me?od4#aeb 7,hydr(luoric & ,sulphuric ,acids47 ,?is me?od dep5ds on common reactions t c be made rapidly1 b has ! disadvantage ( be+ r complicat$ & requir+ delicate manipulation4 ,! te/s are be/ made ^u ab\t mg4 ( p[d] ) ,h,fl 7pure & fum+74 ,z soon z ! fluorides beg9 to dry treat ) dilute ,h#b,,s#d & w>m until :ite fumes ( ,,s#c appe>4 ,9 ?is way ! ,h,fl & ,si,fl#d are driv5 (f & ! sulphates are left4 ,?is "p ( ! te/ c conv5i5tly be made on a piece ( plat9um foil4 ,add excess ( wat] & conc5trate4 ,transf] a drop to a clean object glass &1 :ile /ill liquid1 exam9e x ) ! microscope4 ,d n use a cov]-glass ov] ! drop4 ,cry/allizations ,obta9$ by ,behr5s' ,me?od4 ,potassium4 ,add a little plat9ic *loride :5 octah$ral cry/als ( ,k#b,pt,cl#f 7size 4#ah to 4#cj mm47 w appe>1 :i* are cle>1 bright yell[ 9 color ) /rong refraction4 ,illu/ration3 ,,fig4 #hb4--,potassium plat9ic *loride4#aec ,illu/ration3 ,,fig4 #hc4--,sulphate ( calcium 7gypsum74#aec ,sodium4 ,use sulphate ( c]ium & all[ a small am\nt ( ?is reag5t to act ?r\gh a capill>y pipette ^u a drop ( ! solution4 ,v small aggregates ( br[n cry/als 7size 4#jb mm47 ( ! d\ble sulphate ( c]ium & sodium are =m$1 :i* are cle>ly visible ) #fjj diams4 ,if potassium is pres5t ! d\ble sulphate ( t alkali w appe> 9 l>g]1 grayi% gra9s 7size 4#je to 4#jf mm474 ,an excess ( ,h#b,,s#d is to be avoid$4 ,calcium4 ,aft] a few m9utes little gypsum cry/als 7,ca,s,o#d #b;,h#b,o7 w appe>4 ,9 /rongly acid solutions ! ?9 acicul> cry/als w be gr\p$ 9 bu%es or />s2 9 neutral solutions ! cry/als w h ! normal %ape ( sel5ite cry/als or =m swall[-tail$ tw9s4 ,magnesium4 ,use salt ( phosphorus dissolv$ 9 wat] & all[ x to mix ) ! solution 7to :i* has be5 add$ ammonium *loride & ammonia7 ?r\gh a capill>y pipette4 ,f a solution conta9+ m ?an #e p] c5t4 ( magnesium are fir/ deposit$ ,x-%ap$ skeletons & rudim5t>y cry/als ( ,mg4,,nh#d4,,po#d #f;,h#b,o4 ,if ! solution is m dilute beautiful1 %>p1 hemimorphic cry/als 74#aj to 4#bj mm4 9 size7 ( ! or?orhombic sy/em w appe>4 ,^! cry/als (t5 resemble ! ro( ( a h\se4 ,! =mation ( ! cry/als is assi/$ by heat4 ,iron & manganese phosphates yield cry/als ( ! same type1 b ! iron is sep>at$ on ! addition ( ammonia4 ,alum9ium4 ,use *loride ( csium4 ,take a drop ( ! solution1 ) excess ( ,h#b,,s#d driv5 (f1 & t\* x ) a plat9um wire t has be5 dipp$ 9 ! melt$ *loride ( csium4 ,l>ge cry/als 74#dj-4ij mm4 9 size7 ( csium alum w =m1 :i* are octah$ral & cubo-octah$ral 9 %ape4 ,iron does n int]f]e1 z its cry/allization w\ld take place mu* m sl[ly4 ,! solution %\ld n be too conc5trat$4 ,illu/ration3 ,,fig4 #hd4--,magnesiumammonium phosphate4#aed ,illu/ration3 ,,fig4 #he4--;,csium alum4#aed ,special ,te/s4 ,di/9ction betwe5 haynite 7conta9s ,ca,s,o#d7 & noselite 7conta9s ,na#b,,s#d74 ,treat ) ,h,cl & on evaporation ! *>act]i/ic cry/als ( gypsum w be se5 if ! m9]al is haynite4 ,dilute acid %\ld be us$ & z l[ a temp]ature ma9ta9$ z possible1 o!rwise cry/als ( anhydrite w\ld =m in/ead ( gypsum4 ,recognition ( apatite by te/ = phosphorus4 ,treat ) a drop ( ammonium molybdate dissolv$ 9 ,,hno#c4 ,aft] complete action remove ! solution to a clean object glass1 :5 aft] slight w>m+ a l>ge numb] ( v small yell[ cry/als 7rhombic dodecah$ral 9 %ape7 w =m4 ,! te/ may be us$ to di/+ui% ?is m9]al f nephelite1 melilite & natrolite4 ,9 ! pres5ce ( soluble silica evaporate to r5d] x insoluble & treat aga9 ) ,,hno#c & ! reag5t4 ,o!r micro-*emical te/s are n m5tion$ = ! reason t 9 elaborate *emical inve/igations ( sections or isolat$ fragm5ts rec\rse %\ld be made to ! mo/ complete publications on ! subject4 ,,app5dix4 ,,brief ,,s*eme ,,( ,,classification ,,into ,,sy/ems ,,by ,,optical ,,det]m9ations4 ,,homog5e\s4 ,! :ole sub/ance %[s ! same optical "*1 except 9 ! case ( tw9 cry/als :5 ! diff]5t portions ( ! tw9 are affect$ diff]5tly4 ,isotropic ,all sections ( ! sub/ance rema9 d>k dur+ a complete rotation betwe5 cross$ nicols1 & no int]f]5ce figure is produc$ by conv]g5t light4 ,amorph\s ,abs5ce ( cry/all9e =m or cleavage4 ,isometric ,pres5ce ( cry/all9e =m or cleavage4 ,anisotropic4 ,sections g5]ally %[ "s int]f]5ce color & ext+ui% f\r times1 at #ij ap>t1 dur+ complete rotation4 ,uniaxial4 ,det]m9$ by "* ( int]f]5ce figures obta9$ by conv]g5t light f sections :i* rema9 d>k or ne>ly s dur+ complete rotation4 ,all sections %[ p>allel or symmetrical ext9ction4 ,tetragonal ,sections giv+ int]f]5ce figures are f\r- or eight-sid$1 or %[ rectangul> cleavage4 ,hexagonal ,sections giv+ int]f]5ce figures are ?ree-1 six- or n9e-sid$1 or %[ cleavage l9es int]sect+ at #fj4 ,biaxial ,det]m9$ by "* ( int]f]5ce figures obta9$ by conv]g5t light4 ,or?orhombic ,ext9ction is p>allel or symmetrical 9 all sections p>allel to 1 b & 4 ,color di/ribution is symmetrical to two l9es & to ! c5tral po9t1 see p4 #dh4 ,monocl9ic ,ext9ction is only p>allel or symmetrical 9 sections p>allel to ! or?o axis b2 all o!r sections %[ ext9ction angles4 ,color di/ribution is only symmetrical to "o l9e or to ! c5tral po9t1 see p4 #dh4 ,tricl9ic ,ext9ction angles 9 all sections1 al?\gh 9 "s m9]als ^! angles may be v small4 ,no symmetry 9 color di/ribution1 see p4 #dh4 ,,aggregate4 ,n homog5e\s1 b made up ( an aggregation ( individuals1 all ext+ui%+ at diff]5t times4 ,d\ble ,refraction 7maximum74#aee #j4bhg ,rutile #j4agi ,dolomite #j4agb ,calcite #j4ada ,titanite #j4jij ,titanite #j4jgb ,hornbl5de 7basaltic7 #j4jfb ,zircon #j4jeh ,biotite #j4jej ,talc #j4jej girite #j4jda ,muscovite #j4jcg ,epidote #j4jcf ,*rysolite 7,oliv9e7 #j4jcf ,scapolite 7,meionite7 #j4jcd ,t\rmal9e #j4jcd ,phlogopite #j4jcj ,allanite 7,or?ite7 #j4jbi ,diopside #j4jbg ,act9olite #j4jbg ,tremolite #j4jbd ,hornbl5de 7common7 #j4jbd ,diallage #j4jbd ,an?ophyllite #j4jbc ,augite #j4jba ,sillimanite 7,fibrolite7 #j4jah ,glaucophane #j4jag ,t\rmal9e 7preci\s7 #j4jaf ,cyanite 7,di/h5e7 #j4jac ,hyp]/h5e #j4jac ,scapolite 7,m>ialite7 #j4jac ,anor?ite #j4jab ,natrolite #j4jaa ,*lorite 7,cl9o*lore7 #j4jaa ,&alusite #j4jaa ,topaz #j4jaj ,/aurolite #j4jaj ,gypsum #j4jaj ,en/atite #j4jaj ,s]p5t9e #j4jji ,corundum #j4jji ,iolite 7,cordi]ite7 #j4jji ,qu>tz #j4jjh ,topaz #j4jjh ,kaol9 #j4jjh ,labradorite1 ,ab#a;,an#a #j4jjh ,oligoclase1 ,ab#d;,an#a #j4jjh ,albite #j4jjg ,or?oclase #j4jjg ,microcl9e #j4jjf ,vesuvianite #j4jje ,zoisite #j4jjd ,nephelite 7,elolite7 #j4jjc ,apatite #j4jjc ,melilite #j4jjb ,tridymite #j4jjb ,leucite #j4jjb ,allanite 7,or?ite7 #j4jja ,*lorite 7,p5n9ite7 #j4jja ,vesuvianite ,indices ( ,refraction 7mean74#aee #b4gab ,rutile #b4ch ,p](skite #b4jj ,sp9el 7,*rome7 #a4ifc ,titanite #a4ie ,zircon #a4ibj ,titanite #a4hef ,g>net 7,melanite7 #a4gib girite #a4gh ,allanite 7,or?ite7 #a4gh ,g>net 7,alm&ite7 #a4gff ,corundum #a4gea ,epidote #a4ge ,g>net 7,pyrope7 #a4gda ,/aurolite #a4gbc ,hyp]/h5e #a4gb ,sp9el #a4gbj ,zoisite #a4gbj ,cyanite 7,di/h5e7 #a4gai ,hornbl5de 7basaltic7 #a4gae ,vesuvianite #a4gaa ,augite #a4fii ,zoisite #a4fig ,diopside #a4fhh ,diallage #a4fge ,*rysolite 7,oliv9e7 #a4ffe ,en/atite #a4ffd ,sillimanite 7,fibrolite7 #a4fgd ,t\rmal9e #a4fdd ,an?ophyllite #a4fd ,hornbl5de 7common7 #a4fcg ,&alusite #a4fce ,apatite #a4fcb ,glaucophane #a4fcb ,topaz #a4fcj ,melilite #a4fcc ,t\rmal9e 7preci\s7 #a4fbb ,dolomite #a4fba ,act9olite #a4fba ,tremolite #a4fah ,biotite #a4fjh ,topaz #a4ehh ,*lorite 7,cl9o*lore7 #a4ehg ,muscovite #a4ehb ,anor?ite #a4egf ,*lorite 7,p5n9ite7 #a4egb ,talc #a4ehd ,scapolite 7,meionite7 #a4efd ,phlogopite #a4ef ,s]p5t9e #a4eei ,labradorite1 ,ab#a;,an#a #a4ee ,kaol9 #a4edg ,qu>tz #a4eea ,scapolite 7,m>ialite7 #a4fja ,calcite #a4eda ,oligoclase1 ,ab#d;,an#a #a4ed ,canada balsam #a4eci ,nephelite 7,elolite7 #a4eci ,iolite 7,cordi]ite7 #a4ece ,albite #a4ebe ,gypsum #a4ebe ,microcl9e #a4ebc ,or?oclase #a4eji ,leucite #a4ejc ,haynite #a4dhh ,analcite #a4dhc ,natrolite #a4dhc ,sodalite #a4dgg ,tridymite #a4df ,opal ,illu/ration3 ,diagram %[+ relation betwe5 /r5g? ( ,d\ble ,refraction1 ,int]f]5ce ,colors & ,?ickness ( ,section4#aef ,,ord] ,,( ,,consolidation ,,( ,,! ,,con/itu5t ,,m9]als ,,9 ,,plutonic ,,rocks4 8,!re is 9 plutonic rocks a normal ord] ( consolidation = ! sev]al con/itu5ts1 :i* holds good ) a high degree ( g5]ality4 ,x is 9 ! ma91 z po9t$ out by ,ros5bus*1 a law ( #8decreas+ basicity4' ,! ord] is briefly z foll[s3 8#a4 ,m9or accessories 7apatite1 zircon1 sph5e1 g>net1 etc47 & iron ores4 8#b4 ,f]ro-magnesian m9]als--oliv9e1 rhombic pyrox5es1 augite1 gir9e1 hornbl5de1 biotite1 muscovite4 8#c4 ,felspa?ic m9]als--plagioclase felsp>s 79 ord] f anor?ite to albite71 or?oclase 7& anor?oclase74 8#d4 ,qu>tz1 & f9ally microcl9e4 8,9 mo/ rocks su* m9]als z are pres5t foll[ ! above ord]4 ,! mo/ important exceptions are ! int]gr[? ( or?oclase & qu>tz & ! cry/allization ( qu>tz 9 advance ( or?oclase 9 "s acid rocks1 & ! r v>iable relations betwe5 gr\ps #b & #c 9 "s m basic rocks4 ,! ord] laid d[n applies 9 g5]al to p>allel int]gr[?s ( alli$ m9]als2 ?us :5 augite is int]gr[n ) gir9e or hornbl5de ! =m] m9]al =ms ! k]nel ( ! complex cry/al & ! latt] ! out] %ell2 :5 a plagioclase cry/al consi/s ( successive lay]s ( diff]5t compositions ! lay]s become progressively m acid f ! c5t] to ! m>g94 8,c]ta9 con/itu5ts hav+ v>iable relations are omitt$ f ! =ego+ li/4 ,?us nephel9e 7elolite7 & sodalite belong to gr\p #c1 b may cry/allize out ei!r be=e or aft] ! feldsp>40#aeg ,,optical ,,s*eme4 ,,introduction4 ,! s*eme is design$ to furni% ! /ud5t ) a practical me?od ( recogniz+ ! common m9]als 9 rock sections4 ,! arrangem5t foll[$ has be5 to gr\p m9]als hav+ g5]al optical *>act]s 9 common1 at ! same "t giv+ _! specific *>act]s s z to make x possible to di/+ui% "o f ano!r4 ,9 ea* rectangle ! m9]als are arrang$ 9 ord] ( _! indices ( refraction4 ,a tabulation ( ! m9]als1 ) a li/ ( optical *>act]s app5d$1 is ( aid to ! skill$ inve/igator1 b ( v little assi/ance to ! beg9n]4 ,! m common m9]als1 or ^? :i* are important petrographically1 are pr9t$ 9 heavy-fac$ type2 ! m9]als ( less importance 9 small capitals4 ,,abbreviations ,,& ,,conv5tions ,,us$4 ,a4 ,amorph\s4 ,i4 ,isometric sy/em4 ,t4 ,tetragonal sy/em4 ,o4 ,or?orhombic sy/em4 ,m4 ,monocl9ic sy/em4 ,tri4 ,tricl9ic sy/em4 ,h4 ,hexagonal sy/em4 ,m7,h74 ,monocl9ic1 ) hexagonal =m or *>act]s1 z 9 ! case ( biotite4 ,at "r angles to4 ,el4 ,elongation4 ,ex4 ,ext9ction4 ,ex4 ,p>allel ext9ction1 z :5 ! cry/als ext+ui% p>allel to cleavage l9es or cry/al edges4 ,ext9ction :i* is symmetrical to int]sect+ cleavage l9es is also includ$ "u ?is t]m4 ,! mean refractive indices are pr9t$ 9 heavy-fac$ type4 ,! t]m 8gra9s0 is us$ to describe n only m9]als :i* occur 9 typically granul> =m1 b also ^? :i* h co>s] allotriomorphic =m1 z elolite & sodalite 9 plutonic rocks1 su* z sy5ite1 etc4 ,,g5]al ,,rules ,,= ,,use ,,( ,,s*eme4 ,! division ( ! s*eme into two v]tical columns is bas$ on ! values ( ! mean refractive indices1 z det]m9$ by ! 8relief0 & appe>ance ( ! surface4 ,:5 ! refractive index is above #a4fj1 ! relief is fairly well to di/9ctly m>k$ & ! surface r\gh to v r\gh1 dep5d+ on ! value ( ! index4 ,mo/ ( ! rock-=m+ m9]als ) indices bel[ #a4fj %[ no relief & a smoo? surface1 except 9 ! case ( a few ( ! r>] m9]als 7mo/ly isometric71 :i* h v l[ indices & h5ce r\gh surface4 ,mi/akes may easily be made 9 ! case ( m9]als ne> ! limit2 b practice & ! use ( ! ,becke te/ %\ld soon make possible ! classification into ! two gr\ps sugge/$ by ! s*eme1 & ! app5d$ descriptions w help to *eck errors4 ,:5 an unkn[n m9]al lies adjac5t to "o t is kn[n1 use ! ,becke te/ = obta9+ ! relative refractive index ( ! unkn[n m9]al2 focus %>ply on ! l9e ( contact betwe5 ! kn[n & unkn[n m9]als1#aeh !n raise ! objective slightly & ! 8bright l9e0 w appe> on ! side ( ! m9]al hav+ ! high] index4 ,! me?od ( ,s*rd] van d] ,kolk may also be employ$1 see p4 #bb4 ,! horizontal divisions ( ! s*eme dep5d on ! relative /r5g? ( ! d\ble refraction bas$ on ! obs]v$ int]f]5ce colors4 ,^! colors to be ( use 9 classification mu/ be correctly recogniz$4 ,! l[] & middle colors ( ! #a ord]1 f blui%-gray ?r\gh :ite to yell[1 are easily kn[n4 ,! bright r$1 blue1 gre51 etc41 colors ( ! #a1 #b & #c ord]s c also be diff]5tiat$ )\t tr\ble f ! v high ord] colors 7#d & above71 :i* are ess5tially :ite 9 tone ) no decid$ color t9t4 ,:5 confusion arises1 ! exact ord] ( ! color c be det]m9$ by a qu>tz w$ge1 z giv5 on p4 #ce4 ,fur!rmore1 a undulation mica plate s]ves to quickly di/+ui% betwe5 ! #a ord] :ite & ! practically colorless1 high ord] t9t ( calcite1 titanite1 etc42 z aft] ! ins]tion ( ! te/-plate ! #a ord] :ite suff]s a m>k$ *ange 9 color1 :ile ! v high ord] 7practically :ite7 t9t %[s no appreciable *ange4 ,9 ! det]m9ation ( ^! int]f]5ce colors c>e mu/ be giv5 to consid]ations ( ori5tation & ?ickness4 ,! section mu/ give ! maximum int]f]5ce color ( all ! obta9able sections ( ! m9]al 9 ! rock section4 ,su* sections w be p>allel to ! axis 9 ! uniaxial m9]als & to ! axial plane 9 ! biaxial m9]als2 & w1 !re=e1 9 conv]g5t light nev] %[ ! em]g5ce ( an optic axis or bisectrix4 ,cry/al 8=m10 cleavage1 pleo*roism1 etc41 may at times aid 9 ! selection ( ^! sections4 ,! ?ickness ( ! section mu/ also be consid]$1 & x is well 9 all cases to pick out "s kn[n m9]al 9 ! section1 z qu>tz1 & note its maximum int]f]5ce color4 ,kn[+ h[ ?is v>ies f ! color giv5 by ! s*eme = a section #j4jc mm4#aei 9 ?ickness1 due all[ance c be made = a l v>iation 9 ! colors giv5 by ! o!r m9]als4 ,9 ! case ( m9]als ) /rong absorption ! int]f]5ce colors may n be noticeable on acc\nt ( ! absorption ( p>ts ( ! light4 ,"u ! subhead ( pleo*roism1 ! vibration direction ( ! ray ( a def9ite color is giv5 & n ! direction ( transmission ( t ray4 ,! int]f]5ce figures 9 conv]g5t light increase 9 cle>ness & di/9ctness ) ! /r5g? ( ! d\ble refraction4 ,9 uniaxial cry/als sections at "r angles to ! optic axis1 i4 e41 sections :i* rema9 d>k dur+ a revolution betwe5 cross$ nicols1 %[ ! be/ int]f]5ce figures4 ,9 biaxial cry/als ! mo/ *>act]i/ic int]f]5ce figures are %[n by sections at "r angles to ! acute bisectrix4 ,cry/al sections :i* are too small d n give v satisfactory int]f]5ce figures ) conv]g5t light4#afj ,any s*eme1 h[ev] design$1 makes a m or less arbitr>y classification ( ! m9]als1 & :5 9 d\bt x is always saf] to look = ! m9]al on bo? sides ( ! s*eme l9e4 ,! r>] m9]als are n includ$ 9 ?is s*eme1 s :5 ! det]m9ation ( a m9]al is unc]ta9 or n positive rec\rse %\ld be _h to m elaborate tables4 ,,index4 ,,m9]al ,,names ,,9 ,,heavy-,,fac$ ,,type4 ,abbreviations1 ix ,abnormal int]f]5ce colors1 #cj ,absorption1 #bf directions1 #bf t9ts1 #ag ,acmite1 #hc ,act9olite1 #hd ,acute bisectrix1 #e gir9e1 #hc gir9e-augite1 #hd ,aggregate /ructure1 #ch ,albite1 #ajc ,allanite1 #if ,allotriomorphic1 #ae ,alum9ium1 te/ =1 by ,bori*y's me?od1 #acg te/ =1 by ,behr5's me?od1 #aci ,amorph\s bodies1 #b ,amorph\s sub/ances1 te/ =1 #bf ,amphibole1 #hd ,analcite1 #ef ,analyz]1 #aj ,&alusite1 #gb ,anh$ron1 #ae ,anisotropic "*1 te/ =1 #bg ,anisotropic cry/als1 #b ,anomalies1 optical1 #bg ,anor?ite1 #ajc ,anor?oclase1 #aac ,an?ophyllite1 #hh ,antigorite1 #aad ,apatite1 #fh ,apatite1 recognition (1 by te/ = phosphorus1 #aci ,app>atus = petrographical laboratory1 #abg ,app5dix1 #ada ,arfv$sonite1 #hh ,augite1 #hj ,automorphic1 #ac ,axes ( ela/icity1 #d ,axial angle1 #e det]m9ation (1 #dg ,axial plane1 #e ,basaltic ,hornbl5de1 #he ,ba/ite1 #gg ,becke's me?od = det]m9+ relative values ( refractive indices1 #ai ,behr5's me?od4 7,hydr(luoric & sulphuric acids71 #acg ,b]tr& l5s1 #aa ,biaxial cry/als1 #d1 #e vibration directions 91 #d ,biaxial int]f]5ce figures1 #dc ,biotite1 #hi ,bisectrix1 acute1 #e obtuse1 #e ,bori*y's me?od4 7,hydr(luosilicic acid71 #ace ,brok5 or /ra9$ cry/als1 #ae ,bronzite1 #gf ,calcite1 #fe ,calcium1 te/ =1 by ,bori*y's me?od1 #acf te/ =1 by ,behr5's me?od1 #ach 8,cap0 nicol1 #aj ,c>bonace\s ,matt]1 #fa ,c>bonace\s p>ticles1 te/ =1 #acb ,c>bonates1 te/ =1 #acj ,cem5t1 #abb = m\nt+1 #abf ,cem5t+1 #aba ,c5t]+ /age1 #aj ,*alc$ony1 #fd ,*>act]s obs]v$ by1 conv]g5t light1 #dj cross$ nicols1 #bf reflect$ light1 #ac pol>iz$ light1 #be ,*>act]s ( opaque m9]als1 #ac transp>5t m9]als1 #ac ,*emical & me*anical te/s1 #abi ,*emical 7micro7 reactions1 #acd sep>ation1 #acd te/s on cry/al 9 section1 #abi ,*ia/olite1 #gb ,*lorite gr\p1 #ib ,*romite1 #eb ,*rysolite1 #gg ,*rysotile1 #aad ,circul> pol>ization1 #c ,classification into sy/ems by optical det]m9ations1 #ada ,clay1 #aae ,clean+ & f9i%+ sections1 #abf ,clean+ microscope1 #aa ,cleavage1 #bc ,cl9ozoisite1 #if ,color1 #ag diagram 7int]f]5ce71 #adc fr+es1 #dh ,cond5s+ l5s1 #i ,consolidation ( m9]als 9 plutonic rocks1 ord] (1 #add ,conv5tions1 ix ,conv]g5t light1 #dj *>act]s obs]v$ by1 #dj ,conv]g5t & p>allel light1 rsum ( uses (1 #di ,cordi]ite1 #gh ,corrod$ cry/als1 #ae ,corundum1 #fb ,cross$ nicols1 *>act]s obs]v$ by1 #bf ,cross$ tw9n+1 #cg ,cry/allites1 #af ,cry/allizations obta9$ by ,behr5's me?od1 #acg ,bori*y's me?od1 #ace ,cry/als b\nd$ by planes1 #ac ,cry/als )\t b\nd+ planes1 #ae ,cutt+1 #abj ,cutt+ & gr9d+ ma*9es1 #aag ,cyanite1 #aac ,dam\rite1 #ib ,delessite1 #id ,diagram1 %[+ relation betwe5 /r5g? ( d\ble refraction1 int]f]5ce colors & ?ickness ( section1 #adc ,diallage1 #hj ,diamond saws1 #aai ,di*roite1 #gh ,diopside1 #hj ,dipyre1 #ei ,directions ( ela/icity1 ix ,disp]sion1 #e1 #dh ,di/h5e1 #aac ,dolomite1 #fg ,d\ble image1 #b ,d\ble refraction1 #b1 #bg e/imation ( /r5g? (1 #cj /r5g? (1 measur$ by von ,f$][ mica w$ge1 #ce table 7maximum71 #adb ,effects produc$ by cry/als on transmitt$ light1 #b ,elolite1 #fi ,ela/icity1 axes (1 #d directions (1 ix ,electric motor = gr9d+ ma*9es1 #aag ,electro-magnetic sep>ation1 #acd ,em]y1 grades (1 = gr9d+1 #abd ,en/atite1 #ge ,epidote1 #id ,et*$ figures1 #acj ,ext9ction1 #ca angles1 #e1 #ca te/s =1 #cb wavy1 #ca ,extraord9>y ray1 #c ,eye-pieces1 #aa ,fa/] & sl[] rays1 te/ = vibration directions (1 #cc ,fayalite1 #gh ,feldsp> ,gr\p1 #ih ,feldspa?oids1 #fi ,fibrolite1 #gc ,f9i%+ & clean+ sections1 #abf ,focus+1 #aa ,=m ( cry/als1 #ac ,fracture1 #bd ,g>net1 #ec ,gelat9iz+ silica1 te/ =1 #acj ,glass slides1 #abe ,glaucophane1 #hh ,graphite1 #fa ,gravity 7specific7 sep>ation1 #acc ,gridiron tw9n+1 #cg ,gr9d+1 #abc ,gr9d+ & cutt+ ma*9es1 #aag app>atus = sections ) p>allel faces1 #aah plates or laps1 #aba ,gypsum1 #hj ,gypsum te/-plate1 #cc ,h>dness ( gra9s1 #acb ,hayne1 #ef ,haynite1 #ef ,haynite & noselite1 micro-*emical di/9ction betwe51 #aci ,heat+ sections to r$ness1 #aca ,heavy solutions1 #acc ,hematite1 #fa ,hexagonal cry/als1 #d ,high relief1 #ag ,hornbl5de1 #hd ,hyalosid]ite1 #gh ,hydr>gillite1 #aae ,hydr(luosilicic acid te/1 #ace ,hyp]/h5e1 #ge ,idiomorphic1 #ac ,idocrase1 #fj ,ilm5ite1 #fb ,inclusions1 #bd ,index ( refraction1 ix1 #ag by ,becke's me?od1 #ai by ,s*rd] van d] ,kolk's me?od1 #bb by ,sorby's me?od1 #ai ,indicators = specific gravity sep>ation1 #acc ,indices ( refraction 7mean71 table (1 #adb ,int]f]5ce color1 det]m9ation ( ord] (1 #ce ,int]f]5ce colors1 #bh ,int]f]5ce colors 7abnormal71 #cj ,int]f]5ce figures1 #dj biaxial1 #dc uniaxial1 #dj ,inve/igation ( microscopic & optical *>act]s ( m9]als1 #ac ,iolite1 #gh ,iron1 te/ =1 by ,bori*y's me?od1 #acg te/ =1 by ,behr5's me?od1 #aci ,isolat+ cry/als or m9]al fragm5ts = te/+1 #acb ,isometric cry/als1 #b ,isotropic "*1 #bf1 #dj cry/als1 #b ,kaol91 #aae ,labradorite1 #ajc ,laps = gr9d+1 #aba ,leucite1 #ed ,leucox5e1 #fb ,light1 ord9>y1 #a plane pol>iz$1 #a ,limonite1 #ea ,li?ia ,mica1 #ib ,ma*9es = cutt+ & gr9d+1 #aag ,magnesium1 te/ =1 by ,bori*y's me?od1 #acg te/ =1 by ,behr5's me?od1 #ach ,magnetic iron ore1 #eb ,magnetic pyrites1 #ea ,magnetite1 #eb ,measur+ /r5g? ( d\ble refraction by von ,f$][ mica w$ge1 #ce ,me*anical & *emical te/s1 #abi ,melilite1 #fa ,m5accanite1 #fb ,me?ods ( prep>+ sections1 #aag ,mica ,gr\p1 #hi ,mica plate 7qu>t] undulation71 #cc ,mica w$ge1 von ,f$][1 #ce ,micro-*emical reactions1 #acd ,microcl9e1 #ajb ,microlites1 #ag ,microscope 7petrographical71 #g ,microscopic & optical *>act]s ( m9]als1 #ea ,m9]als & ?ickness ( section1 det]m9$ by table & diagram1 #cf ,monocl9ic cry/als1 #d pr9cipal vibration directions 91 #e ,monocl9ic pyrox5es1 #hj ,m\nt+ sections1 #abd solutions1 #abe ,muscovite1 #hi ,natrolite1 #gi ,negative optical "*1 biaxial1 #df uniaxial1 #db ,nephel9e1 #fi ,nephelite1 #fi ,nicol prism1 #g ,nosean1 #ef ,noselite1 #ef ,noselite & haynite1 micro-*emical di/9ction betwe51 #aci ,nose-piece = microscope1 #aj ,objectives1 #aj ,oblique ext9ction1 #ca ,obtuse bisectrix1 #e ,oligoclase1 #ajc ,oliv9e1 #gg ,opal1 #ea ,opaque m9]als1 *>act]s (1 #ac ,optical1 anomalies1 #bg "*1 biaxial1 #df "*1 uniaxial1 #db classification into sy/ems1 #ada di/9ctions betwe5 or?orhombic1 monocl9ic & tricl9ic sections 7p]p5dicul> to bisectrices71 #dh1 #ada di/9ctions betwe5 tetragonal & hexagonal sections 7p]p5dicul> to optic axis71 #ada & microscopic *>act]s ( m9]als1 #ea pr9cipal section1 #c1 #d s*eme1 #ade ,optic axes1 #d ,optic axis1 #c ,optics = optical m9]alogy1 #a ,ord] ( consolidation ( m9]als 9 plutonic rocks1 #add ,ord] ( int]f]5ce color1 det]m9ation (1 #ce ,ord9>y light1 #a ray1 #c ,or?ite1 #if ,or?oclase1 #ih ,or?orhombic cry/als1 #d pr9cipal vibration directions 91 #d ,or?orhombic pyrox5es1 #ge ,p>allel & conv]g5t light1 rsum ( uses (1 #di ,p>allel ext9ction1 #ca ,p>allel face sections1 gr9d+ app>atus =1 #aai ,p>gasite1 #he ,p](skite1 #eg ,p]ovskite1 #eg ,petrographical app>atus1 #abg ,petrographical microscope1 #g ,ph5ocry/1 #ad ,phlogopite1 #hi ,picotite1 #ec ,pi$montite1 #ie ,plagioclases1 #ajc ,plane pol>iz$ light1 #a ,plates1 gr9d+1 #aba ,pleo*roic halos1 #ei ,pleo*roism1 #be te/ =1 #be ,pleona/e1 #ec ,pol>ization colors1 #bh ,pol>iz$ light1 *>act]s obs]v$ by1 #be plane1 #a ,pol>iz]1 #g te/ = vibration plane (1 #i ,poli%+ sections1 #abd ,polysyn!tic tw9n+1 #cg ,positive optical "*1 biaxial1 #df uniaxial1 #db ,potassium1 te/ =1 by ,bori*y's me?od1 #acf te/ =1 by ,behr5's me?od1 #ach ,prep>ation ( sections1 #aag ,pr9cipal section1 optical1 #c1 #d ,pr9cipal vibration directions1 #c1 #d ,prism1 nicol1 #g ,pseudomorphic /ructure1 #ci ,pyrite1 #ea ,pyrites1 #ea ,pyrox5es1 monocl9ic1 #hj ,pyrox5es1 or?orhombic1 #ge ,pyrrhotite1 #ea ,qu>t]-undulation mica plate1 #cc ,qu>tz1 #fc w$ge1 #cd ,reflect$ light1 *>act]s obs]v$ by1 #ac ,reflector1 #g ,refraction1 d\ble1 #b1 #bg ,refraction1 index (1 ix1 #ag ,refractive indices 7mean71 table (1 #adb ,relief1 #ag te/ =1 #ag1 #ah ,resorption bord]1 #ae ,rsum ( uses ( p>allel & conv]g5t light1 #di ,rotat+ /age ( microscope1 #aj ,rutile1 #eg ,sag5ite1 #eh ,sanid9e1 #ajb ,saussurite1 #if1 #aac ,saws1 #aai ,scapolite ,gr\p1 #ei ,s*eme ( classification into sy/ems by optical det]m9ations1 #ada ,s*eme1 optical1 #ade ,s*ill] /ructure1 #be ,s*rd] van d] ,kolk's me?od = det]m9+ refractive indices1 #bb ,sections1 me?ods ( prep>+1 #aag ?ickness ( rock1 #abd ,sel5ite plate1 #cc ,sep>ation1 by *emical means1 #acd by electro-magnet1 #acd by specific gravity1 #acc ,s]icite1 #ib ,s]p5t9e1 #aad ,%agre5$ surface1 #ag ,%orl1 #gj ,sillimanite1 #gc ,simple tw9n+1 #cg ,s+le image1 #b ,skeleton =ms1 #ag ,slides1 glass1 #abe ,sl[] & fa/] rays1 te/ = vibration directions (1 #cc ,sodalite1 #ef ,sodalite ,gr\p1 #ef ,sodium1 te/ =1 by ,bori*y's me?od1 #acf te/ =1 by ,behr5's me?od1 #ach ,sorby's me?od = det]m9+ index ( refraction1 #ai ,special micro-*emical te/s1 #aci ,specific gravity sep>ation1 indicators =1 #acc ,sphrulitic /ructure1 #ci ,sph5e1 #if ,sp9el1 #ec ,/age ( microscope1 rotat+1 #aj ,/aurolite1 #gd ,/ra9$ or brok5 cry/als1 #ae ,/r5g? ( d\ble refraction1 measure (1 #cj1 #ce ,/ructure1 #cg ,symmetrical ext9ction1 #ca ,sy/ems1 classification into1 by optical det]m9ations1 #ada ,table1 d\ble refraction1 #adb ,table1 indices ( refraction1 #adb ,talc1 #id ,te/ = vibration plane ( pol>iz]1 #i ,tetragonal cry/als1 #d ,?ickness ( rock sections1 #abd ,?ickness ( section & m9]als1 det]m9$ by table & diagram1 #cf ,titanite1 #if ,transmitt$ light1 *>act]s obs]v$ by1 #ac effect on cry/als1 #b ,transp>5t m9]als1 inve/igation ( *>act]s (1 #ac ,tremolite1 #hd ,tricl9ic cry/als1 #d pr9cipal vibration directions 91 #e ,tridymite1 #fe ,topaz1 #gd ,t\rmal9e1 #gj ,tw9n+1 #cg ,uniaxial cry/als1 vibration directions 91 #c ,uniaxial int]f]5ce figures1 #dj ,uralite1 #hh ,uralitization1 #hh ,uses ( p>allel & conv]g5t light1 #di van d] ,kolk's1 ,s*rd]1 me?od = det]m9+ refractive indices1 #bb ,vesuvianite1 #fj ,vibration direction1 #b directions ( fa/] & sl[] rays1 te/ =1 #cc directions1 pr9cipal1 #c1 #d plane ( nicol1 #i plane ( pol>iz]1 te/ =1 #i von ,f$][ mica w$ge1 #ce ,wavy ext9ction1 #af1 #ca ,w$ge1 mica1 #ce qu>tz1 #cd ,w]n]ite1 #ei ,x5omorphic1 #ae ,zeolites1 #gi ,zircon1 #eh ,zoisite1 #if & 1 #if ,zonal /ructure1 #ch ,,errata ,,& ,,add5da4 ,p4 #cc1 l9e #bc1 = beat read be at4 ,p4 #ff1 l9e #aj1 aft] appe>ance add 7sometimes call$ 8tw9kl+074 ,corrections = mean index ( refraction n3 p4 #fj1 l9e #a1 #a4eea to #a4ehd2 p4 #fb1 l9e #bi1 #a4gff2 p4 #ff1 l9e #c1 #a4fja2 p4 #fg1 l9e #bd1 #a4fbb2 p4 #ga1 l9e #aj1 #a4fcc to #a4fgd4 ,corrections = ,indices ( ,refraction 7mean7 9 ,table on p4 #adb3 ,corundum #a4gff2 ,t\rmal9e #a4fgd2 ,t\rmal9e 7preci\s7 #a4fcc2 ,dolomite #a4fbb2 ,scapolite 7,meionite7 #a4ehd2 ,scapolite 7,m>ialite7 #a4eea2 ,calcite #a4fja4 ,corrections = mean indices ( refraction 9 ,s*eme 7ins]t fold]73 ,scapolite #a4eea to #a4ehd2 ,calcite #a4fja & transf] to ,dolomite rectangle2 ,dolomite #a4fbb2 ,corundum #a4gff2 ,t\rmal9e #a4fcc to #a4fgd4 ----- ,footnote #a3 ,(t5 call$ a direction ( maximum ela/icity1 c be+ a direction ( m9imum ela/icity4 ,footnote #b3 ,ros5bus*'s ,microskopis*e ,physiographie1 p4 #aef4 ,footnote #c3 ,= a m complete discussion ( optics1 9 connection ) ,optical ,m9]alogy1 ! /ud5t is ref]r$ to ,a4 ,j4 ,moses' ,*>act]s ( ,cry/als1 p4 #he1 et seq42 ,moses' ,p>sons' ,m9]alogy1 ,cry/allography & ,bl[pipe ,analysis1 ,*ap4 ,,xvi41 #d? ,ed41 #aiji2 ,mi]s' ,m9]alogy1 #aijb2 ,l4 ,flet*]'s ,optical ,indicatrix1 etc41 #ahib2 ,gro?'s ,physikalis*e ,kry/allographie1 #c;d ,ed42 ,ros5bus*'s ,mikroskopis*e ,physiographie1 #d? ,ed4 & ,idd+s' ,rock ,m9]als1 #aiaa4 ,footnote #d3 ,! electromagnetic !ory ( light is n[ v g5]ally held1 b1 :atev] may be ! recurr5t *ange ( /ate to :i* light is really due1 ! pr9ciples ( wave motion furni% a satisfactory geometric description ( optical ph5om5a4 ,footnote #e3 ,^! sections are suppos$ to h plane p>allel faces1 su* be+ ! case 9 ord9>y practice1 & to be exam9$ ) p>allel p]p5dicul>ly incid5t light4 ,footnote #f3 ,x is int]e/+ to rememb] 9 ?is connection t 9 ! isometric sy/em !re is also ! greate/ possible symmetry ( 8=m40 ,footnote #g3 ,a4 ,j4 ,moses1 ,*>act]s ( ,cry/als1 pp4 #he-ig4 ,footnote #h3 ,= ?is bran* ( optical physics1 see ,a4 ,j4 ,moses1 ,*>act]s ( ,cry/als1 pp4 #ig-ajj4 ,footnote #i3 ,?is c be demon/rat$ by us+ a nicol & a plate ( calcite :i* %[s a d\ble image4 ,if ! nicol is held betwe5 ! calcite plate & ! obs]v]'s eye x c be s adju/$ t only "o image is se54 ,if n[ ! nicol is revolv$ #ij ! fir/ image w disappe> & ! o!r image alone w be se54 ,footnote #aj3 ,9 "s cases a peculi> =m ( d\ble refraction does take place p>allel to ?is direction1 z 9 ! circul> pol>ization ( qu>tz & c9nab>2 b 9 v ?9 sections ^! results are n notic$ & c be disreg>d$4 ,footnote #aa3 ,a4 ,j4 ,moses1 ,*>act]s ( ,cry/als1 pp4 #ih1 #ii4 ,footnote #ab3 ,! t]ms axes ( ela/icity are commonly us$ = ^! pr9cipal vibration directions 9 text-books on petrography4 ,footnote #ac3 ,in/ead ( & 1 = conv5i5ce 9 tables1 etc41 & are us$1 d5ot+ ! indices ( refraction ( ! rays trav]s+ ! cry/al ) greate/ & lea/ velocity respectively1 )\t reg>d z to :i* is ! ,o or ,e ray4 ,a good reason = ?is conv5tion is t ! symbol 7 7 is us$ to express 9 decimals ! relative /r5g? ( ! d\ble refraction ( a cry/al1 :e!r uniaxial or biaxial4 is always great] ?an 4 ,footnote #ad3 ,= mo/ cases 9 obs]vations ) :ite light ! 