,libraries47 ,,the ,,chemistry1 ,,properties ,,and ,,tests ,,of ,,precious ,,stones 99 99 99 99 99 ,,by ,,the ,,same ,,author ,,the ,,stolen ,,planet4 7#bnd edition47 #cs4 #f;d4 ,,through ,,the ,,sun ,,in ,,an ,,airship4 #fs4 ,,the ,,immortal ,,light4 7#bnd edition47 #fs4 ,c4 ,,griffin ,,and ,,co41 ,,ltd4 ,,the ,,autobiography ,,of ,a ,,picture4 7#bnd edition47 #cs4 #f;d4 ,,this ,,workaday ,,world4 7,in the ,press47 ,,henry ,j4 ,,drane4 ,,pepper',s ,,boy',s ,,playbook ,,of ,,science4 7,new edition47 ,now in ,press1 revised1 re-written and re-illustrated by ,,dr4 ,,john ,,mastin4 ,,george ,,routledge ,,and ,,sons1 ,,ltd4 ,,etc4 ,,etc4 99 99 99 99 99 ,,the ,,chemistry1 ,,properties ,,and ,,tests ,,of ,,precious ,,stones4 ,,by ,,john ,,mastin1 ,m4,a4 ,d4,,sc4 ,,ph4,d4 ,,litt4,d4 ,f4,s ,a4,,scot4 ,f4,l4,s4 ,f4,c4,s4 ,f4,r4,a4,s4 ,f4,r4,m4,s4 ,r4,b4,a4 ,author of ,parasites of ,insects1 ,the ,true ,analysis of ,milk1 ,plate-,culture and ,staining of ,amoebae1 etc41 etc4 ,london ,e4 ,f4 ,n4 ,,spon1 ,,limited1 #eg ,,haymarket ,,new ,,york ,,spon ,,chamberlain1 #abc ,,liberty ,,street #aiaa ,transcriber's note3 ,for ,text3 ,a word surrounded by a cedilla such as this signifies that the word is bolded in the text4 ,a word surrounded by underscores like this signifies the word is italics in the text4 ,the italic and bold markup for single italized letters or foreign abbreviations are deleted for easier reading4 ,for numbers and equations3 ,parentheses have been added to clarify fractions4 ,underscores before bracketed numbers in equations denote a subscript4 ,,contents ,,chapter ,,page ,i ,,introductory #a ,,ii ,,the ,,origin ,,of ,,precious ,,stones #g ,,iii ,,physical ,,properties--7,a7 ,,crystalline ,,structure #ac ,,iv 7,b7 ,,cleavage #ai ,v 7,c7 ,,light #bf ,,vi 7,d7 ,,colour #cb ,,vii 7,e7 ,,hardness #ci ,,viii 7,f7 ,,specific ,,gravity #de ,,ix 7,g7 ,,heat #eb ,x 7,h7 ,,magnetic ,,and ,,electric ,,influences #eg ,,xi ,,the ,,cutting ,,of ,,precious ,,stones #fb ,,xii ,,imitations1 ,,and ,,some ,,of ,,the ,,tests ,,of ,,precious ,,stones #gj ,,xiii ,,various ,,precious ,,stones #hj ,,xiv 7continued7 #hh ,,xv #ih ,,preface ,some little time ago certain ,london diamond merchants and wholesale dealers in precious stones made the suggestion to me to write a work on this section of mineralogy1 as there did not appear to be any giving exactly the information most needed4 ,finding there was a call for such a book ,i have written the present volume in order to meet this want1 and ,i trust that this handbook will prove useful1 not only to the expert and to those requiring certain technical information1 but also to the general public1 whose interest in this entrancing subject may be simply that of pleasure in the purchase1 possession1 or collection of precious stones1 or even in the mere examination of them through the plate-glass of a jeweller's window4 ,,john ,,mastin4 ,,totley ,,brook1 ,,near ,,sheffield4 ,june #aiaa4 ,,the ,,chemistry1 ,,properties ,,and ,,tests ,,of ,,precious ,,stones ,,chapter ,i4 ,,introductory4 ,what constitutes a precious stone is the question which1 at the onset1 rises in the mind1 and this question1 simple as it seems1 is one by no means easy to answer1 since what may be considered precious at one time1 may cease to be so at another4 ,there are1 however1 certain minerals which possess distinctive features in their qualities of hardness1 colour1 transparency1 refractability or double refractability to light-beams1 which qualities place them in an entirely different class to the minerals of a metallic nature4 ,these particular and non-metallic minerals1 therefore1 because of their comparative rarity1 rise pre-eminently above other minerals1 and become actually precious4 ,this is1 at the same time1 but a comparative term1 for it will readily be understood that in the case of a sudden flooding of the market with one class of stone1 even if it should be one hitherto rare and precious1 there would be an equally sudden drop in the intrinsic value of the jewel to such an extent as perhaps to wipe it out of the category of precious stones4 ,for instance1 rubies were discovered long before diamonds2 then when diamonds were found these were considered much more valuable till their abundance made them common1 and they became of little account4 ,rubies again asserted their position as chief of all precious stones in value1 and in many biblical references rubies are quoted as being the symbol of the very acme of wealth1 such as in ,proverbs1 chapter iii41 verses #ac and #ae1 where there are the passages1 happy is the man that findeth wisdom 444 she is more precious than rubies--and this1 notwithstanding the enormous quantity of them at that time obtained from the ruby mines of ,ophir and ,nubia1 which were then the chief sources of wealth4 ,it will also be remembered that ,josephus relates