8optics axes0 may be reg>d$ z approximately fix$ 9 position4 ,footnote #ae3 ,(t5 spok5 ( z3 a1 ! axis ( maximum2 b1 ! axis ( int]m$iate1 & c1 ! axis ( m9imum ela/icity4 ,9 ! m rec5t ,am]ican text-books on ,optical ,m9]alogy by ,idd+s1 ,w9*ell & ,phillips a is d5ot$ by ,x1 b by ,y & c by ,z4 ,footnote #af3 ,= a %ort hi/orical sket* ( ! use ( ! microscope 9 connection ) ,petrology1 see ,g4 ,h4 ,william's pamphlet1 ,mod]n ,petrography 7,monographs ( ,education71 ,bo/on1 #ahhf4 ,= detail description & adju/m5ts1 see ,me?ods ( ,petrographic-,microscopic ,rese>*1 ,f4 ,e4 ,wright1 #aiaa1 pp4 #aa1 #fa4 ,footnote #ag3 ,= description ( ! ord9>y microscope1 eye-pieces1 objectives1 magnification1 etc41 see ,manipulation ( ! ,microscope1 by ,ed4 ,baus*4 ,footnote #ah3 ,text ,book ( ,m9]alogy1 by ,e4 ,s4 ,dana1 #ahih ,ed41 p4 #agf4 ,footnote #ai3 ,x is conv5i5t to assume t ! vibrations ( ! pol>iz$ light are tak+ place 9 ?is plane1 call$ ! 8plane ( vibration10 b all ! ph5om5a caus$ by pol>iz$ light c\ld be also expla9$ on ! assumption t ! vibrations 7 tak+ place at "r angles to ?is plane4 ,footnote #bj3 ,?is cond5s+ l5s mu/ be remov$ :5 v l[ p[] objectives are us$4 ,footnote #ba3 ,"s microscopes are provid$ ) adju/+ screws be>+ on ! frame hold+ ! objective1 :i* c !n be accurately c5t]$ to ! axis ( rotation ( ! /age4 ,footnote #bb3 ,9 ! ,seib]t microscope use objective ,no4 #jj = ! fir/ g5]al /udy ( a rock section1 ,no4 ,,ii = g5]al use & ,no4 ,v = obs]vations ) conv]g5t light4 ,9 ! ,fuess microscope use objective ,no4 #d = g5]al use & ,no4 #g = conv]g5t light te/s4 ,9 ! case ( an ,engli% microscope a #a to objective is us$ = g5]al purposes & a to = obs]vations ) conv]g5t light4 ,footnote #bc3 ,see pp4 #cc & #cd4 ,footnote #bd3 ,9 "s microscopes ! analyz] is 9 ! =m ( a 8cap0 nicol1 arrang$ to be fitt$ ov] ! top ( ! eye-piece1 & n introduc$ 9 ! microscope tube z %[n "h4 ,?is =m is n s conv5i5t1 z ! 8cap0 nicol mu/ be set by h& e "t x is desir$ to make obs]vations ) cross$ nicols4 ,b at ! same "t x avoids any possible refocus+ :i* may be necess>y :5 ! o!r type ( analyz] is introduc$ 9 ! tube4 ,footnote #be3 ,:5 accurate adju/m5ts are possible ( ! vibration planes ( ! nicols & ! cross-wires p>allel to ^! vibration planes1 ref]5ce %\ld be made to ,me?ods ( ,petrographic-,microscopic ,rese>*1 p4 #fa1 #aiaa1 ,fr$4 ,e4 ,wright4 ,footnote #bf3 ,9 ! ,seib]t microscope eye-piece ,no4 #j is us$ = mo/ purposes4 ,o!r eye-pieces1 ,nos4 #a & #b1 ) cross-wires1 are us$ = diff]5t degrees ( magnification1 & "o eye-piece1 ,no4 #c1 )\t cross-wires1 is provid$ to be us$ 9 connection ) an eye-piece micromet]4 ,footnote #bg3 ,) ! ,seib]t microscope1 ,fig4 #b1 ! ,no4 #j eye-piece & ! ,no4 ,,ii objective w prove mo/ satisfactory = ! foll[+ te/s4 ,) ! ,fuess microscope use ,no4 #d objective4 ,) an ,engli% microscope use an ord9>y eye-piece & a #a or objective4 ,footnote #bh3 ,tw9s may be recogniz$ j z 9 macroscopic specim5s1 & zonal /ructure notic$ if ! zones diff] 9 color4 ,:5 a colorless m9]al is surr\nd$ by o!r colorless m9]als1 ( ab\t ! same index ( refraction1 its outl9e is (t5 be/ br\ght out by obs]vation betwe5 cross$ nicols4 ,footnote #bi3 ,! t]m 8,anh$ron10 mean+ )\t planes1 has be5 sugge/$ by ,l4 ,v4 ,pirsson to describe 9 rocks ! cry/al fragm5ts :i* h no plane faces1 z1 = example1 ! augites ( augitic rocks4 ,sci5ce1 ,jan4 #aj1 #ahif1 p4 #di4 ,footnote #cj3 ,p>tial resorption & recry/allization may produce a bord] ( second>y m9]als1 surr\nd+ ! orig9al cry/al4 ,footnote #ca3 ,! surfaces ( all m9]als 9 sections are m or less r\gh1 b ?is r\ghness is only made visible :5 !re is a m>k$ diff]5ce betwe5 ! indices ( refraction ( ! m9]als1 & ! index ( refraction ( ! balsam 9 :i* ! m9]als are emb$d$4 ,! index ( refraction ( balsam is ab\t #a4ed1 s x is only :5 ! m9]al has a high] or l[] index ( refraction t its surface appe>s r\gh4 ,:5 int]nal /ructure is to be /udi$1 ! cry/al %\ld be surr\nd$ by a fluid ( ne>ly ! same index ( refraction z t ( ! cry/al1 & :5 ! ext]ior ( ! cry/al is to be /udi$1 !n a fluid %\ld be us$ ) a v diff]5t index ( refraction4 ,footnote #cb3 ,! ,seib]t microscope has a v conv5i5t & quick l[]+ adju/m5t1 by means ( ! lev] d1 = mak+ ?is te/4 ,= conv5i5ce ! l[] nicol & cond5s+ l5s are g5]ally left 9 place bel[ ! /age ( ! microscope1 z pol>iz$ light s]ves z well = ^! inve/igations z ord9>y light4 ,an additional advantage 9 ?is arrangem5t is t ! cond5s+ l5s is always ready = ! 8relief0 te/ & ! l[] nicol = ! pleo*roism te/2 b x mu/ be rememb]$ t ! pol>iz] or l[] nicol cuts out "o half ( ! light1 :i* comes to x f ! reflector1 & ?is loss is important :5 high p[] objectives are to be us$4 ,:5 v l[ p[] objectives are us$1 ! cond5s+ l5s mu/ be remov$4 ,footnote #cc3 ,mem4 de l',acad41 ,p>is1 #agfg-fh4 ,footnote #cd3 ,m94 ,mag41 ,vol4 ,i41 p4 #aic2 ,vol4 ,,ii41 p4 #a4 ,footnote #ce3 ,sitzungsb]i*te d] k4 k4 ,akad4 d] ,wiss41 ,wi51 #ahic1 ,i ,abt41 p4 #ceh4 ,translation by ,l4 ,mc,i4 ,luqu] 9 ,s*ool ( ,m9es ,qu>t]ly1 ,vol4 ,,xxiii41 ,jan41 #aijb1 ,no4 #b1 p4 #abg4 ,review by ,viola 9 ,m94 ,pet4 ,mitt41 ,vol4 #ad1 p4 #eed4 ,me?ods ( ,petrographic-,microscopic ,rese>*1 ,f4 ,e4 ,wright1 #aiaa1 p4 #ie4 ,footnote #cf3 ,mo/ ( ! petrographical microscopes c>ry ov] ! pol>iz] a convex l5s ! effect ( :i* is to wid5 ! illum9at+ cone & h5ce make less visible ?is ph5om5on4 ,footnote #cg3 ,9 ,seib]t /ud5t microscope1 ,no4 ,,ii a1 use next to smalle/ light-/op4 ,"s ( ! ,fuess microscopes are suppli$ ) an iris-bl5de = limit+ ! cone ( light4 ,footnote #ch3 ,9 ,seib]t microscope use ,no4 ,v1 n suffici5tly m>k$ results be+ obta9$ ) ,no4 ,,ii4 ,footnote #ci3 ,see ,viola's diagram1 ,m9n4 ,pet4 ,mitt41 ,vol4 ,,xiv41 p4 #eef4 ,footnote #dj3 ,seib]t1 ,no4 ,,ii4 ,fuess1 ,no4 #d4 ,footnote #da3 ,kurze ,anleitung zur mikrosk4 ,kry/allbe/immung1 ,wiesbad51 #ahih1 & ,tabell5 zur mikrosk4 ,be/immung1 etc41 ,wiesbad51 #aijj4 ,me?ods ( ,petrographic-,microscopic ,rese>*1 ,f4 ,e4 ,wright1 #aiaa1 p4 #ic4 ,?is me?od is p>ticul>ly favorable = ! accurate det]m9ation ( ! refractive indices ( small isolat$ fragm5ts or gra9s1 by us+ liquids ( kn[n indices4 ,9 ?is case a bright l9e appe>s on ! 8ne>0 edge & a d>k l9e on ! 8f>0 edge if ! gra9 has a high] index ?an ! liquid4 ,! rev]se occurs :5 ! index is l[] ?an ! liquid4 ,:5 ! index is ! same 7us+ :ite light7 ! 8f>0 edge is blue & ! 8ne>0 edge r$ & also ! cont\rs ab\t disappe>4 ,f4 ,krantz1 ( ,bonn1 furni%es a s]ies ( #ba liquids 9 small bottles1 ) indices f #a4ddg to #a4hc4 ,! indices ( a few conv5i5t liquids are3 wat]1 #a4cd2 alcohol1 #a4cf2 glyc]9e1 #a4da2 olive oil1 #a4dg2 nut oil1 #a4ej2 clove oil1 #a4ed2 anise$ oil1 #a4eh2 almond oil1 #a4fj2 cassia oil1 #a4fc2 monobromnap?al5e1 #a4fe2 me?yl5e iodide1 #a4ge4 ,footnote #db3 ,cry/als t h two good cleavages (t5 develop s t ! direction ( elongation is p>allel to ! int]section ( ! two cleavages1 :ile 9 ! case ( cry/als ) "o good cleavage ! t5d5cy seems to be t[>ds a tabul> habit p>allel to ! cleavage4 ,footnote #dc3 ,h>k]'s ,petrology = ,/ud5ts1 p4 #cjf4 ,footnote #dd3 ,! l[] nicol is g5]ally s adju/$ t its plane ( vibration is p>allel to ! nor? & s\? cross-wire 9 ! eye-piece4 ,?is adju/m5t c be te/$ by means ( a section ( biotite1 %[+ cleavage cracks4 ,:5 ! plane ( vibration ( ! pol>iz] is p>allel to ! ,n4 & ,s4 cross-wire 9 ! eye-piece1 ! biotite section becomes almo/ d>k :5 its cleavage cracks are p>allel to ! same cross-wire4 ,! upp] nicol1 or analyz]1 mu/1 ( c\rse1 be remov$ dur+ ?is te/4 ,?is me?od is m conv5i5t ?an tak+ ! nicol out ( its frame1 9 ord] to asc]ta9 its plane ( vibration 7! direction ( its %ort] diagonal74 ,footnote #de3 ,al?\gh ! 8absorption directions0 may n necess>ily co9cide ) ! pr9cipal vibration directions 9 ,monocl9ic & ,tricl9ic cry/als2 /ill = conv5i5ce ! absorption colors are usually giv5 = ! light rays vibrat+ p>allel to ^! pr9cipal vibration directions4 ,footnote #df3 ,9 ! ,fuess & ,seib]t microscopes ! analyz] or upp] nicol is s fitt$ t x slides 9 & out ( ! tube ( ! microscope ) its plane ( vibration always at "r angles to ! plane ( vibration ( ! pol>iz] or l[] nicol4 ,footnote #dg3 ,moses' ,*>act]s ( ,cry/als1 p4 #ajf4 ,moses & ,p>sons' ,m94 ,cry/4 & ,b4 ,p4 ,analysis1 p4 #afc4 ,footnote #dh3 ,idd+s' ,rock ,m9]als1 #aiaa1 p4 #agb4 ,footnote #di3 ,^! sections always conta9 ! pr9cipal vibration directions a & c4 ,footnote #ej3 ,me?ods ( ,petrographic-,microscopic ,rese>*1 ,f4 ,e4 ,wright1 #aiaa1 p4 #aja4 ,footnote #ea3 ,a *>t ( int]f]5ce colors c be obta9$ f ,baudry et ,cie1 ,p>is1 & is also publi%$ 9 ,les ,m9raux des ,ro*es1 by ,lvy & ,lacroix1 ,rock ,m9]als 7#aiaa71 by ,idd+s & 9 ,ros5bus*'s ,mikroskopis*e ,physiographie4 ,footnote #eb3 ,idd+s' ,rock ,m9]als1 #aiaa1 pp4 #ada1 #ahc4 ,footnote #ec3 ,me?ods ( ,petrographic-,microscopic ,rese>*1 ,f4 ,e4 ,wright1 #aiaa1 p4 #acb4 ,footnote #ed3 ,! undulation mica plate consi/s ( a ?9 cleavage ( mica on :i* is m>k$ c1 ! vibration direction ( ! sl[] ray1 :i* 9 mica is ! l9e jo9+ ! 8optic axes40 ,! ?ickness is su* t ! sl[] ray is wave-l5g? beh9d ! fa/] & ! int]f]5ce color is a blui%-gray4 ,! gypsum plate is a ?9 cleavage ( gypsum1 on :i* is usually m>k$ a1 ! vibration direction ( ! fa/] ray4 ,! *os5 ?ickness is su* z to produce ! r$ int]f]5ce color ( ! #a ord]4 ,footnote #ee3 ,! te/-plates are g5]ally introduc$ 9 ! slot k1 9 a microscope ( ! ,seib]t type1 or if a cap-nicol is us$ 9 a slot bel[ ?is4 ,9 case no provision is made by ! in/rum5t mak] = ^! te/-plates1 ! regul> analyz] is left out ( ! tube1 & a simple nicol prism is us$ z an analyz] & is held by ! obs]v] ov] ! eye-piece4 ,c>e mu/ be tak5 to h ! plane ( vibration ( ?is nicol at "r angles to t ( ! pol>iz]1 & to leave suffici5t room = ! introduction1 by h&1 ( ! te/-plate betwe5 ! eye-piece & ! nicol4 ,) c>e ! plates c be introduc$ ) suffici5t accuracy to make ! te/ practical4 ,footnote #ef3 ,a scale or *>t ( int]f]5ce colors1 or ! int]f]5ce color diagram1 %\ld be be=e ! obs]v] 9 ord] to avoid any mi/akes z to :e!r ! new color is high] or l[] 9 ! scale4 ,footnote #eg3 ,! qu>tz w$ge is cut s t "o ( its faces is exactly p>allel to ! axis 7h5ce also p>allel to ! c vibration direction7 :ile ! o!r face makes a v small angle ) x4 ,! direction c is m>k$ on ! w$ge4 ,footnote #eh3 ,describ$ "u next te/4 ,footnote #ei3 ,9 apply+ ?is rule c\nt ! #a ord] :ite z gre5 & ! #a ord] gray z blue4 ,footnote #fj3 ,a4 ,j4 ,moses1 ,trans4 ,n4 ,y4 ,acad4 ,sci41 ,vol4 ,,xvi41 p4 #ee1 ,jan41 #ahig4 ,footnote #fa3 ,e4 von ,f$][1 ,zeit4 f4 ,kry/41 etc41 ,vol4 ,,xxxv41 p4 #cdj1 #ahie4 ,footnote #fb3 ,aft] ! fir/ r\gh det]m9ation ( ! phase diff]5ce by ! mica w$ge1 ! m exact phase diff]5ce c be obta9$ by ! aid ( a good color *>t or diagram1 see end ( book4 ,footnote #fc3 ,x is n safe to use m9]als ne> ! edge ( ! section1 z ! ?icknesses are apt to be unequal4 ,footnote #fd3 ,see at end ( app5dix4 ,footnote #fe3 ,9 ?is way elim9ate1 s f> z possible1 ! effect ( ! ori5tation ( ! m9]al section4 ,footnote #ff3 ,! diff]5t m9]al sections are all suppos$ to h ! same ?ickness ?r\gh\t ! rock section4 ,footnote #fg3 ,h>k]'s ,petrology = ,/ud5ts1 #ahie1 p4 #ad4 ,footnote #fh3 ,idd+s' ,rock ,m9]als1 pp4 #aec1 #agc4 ,moses' ,*>act]s ( ,cry/als1 p4 #aae4 ,footnote #fi3 ,9 ! ,seib]t microscope use ,no4 ,v objective1 9 ,fuess microscope ,no4 #g objective1 & 9 ,engli% microscopes a or objective4 ,footnote #gj3 ,ea* conv]g5t ray w h its vibration direction ei!r 9 or at #ij to ! plane ?r\gh ! ray & ! optic axis4 ,h5ce all rays vibrat+ p>allel to ! vibration planes ( bo? nicols w be completely cut out4 ,z ! section is rotat$ new rays successively come into ^! positions1 s ! same effect is ma9ta9$4 ,footnote #ga3 ,9 ! ,seib]t microscope !re is a little slot k = ?is purpose j above ! objective4 ,footnote #gb3 ,! optical "* may also be det]m9$ 9 p>allel light by prov+ c771 a774 ,! optical "* ( ! pr9cipal zone or ! sign ( ! elongation is (t5 giv5 9 tables4 ,?is optical "* or sign is 77 :5 ! pr9cipal zone axis or ! direction ( elongation is p>allel to c & 77 :5 p>allel to a4 ,footnote #gc3 ,idd+s' ,rock ,m9]als1 #aiaa1 p4 #agb4 ,footnote #gd3 ,?is assumes ! optic axes = diff]5t colors to em]ge ab\t at ! same po9ts4 ,if !re is m>k$ 8disp]sion0 ! black b&s & hyp]bolas may be ra9b[-hu$1 z ) titanite4 ,footnote #ge3 ,! int]f]5ce figure1 p]p5dicul> to ! obtuse bisectrix1 w\ld be ( ! same type ) a l>g] axial angle4 ,ord9>ily ?is figure w\ld n come )9 ! limits ( ! field ( view ( ! microscope4 ,confusion may arise1 h[ev]1 b 9 a section p]p5dicul> to ! acute bisectrix ! cross dissolves m sl[ly into ! hyp]bolas ?an 9 ! case ( a section p]p5dicul> to ! obtuse bisectrix4 ,at times x may be necess>y to measure ! axial angle to be sure4 ,:51 h[ev]1 ! m9]al is kn[n1 ! section p]p5dicul> to ! acute bisectrix c be recogniz$1 because if ! m9]al is optically positive ! trace ( ! axial plane is p>allel to a & if negative p>allel to c4 ,footnote #gf3 ,= con/ruction ( qu>tz w$ge1 see p4 #cd4 ,footnote #gg3 ,! w$ge c be introduc$ 9 ei!r ( ! sev]al ways describ$ = ! introduction ( ! te/-plates on p4 #cc4 ,footnote #gh3 ,= me?ods ( measur+ ! axial angle1 see ,me?ods ( ,petrographic-,microscopic ,rese>*1 ,f4 ,e4 ,wright1 #aiaa1 p4 #adg4 ,= conv5i5ce 9 _m cases only #b;,e is record$1 z !n an indication is giv5 z to :e!r ! axial angle is visible ) an ord9>y microscope 7arrang$ = obs]vation ) conv]g5t light = int]f]5ce figures74 ,if #b;,e is v l>ge ! axial angle c only be obs]v$ by cov]+ ! section ) "s transp>5t1 /rongly refract+ fluid4 ,= ! ,seib]t microscope ) objective ,v ! limit = good results is ab\t #b;,e #ij-ajj4 ,footnote #gi3 ,= disp]sion1 etc41 see ,a4 ,j4 ,moses' ,*>act]s ( ,cry/als1 p4 #adj4 ,footnote #hj3 ,! sy/em ( cry/allization ( leucite has be5 ! subject ( mu* discussion4 ,its habit is isometric4 ,! cons5sus ( op9ion seems to be t leucite cry/allizes 9 ! isometric sy/em1 b t ! isometric molecul> arrangem5t1 at lea/ ( ! l>g] cry/als1 _c exi/ = ! temp]ature & pressure at ! e>?'s surface4 ,h5ce molecul> displacem5t takes place1 giv+ rise to a m or less complicat$ app>5t tw9n+1 & optical anomalies are notic$4 ,! isotropic "* returns if ! section is heat$ to #ejj ,c4 ,idd+s' ,rock ,m9]als1 p4 #bdi1 #aiaa4 ,footnote #ha3 ,c4 ,w4 ,knight1 ,canad4 ,rec4 ( ,sci41 ,,ix1 ,no4 #e4 #bfe4 ,footnote #hb3 ,! int]f]5ce colors ( all m9]als "h record$ are ^? giv5 by sections #j4jc mm4 9 ?ickness 7v ?9 sections74 ,footnote #hc3 ,%[n by ,mgge1 ,joly1 etc41 to be caus$ by radiations emanat+ f ,u1 ,?1 ,r1 etc4 ,idd+s' ,rock ,m9]als1 #aiaa1 p4 #ahi4 ,footnote #hd3 ,idd+s' ,rock ,m9]als1 #aiaa1 p4 #cib4 ,footnote #he3 ,see page #ca4 ,footnote #hf3 ,r4 ,d4 ,irv+1 ,am4 ,j\r4 ,sci41 ,june1 #ahhc4 ,footnote #hg3 ,granites ( ! c5tral ,alps1 :]e ! calcite cry/als are int]gr[n ) qu>tz4 ,footnote #hh3 ,! m9]als ,nephelite1 leucite1 sodalite 7haynite & noselite7 & melilite are (t5 gr\p$ toge!r "u ! "n 8feldspa?oides02 on acc\nt ( _! relation 9 rocks be+ equival5t to t ( ! feldsp>s4 ,footnote #hi3 ,ori5t$ 9 con=mity to ! int]gr[? ) augite1 etc41 7#jaj7 & 7#ajj7 are rev]s$4 ,footnote #ij3 ,= o!r alt]ation processes1 see ,idd+s' ,rock ,m9]als1 p4 #chj4 ,footnote #ia3 ,may be difficult to det]m9e 9 ! case ( prism zone sections1 %[+ l>ge ext9ction angles4 ,footnote #ib3 ,see p4 #hh4 ,footnote #ic3 ,idd+s' ,rock ,m9]als1 p4 #def1 #aiaa4 ,footnote #id3 ,dep5d+ on :e!r ! axial plane is p>allel or at "r angles to ! cl9o p9acoid 7#jaj7 7! plane ( symmetry71 we h micas ( ! second 7biotite7 or fir/ ord] 7muscovite74 ,footnote #ie3 ,! di/9ction betwe5 zoisite & 7ess5tially or?orhombic1 b may be composite tricl9ic tw9s7 & cl9ozoisite 7monocl9ic close to or?orhombic7 dep5ds on diff]5ces 9 position ( plane ( optic axes2 axial figures %[n by cleavage plates2 disp]sion2 anomal\s int]f]5ce colors2 etc4 ,see ,we9s*5k's ,die ,ge/e9bild5d5 ,m9]ali51 p4 #hc4 #aija4 ,footnote #if3 ,te/ n easily made on acc\nt ( ! v high ord] int]f]5ce colors1 result+ f ! /rong d\ble refraction4 ,footnote #ig3 ,see "u qu>tz1 p4 #fc4 ,footnote #ih3 ,idd+s' ,rock ,m9]als1 p4 #bjh1 #aiaa4 ,footnote #ii3 ,on acc\nt ( ! weak d\ble refraction ! int]f]5ce figures are n v %>p or well def9$ 9 ?9 sections4 ,9 mo/ cases only ! black hyp]bolas are se51 )\t any color$ curves4 ,footnote #ajj3 ,by heat+ feldsp> cry/als ! axial angle decreases to #j & !n increases 9 ! plane ( symmetry 7at "r angles to its =m] position74 ,on cool+ ! axial angle returns to its =m] position if ! temp]ature has n exce$$ #ejj ,c4 ,if ! temp]ature has be5 #fjj-ajjj ,c4 = "s "t ! axial angle w n return to its =m] position4 ,?is fact may give "s clew z to ! temp]ature at :i* ! feldsp> cry/als =m$4 ,footnote #aja3 ,?is *ange to kaol9 or clay 9 granite is call$ by ,dolomieu 8,la maladie du granit40 ,footnote #ajb3 ,see p4 #ca4 ,footnote #ajc3 ,hat*'s ,introduction to ! ,/udy ( ,petrology1 p4 #cc4 ,footnote #ajd3 ,j4 ,w4 ,judd1 ,geol4 ,mag4 #c1 ,vol4 ,,vi1 p4 #bdc1 #ahhi4 ,footnote #aje3 ,! plagioclases h r a complex composition2 b may be reg>d$ z =m+ a s]ies f ! composition ,na,al,si#c,o#h7;,ab7 to ! composition ,ca,al#b,si#b,o#h7;,an71 consi/+ = ! mo/ "p ( isomorph\s mixtures ( ^! types1 ) "s replacem5t by ,k,al,si#c,o#h4 ,! compositions ( only a few ( ! common plagioclases are giv5 above4 ,footnote #ajf3 ,! la?-%ap$ feldsp>s1 m\ld+ ! augite1 give to diabases ! s-call$ 8ophitic0 /ructure1 ,fig4 #ab4 ,! peculi>ity ( ?is /ructure is t ! feldsp>s cry/alliz$ be=e ! augite1 :i* is contr>y to ! usual ord] ( =mation4 ,footnote #ajg3 ,= ! positions ( ! optic axes1 bisectrices1 etc41 relative to ! cleavage plates ( ! diff]5t plagioclases1 see ,idd+s' ,rock ,m9]als1 p4 #bbb1 #aiaa4 ,footnote #ajh3 ,die ,ge/e9sbild5d5 ,m9]ali5 7) tables71 ,e4 ,we9s*5k1 ,freiburg1 #aija4 tude sur la ,dt]m9ation des ,feldspa?s dans les ,plaques ,m9ces1 ,mi*el ,lvy1 ,p>is1 #ahid2 & ,! ,det]m9ation ( ! ,feldsp>s1 ,n4 ,h4 ,w9*ell1 ,am4 ,geol41 ,vol4 ,,xxi1 ,no4 #a1 #ahih4 ,idd+s' ,rock ,m9]als1 ,wiley ,sons1 #aiaa4 tude sur la ,dt]m9ation des ,feldspa?s 7troisime fascicule71 ,mi*el ,lvy1 ,p>is1 #aijd4 ,footnote #aji3 ,glass models ( ! feldsp>s 7size #bj #aj cm47 by ,f4 ,krantz1 ,bonn4 ,diagrams1 %[+ optical ori5tation 9 ! plagioclases1 9 ,die ,ge/e9sbild5d5 ,m9]ali51 ,e4 ,we9s*5k1 p4 #acc1 #aija4 ,footnote #aaj3 ,= ?is me?od ( inve/igation little cleavage flakes or plates c (t5 be obta9$ f ! cru%$ m9]al1 b1 on acc\nt ( ,albite tw9n+1 plates are m apt to be obta9$ p>allel to ! tw9n+ plane ?an to ! be/ basal cleavage4 ,if a fragm5t ) only "o cleavage surface is obta9$1 x mu/ be cem5t$ to a glass by ?is surface & gr\nd d[n to a ?9 section ) p>allel sides4 ,footnote #aaa3 ,?is te/ is only possible :5 suitable sections ( ! giv5 feldsp> 9 ! rock section c be f\nd4 ,! me?od1 h[ev]1 c be us$ ) great accuracy ) ! aid ( "s =m ( app>atus = prop]ly ori5t+ ! section4 ,see 8,kle9's ,app>atus = ! ,ori5tation ( ,?9 ,sections10 ,sitzungsb]4 ,b]l94 ,akad41 #ahie1 #aaea2 7also 9 ,n4 ,y4 ,acad4 ,sci41 ,vol4 ,,xvi1 p4 #ea1 #ahig72 & ,von ,f$]ov's 8,univ]sal ,table10 ,zeit4 fr ,kry/1 etc41 ,vol4 ,,xxv41 p4 #cea4 ,footnote #aab3 ,9 ! det]m9ation ( feldsp> microlites x is well to rememb] ! foll[+ facts3 8,microcl9e is r>ely1 or nev]1 se5 9 ! condition ( microlites1 :ile ! associations ( labradorite & albite are s diff]5t t !re is little dang] ( conf\nd+ !m4 ,labradorite is ! commone/ product ( ! consolidation ( ! basic eruptives1 & albite almo/ inv>iably results f metamorphism1 frequ5tly f ! contact ( igne\s rocks on ! calc>e\s cla/ics40 ,n4 ,h4 ,w9*ell1 ,det]m9ation ( ! ,feldsp>s1 ,am4 ,geol41 ,vol4 ,,xxi1 ,no4 #a1 p4 #cc1 #ahih4 ,footnote #aac3 ,^! me?ods 7bo? #b & #c7 are (t5 n applicable on acc\nt ( ! t5d5cy ( ! cry/als 9 an effusive rock to p>allel ori5tation1 :i* may be s m>k$ t ! rock section does n %[ any favorable sections ( ! plagioclase4 ,footnote #aad3 ,^! ext9ction angles1 z well z ^? previ\sly giv51 are ^? ( only a few type feldsp>s ( def9ite composition4 ,z ! composition v>ies ?r\gh a long s]ies1 s ! ext9ction angle *anges1 "o be+ a function ( ! o!r4 ,= a complete li/ ( compositions & relat$ ext9ction angles1 see ,idd+s' ,rock ,m9]als & ,lvy ,lacroix's ,les ,m9raux des ,ro*es4 ,footnote #aae3 ,idd+s' ,rock ,m9]als1 p4 #bbh1 ,wiley ,sons1 #aiaa4 tude sur la ,dt]m9ation des ,feldspa?s 7troisime fascicule71 ,mi*el ,lvy1 ,p>is1 #aijd4 ,footnote #aaf3 ,9 qu>tz is ! refractive index ( ! ray ) vibration direction a t is ! direction ( vibration ( ! fa/] ray 7! ord9>y ray74 ,h5ce is direction a & c4 ,9 ! feldsp>s2 a1 c & b4 ,footnote #aag3 ,am4 ,j\r4 ,sci41 ,may1 #aijf4 ,?is me?od is specially useful 9 detect+ pres5ce ( or?oclase1 :5 plagioclase is ! dom9ant feldsp>4 ,footnote #aah3 ,^! te/s are only possible on pure & fre% mat]ial4 ,! specific gravity increases ) ! ,ca 7albite #b4fb1 anor?ite #b4ge74 ,footnote #aai3 ,9 cle> un/riat$ granules1 :i* may be di/+ui%$ f qu>tz by biaxial int]f]5ce figure 9 conv]g5t light4 ,footnote #abj3 ,! t5d5cy ( labradorite 9 gabbros to tw9n+1 aft] bo? ,albite & ,p]icl9e laws1 is to be not$4 ,footnote #aba3 ,w]veke's 7,n4 ,j4 ,b41 #ahhc1 ,,ii1 #ig7 !ory is t a tw9 lam9ation may be caus$ by ! =ces produc+ me*anical de=mations1 z movem5t 9 ! magma & m\nta9 mak+ pressure4 ,su* lamell are *>act]iz$ by ! fact t _! ext5t & c\rse seem to dep5d on fracture l9es 9 ! cry/al4 ,footnote #abb3 ,! d]ivation f pyrox5e & amphibole appe>s to be d\btful1 see ,we9s*5k's ,ge/e9sbild5d5 ,m9]ali51 #aija1 p4 #aba4 ,footnote #abc3 ,h>k]'s ,petrology = ,/ud5ts1 p4 #fc1 #ahie4 ,footnote #abd3 ,sections c be obta9$ f ,voight ,ho*gesang1 ,gtt+52 ,c4 ,m>*&1 rue ,c5si]1 #aft]1 ,p>is2 ,w4 ,h4 ,toml9son1 ,sw>?more1 ,pa41 & ,g4 ,d4 ,juli51 #c ,web/] ,t]race1 ,new ,ro*elle1 ,n4 ,y4 ,footnote #abe3 ,made by ,g4 ,d4 ,juli51 #c ,web/] ,t]race1 ,new ,ro*elle1 ,n4 ,y4 ,price3 ,p[] la!s 7complete71 #aej4jj up2 ,foot-treadle la!s1 #ij4jj up4 ,footnote #abf3 ,a ,crock]-,:eel] motor ( to ,h4 ,p4 w be l>ge en\gh = an ord9>y laboratory ma*9e4 ,footnote #abg3 ,made by ,voigt & ,ho*gesang1 ,gtt+54 ,price1 #ae4jj4 ,footnote #abh3 ,saws *>g$ ) diamond du/ c be obta9$ f ,eli%a ,t4 ,j5ks1 ,middleboro1 ,mass4 ,price 9 #aiaj1 #a4ce p] diametrical in*4 ,=eign saws #f & #h diam4 c be b\ght f ,g4 ,d4 ,juli51 ,new ,ro*elle1 ,n4 ,y4 ,footnote #abi3 ,s*ool ( ,m9es ,qu>t]ly1 ,vol4 ,,xi1 p4 #cb4 ,footnote #acj3 8,half a p\nd or less ( ord9>y %ellac is melt$ 9 a flat-bottom$ op5 vessel ov] a ,buns5 burn]4 ,!n an equal quantity ( ,v5ice turp5t9e is c>efully add$ "u con/ant /irr+4 ,! mass %\ld be all[$ to boil = ab\t t5 m9utes1 dur+ :i* ! /irr+ is cont9u$4 ,!n small quantities are p\r$ 9 sep>ate heaps on an iron plate or o!r cold surface & roll$ into /icks ab\t sev5 in*es long & half an in* ?ick40 ,footnote #aca3 ,squ>e or /&>d #bf #df mm4 glass slides are recomm5d$ in/ead ( ! oblong slides 7#a #c in*es71 :i* are v apt to project beyond ! edges ( ! /age & be /ruck by ! f+]s :ile rotat+ ! /age4 ,footnote #acb3 ,ref]5ce c be made to ! publications on ?is subject by3 ,bori*y1 ,behr5s 7,behr5's translation by ,judd71 ,hau%(]1 ,huysse1 ,klm5t1 ,/r5g1 ,rn>d1 etc4 ,footnote #acc3 ,9 case an acid is to be us$ :i* w\ld attack glass1 ! cov]-glass c be replac$ by a ?9 p]=at$ disk ( plat9um4 ,footnote #acd3 ,! bases 9 solution c be det]m9$ by diff]5t me?ods ( analysis1 = :i* ! /ud5t is ref]r$ to m elaborate works on ?is subject4 ,9 "s cases x may be v advantage\s to treat ! section ) acid1 to remove c]ta9 soluble con/itu5ts1 :5 o!r m9]als n di/9ctly se5 at fir/ may be made m app>5t4 ,footnote #ace3 ,! gas may be ,h#b,s f a soluble sulphide1 9 :i* case ! solution conta9+ ! bubbles w color filt] pap] moi/5$ ) lead wat]4 ,footnote #acf3 ,geol4 & ,nat4 ,hi/ory ,survey ( ,m9n41 ,,xix41 ,ann4 ,rept41 p4 #db2 also ,a4 ,j4 ,moses1 ,*>act]s ( ,cry/als1 p4 #adg4 ,footnote #acg3 ,! symmetry ( ! et*$ figures w\ld1 ( c\rse1 be relat$ to ! sy/em ( cry/allization4 ,footnote #ach3 ,a4 ,j4 ,moses1 ,*>act]s ( ,cry/als1 ,*ap4 ,,xvi4 ,footnote #aci3 ,:5 x is desir$ to pres]ve ! section & at ! same "t to /udy ! surface cov]$ ) a film ( air1 ! edges alone ( ! cov]-glass %\ld be cem5t$4 ,footnote #adj3 ,geol4 & ,nat4 ,hi/4 ,survey ( ,m9n41 ,,xix1 ,ann4 ,rept41 p4 #ej4 ,?9 sections ( #b-c sq4 mm4 area are ( a conv5i5t size1 & !y %\ld be subject$ to a r$ heat = 7#a7-c m9utes4 ,too long a cont9uance ( heat may r5d] ! sections too d>k or less5 _! transp>5cy or produce melt+4 ,footnote #ada3 ,?is te/ may v>y1 9 _m cases graphite n be+ consum$ ev5 aft] long heat+4 ,footnote #adb3 ,! isolation ( mat]ial = inve/igation is ( m int]e/ = ! li?ologi/ or *emi/ ?an = ! /ud5t ( optical m9]alogy2 !re=e only a v brief outl9e ( "s ( ! me?ods employ$ w be giv54 ,footnote #adc3 ,! gra9s pass+ ?r\gh diff]5t me%es are inve/igat$ microscopically to asc]ta9 :i* size gra9s are homog5e\s2 ! re/ ( ! sample %\ld !n be r$uc$ to gra9s ( ?is size4 ,footnote #add3 ,fur!r ref]5ce c be made to ,idd+s' ,rock ,m9]als1 pp4 #be & #ie1 #aiaa4 ,a conv5i5t =m ( app>atus is also describ$ 9 ,s*ool ( ,m9es ,qu>t]ly1 ,vol4 ,x41 p4 #bhd1 #ahhi4 ,footnote #ade3 ,s4 ,l4 ,p5field1 ,am4 ,j\r4 ,sci41 ,vol4 ,l41 p4 #ddf1 #ahie4 ,9 ?is article a conv5i5t =m ( sep>at+ app>atus is also describ$4 ,footnote #adf3 ,a conv5i5t li/ ( m9]als1 arrang$ 9 ! ord] 9 :i* !y w\ld be attract$ by increas+ ! =ce ( ! electro-magnet1 is giv5 9 ,we9s*5k's ,tabell54 ,footnote #adg3 ,= micro-*emical "w ! reag5ts %\ld be appli$ 9 v small drops1 :i* spread out on glass to discs #b mm4 9 diamet]4 ,= manipulat+ ! reag5ts use plat9um wires1 #j4e mm4 9 ?ickness4 ,footnote #adh3 ,elem5te e9] neu5 *emis*-mikroskopis*5 m9]al- und ,ge/e9s-analyse1 ,pragg1 #ahgg4 ,translation ( above by ,w9*ell 9 ,geol4 & ,nat4 ,hi/4 ,survey ( ,m9n41 ,vol4 ,,xix41 ,ann4 ,report1 #ahij4 ,footnote #adi3 ,! /r5g? ( ! solution %\ld be ab\t #c2 = if too weak _m m9]als d n give satisfactory results1 & if too /rong a v l>ge numb] ( fluosilicate cry/als are =m$ toge!r ) ! sep>ation ( mu* silica1 ?us mak+ x impossible to c>efully diff]5tiate ! cry/als ) a microscope4 ,footnote #aej3 ,z mo/ ( ! rock-=m+ m9]als t w\ld be inve/igat$ are silicates1 ! hydr(luosilicic solutions c also be obta9$ by treatm5t ) ,h,fl4 ,footnote #aea3 ,aft] ,lvy & ,lacroix4 ,footnote #aeb3 ,naturkunde1 ,am/]dam1 #b1 ,vol4 ,,xvii41 #ahha4 ,*emical ,news1 ,vol4 ,,lxiii41 ,no4 #afdg1 ,june #ahia1 et seq4 ,micro-*emical ,analysis1 ,behr5s 7,judd71 ,macmillan ,co41 ,london1 #ahid4 ,footnote #aec3 ,aft] ,lvy & ,lacroix4 ,footnote #aed3 ,aft] ,lvy & ,lacroix4 ,footnote #aee3 ,compil$ f ,we9s*5k's ,tables1 z revis$ 9 ,petrographic ,me?ods by ,we9s*5k-,cl>k1 #aiab4 ,footnote #aef3 ,pirsson & ,rob9son1 ,am4 ,j\r4 ,sci41 iv1 ,vol4 ,x1 ,oct41 #aijj4 ,footnote #aeg3 ,h>k]1 ,petrology = ,/ud5ts1 p4 #bh1 #ahie4 ,footnote #aeh3 ,h ! conv]g5t l5s or cond5s] l[]$ & ! analyz] out dur+ ?is te/4 ,footnote #aei3 ,! m9]als are gr\p$ accord+ to ! maximum int]f]5ce colors giv5 by sections ( ! ?ickness ( #j4jc mm4 ,footnote #afj3 ,9 ! case ( v small cry/als1 ! c5t]+ mu/ be accurate & a cov] ) a small hole 9 ! c5t]1 %\ld be plac$ ov] ! top ( ! tube4 ,9 ?is way ! eye is br\ght directly ov] ! axis ( ! microscope & figures c be obs]v$ f v m9ute cry/als4 ---------------------------------------- -------------------------------- ,,transcrib]',s ,,notes ,page ,*ang$ f ,*ang$ to #hj occurs z an alt]nation product occurs z an alt]ation product ( anhydrite4 ,gypsum is soluble ( anhydrite4 ,gypsum is soluble 9 hydro*loric 9 hydro*loric #acf long] ! high] ! p]c5tage long] ! high] ! p]c5tage ( calcium 9 ! solution ( sodium 9 ! solution ,typos fix$2 non-/&>d spell+ & dialect reta9$4 ,! au?or us$ ! old *emical symbol 7,fl7 = ,fluor9e4 ,correct$ ! ,errata ) ! exception ( ! la/ p>agraph ,corrections = mean indices ( refraction 9 ,s*eme 7ins]t fold]74 ,us$ numb]s = footnotes1 plac+ !m all at ! end ( ! la/ *apt]4 ,enclos$ italics font 9 und]scores4 ,enclos$ bold font 9 l[] half block4 ,! c>et 77 s]ves z a sup]script indicator1 applicable to individual *>act]s 7l #b;d7 & ev5 entire phrases 7l #a/74 ,subscripts are %[n us+ an und]score 77 ) curly braces 1 z 9 ,h#b,o4