how1 at the fall of ,jerusalem1 the spoil of gold was so great that ,syria was inundated with it1 and the value of gold there quickly dropped to one-half2 other historians1 also1 speaking of this time1 record such a glut of gold1 silver1 and jewels in ,syria1 as made them of little value1 which state continued for some considerable period1 till the untold wealth became ruthlessly and wastefully scattered1 when the normal values slowly reasserted themselves4 ,amongst so many varieties of these precious minerals1 it cannot be otherwise than that there should be important differences in their various characteristics1 though for a stone to have the slightest claim to be classed as precious it must conform to several at least of the following requirements3--,it must withstand the action of light without deterioration of its beauty1 lustre1 or substance1 and it must be of sufficient hardness to retain its form1 purity and lustre under the actions of warmth1 reasonable wear1 and the dust which falls upon it during use2 it must not be subject to chemical change1 decomposition1 disintegration1 or other alteration of its substance under exposure to atmospheric air2 otherwise it is useless for all practical purposes of adornment or ornamentation4 ,there are certain other characteristics of these curious minerals which may be classified briefly1 thus3--,some stones owe their beauty to a wonderful play of colour or fire1 due to the action of light1 quite apart from the colour of the stone itself1 and of this series the opal may be taken as a type4 ,in others1 this splendid play of colour is altogether absent1 the colour being associated with the stone itself1 in its substance1 the charm lying entirely in the superb transparency1 the ruby being taken as an example of this class of stone4 ,others1 again1 have not only colour1 but transparency and lustre1 as in the coloured diamonds1 whilst the commoner well-known diamonds are extremely rich in transparency and lustre1 the play of light alone showing a considerable amount of brilliancy and beauty of colour1 though the stone itself is clear4 ,still others are opaque1 or semi-opaque1 or practically free from play of light and from lustre1 owing their value and beauty entirely to their richness of colour4 ,in all cases the value of the stone cannot be appreciated fully till the gem is separated from its matrix and polished1 and in some cases1 such as in that of the diamond1 cut in variously shaped facets1 on and amongst which the light rays have power to play2 other stones1 such as the opal1 turquoise and the like1 are cut or ground in flat1 dome-shaped1 or other form1 and then merely polished4 ,it frequently happens that only a small portion of even a large stone is of supreme value or purity1 the cutter often retaining as his perquisite the smaller pieces and waste4 ,these1 if too small for setting1 are ground into powder and used to cut and polish other stones4 ,broadly speaking1 the greatest claim which a stone can possess in order to be classed as precious is its rarity4 ,to this may be added public opinion1 which is led for better or worse by the fashion of the moment4 ,for if the comparatively common amethyst should chance to be made extraordinarily conspicuous by some society leader1 it would at once step from its humbler position as semi-precious1 and rise to the nobler classification of a truly precious stone1 by reason of the demand created for it1 which would1 in all probability1 absorb the available stock to rarity2 and this despite the more entrancing beauty of the now rarer stones4 ,the study of this section of mineralogy is one of intense interest1 and by understanding the nature1 environment1 chemical composition and the properties of the stones1 possibility of fraud is altogether precluded1 and there is induced in the mind--even of those with whom the study of precious stones has no part commercially--an intelligent interest in the sight or association of what might otherwise excite no more than a mere glance of admiration or curiosity4 ,there is scarcely any form of matter1 be it liquid1 solid1 or gaseous1 but has yielded or is now yielding up its secrets with more or less freedom to the scientist4 ,by his method of synthesis 7which is the scientific name for putting substances together in order to form new compounds out of their union7 or of analysis 7the decomposing of bodies so as to divide or separate them into substances of less complexity71 particularly the latter1 he slowly and surely breaks down the substances undergoing examination into their various constituents1 reducing these still further till no more reduction is possible1 and he arrives at their elements4 ,from their behaviour during the many and varied processes through which they have passed he finds out1 with unerring accuracy1 the exact proportions of their composition1 and1 in many cases1 the cause of their origin4 ,it may be thought that1 knowing all this1 it is strange that man does not himself manufacture these rare gems1 such as the diamond1 but so far he has only succeeded in making a few of microscopic size1 altogether useless except as scientific curiosities4 ,the manner in which these minute gems and spurious stones are manufactured1 and the methods by which they may readily be distinguished from real1 will be dealt with in due course4 ,the natural stones represent the slow chemical action of water1 decay1 and association with1 or near1 other chemical substances or elements1 combined with the action of millions of years of time1 and the unceasing enormous pressure during that time of thousands1 perhaps millions1 of tons of earth1 rock1 and the like1 subjected1 for a certain portion at least of that period1 to extremes of heat or cold1 all of which determine the nature of the gem4 ,so that only in the earth itself1 under strictly natural conditions1 can these rare substances be found at all in any workable size2 therefore they must be sought after assiduously1 with more or less speculative risk4 ,,chapter ,,ii4 ,,the ,,origin ,,of ,,precious ,,stones4 ,though the origin1 formation1 composition1 characteristics and tests of each stone will be examined in detail when dealing with the stones seriatim1 it is necessary to enquire into those particulars of origin which are common to all1 in order thoroughly to understand why they differ from other non-metallic and metallic minerals4 ,at the very commencement we are faced with a subject on which mineralogists and geologists are by no means in full agreement1 and there seems just ground for considerable divergence of opinion1 according to the line of argument taken4 ,it is a most remarkable fact that1 precious as are certain stones1 they do not 7with a few exceptions7 contain any of the rarer metals1 such as platinum1 gold1 etc41 or any of their compounds1 but are composed entirely of the common elements and their derivatives1 especially of those elements contained in the upper crust of the earth1 and this notwithstanding the fact that gems are often found deep down in the earth4 ,this is very significant1 and points to the conclusion that these stones were formed by the slow percolation of water from the surface through the deeper parts of the earth1 carrying with it1 in solution or suspension1 the chemical constituents of the earth's upper crust2 time and long-continued pressure1 combined with heat or cold1 or perhaps both in turn1 doing the rest1 as already mentioned4 ,the moisture falling in dew and rain becomes acidulated with carbonic acid1 ,,co#b 7carbon dioxide71 from the combustion and decay of organic matter1 vegetation1 and other sources1 and this moisture is capable of dissolving certain calcareous substances1 which it takes deep into the earth1 till the time comes when it enters perhaps a division-plane in some rock1 or some such cavity1 and is unable to get away4 ,the hollow becomes filled with water1 which is slowly more and more charged with the salts brought down1 till saturated2 then super-saturated1 so that the salts become precipitated1 or perhaps crystallised out1 maybe by the presence of more or other salts1 or by a change in temperature4 ,these crystals then become packed hard by further supplies and pressure1 till eventually1 after the lapse of ages1 a natural gem is found1 exactly filling the cavity1 and is a precious find in many cases4 ,if now we try to find its analogy in chemistry1 and for a moment consider the curious behaviour of some well-known salts1 under different conditions of temperature1 what is taking place underground ceases to be mysterious and becomes readily intelligible4 ,perhaps the best salt for the purpose1 and one easy to obtain for experiment1 is the sulphate of sodium--known also as ,glauber's ,salt4 ,it is in large1 colourless prisms1 which may soon be dissolved in about three parts of water1 so long as the water does not exceed #fj deg4 ,f41 and at this temperature a super-saturated solution may easily be made4 ,but if the water is heated the salt then becomes more and more insoluble as the temperature increases1 till it is completely insoluble4 ,if a super-saturated solution of this ,glauber's ,salt is made in a glass1 at ordinary atmospheric temperature1 and into this cold solution1 without heating1 is dropped a small crystal of the same salt1 there will be caused a rise in temperature1 and the whole will then crystallise out quite suddenly2 the water will be absorbed1 and the whole will solidify into a mass which exactly fits the inner contour of the vessel4 ,we have now formed what might be a precious stone1 and no doubt would be1 if continuous pressure could be applied to it for perhaps a few thousand years2 at any rate1 the formation of a natural jewel is not greatly different1 and after being subjected for a period1 extending to ages1 to the washings of moisture1 the contact of its containing bed 7its later matrix71 the action of the changes in the temperature of the earth in its vicinity1 it emerges by volcanic eruption1 earthquake1 landslip and the like1 or is discovered as a rare and valuable specimen of some simple compound of earth-crust and water1 as simple as ,glauber's ,salt1 or as the pure crystallized carbon4 ,it is also curious to note that in some cases the stones have not been caused by aqueous deposit in an already existing hollow1 but the aqueous infusion has acted on a portion of the rock on which it rested1 absorbing the rock1 and1 as it were1 replacing it by its own substance4 ,this is evidenced in cases where gems have been found encrusted on their matrix1 which latter was being slowly transformed to the character of the jewel encrusted1 or scabbed on it4 ,the character of the matrix is also in a great measure the cause of the variety of the stone1 for it is obvious that the same salt-charged aqueous solution which undergoes change in and on ironstone would result in an entirely different product from that resting on or embedded in silica4 ,following out the explanation of the aqueous solution1 in which the earth-crust constituents are secreted1 we find that the rarer and more precious metals do not generally enter into the composition of precious stones--which fact may advisedly be repeated4 ,it is1 of course1 to be expected that beryllium will be found in the emerald1 since it is under the species beryl1 and zirconium in zircon2 but such instances are the exception1 and we may well wonder at the actions of the infinite powers of nature1 when we reflect that the rarest1 costliest and most beautiful of all precious stones are the simplest in their constituents4 ,thus we find the diamond standing unique amongst all gems in being composed of one element only--carbon--being pure crystallised carbon2 a different form from graphite1 it is true1 but1 nevertheless1 pure carbon and nothing else4 ,therefore1 from its chemical1 as well as from its commercial aspect1 the diamond stands alone as the most important of gems4 ,the next in simplicity1 whilst being the most costly of all1 is the ruby1 and with this may be classed the blue sapphire1 seeing that their chemical constituents are exactly the same1 the difference being one of colour only4 ,these have two elements1 oxygen and aluminium1 which important constituents appear also in other stones1 but this example is sufficient to prove their simplicity of origin4 ,another unique stone is the turquoise1 in that it is the only rare gem essentially containing a great proportion of water1 which renders it easily liable to destruction1 as we shall see later4 ,it is a combination of alumina1 water1 and phosphoric acid1 and is also unique in being the only known valuable stone containing a phosphate4 ,turning to the silica series1 we again find a number of gems with two elements only1 silica--an important constituent of the earth's crust--and oxygen--an important constituent of atmospheric air4 ,in this group may be mentioned the opal1 amethyst1 agate1 rock-crystal1 and the like1 as the best known examples1 whilst oxygen appears also mostly in the form of oxides1 in chrysoberyl1 spinel1 and the like4 ,this silica group is extremely interesting1 for in it1 with the exception of the tourmaline and a few others1 the composition of the gems is very simple1 and we find in this group such stones as the chrysolite1 several varieties of topaz1 the garnet1 emerald1 etc41 etc4 ,malachite and similar stones are more ornamental than precious1 though they come in the category of precious stones4 ,these are the carbonate series1 containing much carbonic acid1 and1 as may be expected1 a considerable proportion of water in their composition1 which water can1 of course1 be dispelled by the application of heat1 but to the destruction of the stone4 ,from all this will be seen how strong is the theory of aqueous percolation1 for1 given time and pressure1 water charged with earth-crust constituents appears to be the origin of the formation of all precious stones2 and all the precious stones known have1 when analysed1 been found to be almost exclusively composed of upper-earth-crust constituents2 the other compounds which certain stones contain may1 in all cases1 be traced to their matrix1 or to their geological or mineralogical situation4 ,in contradistinction to this1 the essentially underground liquids1 with time and pressure1 form metallic minerals and mineralise the rocks1 instead of forming gems4 ,thus we see that in a different class of minerals--compounds of metals with the sulphates1 such as sulphuric acid and compounds2 also those containing the metallic sulphides2 in cases where the metalliferous ores or the metallic elements enter into composition with the halogens--bromine1 chlorine1 fluorine1 and iodine--in all these1 precious stones are comparatively common1 but the stones of these groups are invariably those used for decorative or ornamental purposes1 and true gems are entirely absent4 ,it would therefore appear that though metallic minerals1 as already mentioned1 are formed by the action of essentially underground chemically-charged water--combined with ages of time and long-continued pressure1 rocks and earth being transformed into metalliferous ores by the same means--precious stones 7or that portion of them ranking as jewels or gems7 must on the contrary be wholly1 or almost wholly1 composed of upper-earth-crust materials1 carried deep down by water1 and subjected to the action of the same time and pressure2 the simpler the compound1 the more perfect and important the result1 as seen in the diamond1 the ruby1 and the like4 ,,chapter ,,iii4 ,,physical ,,properties4 ,a--,,crystalline ,,structure4 ,before proceeding to the study of precious stones as individual gems1 certain physical properties common to all must be discussed1 in order to bring the gems into separate classes1 not only because of some chemical uniformity1 but also because of the unity which exists between their physical formation and properties4 ,the first consideration1 therefore1 may advisedly be that of their crystals1 since their crystalline structure forms a ready means for the classification of stones1 and indeed for that of a multitudinous variety of substances4 ,it is one of the many marvellous phenomena of nature that mineral1 as well as many vegetable and animal substances1 on entering into a state of solidity1 take upon themselves a definite form called a crystal4 ,these crystals build themselves round an axis or axes with wonderful regularity1 and it has been found1 speaking broadly1 that the same substance gives the same crystal1 no matter how its character may be altered by colour or other means4 ,even when mixed with other crystallisable substances1 the resulting crystals may partake of the two varieties and become a sort of composite1 yet to the physicist they are read like an open book1 and when separated by analysis they at once revert to their original form4 ,on this property the analyst depends largely for his results1 for in such matters as food adulteration1 etc41 the microscope unerringly reveals impurities by means of the crystals alone1 apart from other evidences4 ,it is most curious1 too1 to note that no matter how large a crystal may be1 when reduced even to small size it will be found that the crystals are still of the same shape4 ,if this process is taken still further1 and the substance is ground to the finest impalpable powder1 as fine as floating dust1 when placed under the microscope each speck1 though perhaps invisible to the naked eye1 will be seen a perfect crystal1 of the identical shape as that from which it came1 one so large maybe that its planes and angles might have been measured and defined by rule and compass4 ,this shows how impossible it is to alter the shape of a crystal4 ,we may dissolve it1 pour the solution into any shaped vessel or mould we desire1 recrystallise it and obtain a solid sphere1 triangle1 square1 or any other form2 it is also possible1 in many cases1 to squeeze the crystal by pressure into a tablet1 or any form we choose1 but in each case we have merely altered the arrangement of the crystals1 so as to produce a differently shaped mass1 the crystals themselves remaining individually as before4 ,such can be said to be one of the laws of crystals1 and as it is found that every substance has its own form of crystal1 a science1 or branch of mineralogy1 has arisen1 called crystallography1 and out of the conglomeration of confused forms there have been evolved certain rules of comparison by which all known crystals may be classed in certain groups4 ,this is not so laborious a matter as would appear1 for if we take a substance which crystallises in a cube we find it is possible to draw nine symmetrical planes1 these being called planes of symmetry1 the intersections of one or more of which planes being called axes of symmetry4 ,so that in the nine planes of symmetry of the cube we get three axes1 each running through to the opposite side of the cube4 ,one will be through the centre of a face to the opposite face2 a second will be through the centre of one edge diagonally2 the third will be found in a line running diagonally from one point to its opposite4 ,on turning the cube on these three axes--as1 for example1 a long needle running through a cube of soap--we shall find that four of the six identical faces of the cube are exposed to view during each revolution of the cube on the needle or axis4 ,these faces are not necessarily1 or always1 planes1 or flat1 strictly speaking1 but are often more or less curved1 according to the shape of the crystal1 taking certain characteristic forms1 such as the square1 various forms of triangles1 the rectangle1 etc41 and though the crystals may be a combination of several forms1 all the faces of any particular form are similar4 ,all the crystals at present known exhibit differences in their planes1 axes and lines of symmetry1 and on careful comparison many of them are found to have some features in common2 so that when they are sorted out it is seen that they are capable of being classified into thirty-three groups4 ,many of these groups are analogous1 so that on analysing them still further we find that all the known crystals may be classed in six separate systems according to their planes of symmetry1 and all stones of the same class1 no matter what their variety or complexity may be1 show forms of the same group4 ,beginning with the highest1 we have--7#a7 the cubic system1 with nine planes of symmetry2 7#b7 the hexagonal1 with seven planes2 7#c7 the tetragonal1 with five planes2 7#d7 the rhombic1 with three planes2 7#e7 the monoclinic1 with one plane2 7#f7 the triclinic1 with no plane of symmetry at all4 ,in the first1 the cubic--called also the isometric1 monometric1 or regular--there are1 as we have seen1 three axes1 all at right angles1 all of them being equal4 ,the second1 the hexagonal system--called also the rhombohedral--is different from the others in having four axes1 three of them equal and in one plane and all at #abj deg4 to each other2 the fourth axis is not always equal to these three4 ,it may be1 and often is1 longer or shorter4 ,it passes through the intersecting point of the three others1 and is perpendicular or at right angles to them4 ,the third of the six systems enumerated above1 the tetragonal--or the quadratic1 square prismatic1 dimetric1 or pyramidal--system has three axes like the cubic1 but1 in this case1 though they are all at right angles1 two only of them are equal1 the third1 consequently1 unequal4 ,the vertical or principal axis is often much longer or shorter in this group1 but the other two are always equal and lie in the horizontal plane1 at right angles to each other1 and at right angles to the vertical axis4 ,the fourth system1 the rhombic--or orthorhombic1 or prismatic1 or trimetric--has1 like the tetragonal1 three axes2 but in this case1 none of them are equal1 though the two lateral axes are at right angles to each other1 and to the vertical axis1 which may vary in length1 more so even than the other two4 ,the fifth1 the monoclinic--or clinorhombic1 monosymmetric1 or oblique--system1 has also three axes1 all of them unequal4 ,the two lateral axes are at right angles to each other1 but the principal or vertical axis1 which passes through the point of intersection of the two lateral axes1 is only at right angles to one of them4 ,in the sixth and last system1 the triclinic--or anorthic1 or asymmetric--the axes are again three1 but in this case1 none of them are equal and none at right angles4 ,it is difficult to explain these various systems without drawings1 and the foregoing may seem unnecessarily technical4 ,it is1 however1 essential that these particulars should be clearly stated in order thoroughly to understand how stones1 especially uncut stones1 are classified4 ,these various groups must also be referred to when dealing with the action of light and other matters1 for in one or other of them most stones are placed1 notwithstanding great differences in hue and character2 thus all stones exhibiting the same crystalline structure as the diamond are placed in the same group4 ,further1 when the methods of testing come to be dealt with1 it will be seen that these particulars of grouping form a certain means of testing stones and of distinguishing spurious from real4 ,for if a stone is offered as a real gem 7the true stone being known to lie in the highest or cubic system71 it follows that should examination prove the stone to be in the sixth system1 then1 no matter how coloured or cut1 no matter how perfect the imitation1 the test of its crystalline structure stamps it readily as false beyond all shadow of doubt--for as we have seen1 no human means have as yet been forthcoming by which the crystals can be changed in form1 only in arrangement1 for a diamond crystal is a diamond crystal1 be it in a large mass1 like the brightest and largest gem so far discovered--the great ,cullinan diamond--or the tiniest grain of microscopic diamond-dust1 and so on with all precious stones4 ,so that in future references1 to avoid repetition1 these groups will be referred to as group #a1 #b1 and so on1 as detailed here4 ,,chapter ,,iv4 ,,physical ,,properties4 ,b--,,cleavage4 ,by cleavage is meant the manner in which minerals separate or split off with regularity4 ,the difference between a break or fracture and a cleave1 is that the former may be anywhere throughout the substance of the broken body1 with an extremely remote chance of another fracture being identical in form1 whereas in the latter1 when a body is cleaved1 the fractured part is more readily severed1 and usually takes a similar if not an actually identical form in the divided surface of each piece severed4 ,thus we find a piece of wood may be broken or chopped when fractured across the grain1 no two fractured edges being alike2 but1 strictly speaking1 we only cleave wood when we split it with the grain1 or1 in scientific language1 along the line of cleavage1 and then we find many pieces with their divided surfaces identical4 ,so that when wood is broken1 or chopped1 we obtain pieces of any width or thickness1 with no manner of regularity of fracture1 but when cleaved1 we obtain strips which are often perfectly parallel1 that is1 of equal thickness throughout their whole length1 and of such uniformity of surface that it is difficult or even impossible to distinguish one strip from another4 ,advantage is taken of these lines of cleavage to procure long and extremely thin even strips from trees of the willow variety for such trades as basket-making4 ,the same effect is seen in house-coal1 which may easily be split the way of the grain 7on the lines of cleavage71 but is much more difficult and requires greater force to break across the grain4 ,rocks also show distinct lines of cleavage1 and are more readily split one way than another1 the line of cleavage or stratum of break being at any angle and not necessarily parallel to its bed4 ,a striking example of this is seen in slate1 which may be split in plates1 or laminae1 with great facility1 though this property is the result of the pressure to which the rock has been for ages subjected1 which has caused a change in the molecules1 rather than by cleavage as the term is strictly understood1 and as existing in minerals4 ,mica is also another example of laminated cleavage1 for given care1 and a thin1 fine knife to divide the plates1 this mineral may be cleaved to such remarkably thin sheets as to be unable to sustain the most delicate touch without shattering4 ,these are well-known examples of simple cleavage1 in one definite direction1 though in many instances there are several forms and directions of cleavage1 but even in these there is generally one part or line in and on which cleavage will take place much more readily than on the others1 these planes or lines also showing different properties and angular characters1 which1 no matter how much fractured1 always remain the same4 ,it is this cleavage which causes a crystal to reproduce itself exactly1 as explained in the last chapter1 showing its parent form1 shape and characteristics with microscopic perfection1 but more and more in miniature as its size is reduced4 ,this may clearly be seen by taking a very small quantity of such a substance as chlorate of potash4 ,if a crystal of this is examined under a magnifying glass till its crystalline form and structure are familiar1 and it is then placed in a test-tube and gently heated1 cleavage will at once be evident4 ,with a little crackling1 the chlorate splits itself into many crystals along its chief lines of cleavage 7called the cleavage planes71 every one of which crystals showing under the microscope the identical form and characteristics of the larger crystal from which it came4 ,the cleavage of minerals must1 therefore1 be considered as a part of their crystalline structure1 since this is caused by cleavage1 so that both cleavage and crystalline structure should be considered together4 ,thus we see that given an unchangeable crystal with cleavage planes evident1 it is possible easily to reproduce the same form over and over again by splitting1 whereas by simply breaking1 the form of the crystal would be lost2 just as a rhomb of ,iceland spar might be sawn or broken across the middle and its form lost1 although this would really be more apparent than real1 since it would be an alteration in the mass and not in the shape of each individual crystal4 ,and given further cleavage1 by time or a sudden breaking down1 even the mass1 as mass1 would eventually become split into smaller but perfect rhombs4 ,much skill is1 therefore1 required in cutting and fashioning a precious stone1 otherwise the gem may be ruined at the onset1 for it will only divide along its lines of cleavage1 and any mistake in deciding upon these1 would break1 not split the stone1 and destroy the beauty of its crystalline structure4 ,an example of this was specially seen in the great ,cullinan diamond1 the splitting of which was perhaps the most thrilling moment in the history of precious stones4,a ,the value of the enormous crystal was almost beyond computation1 but it had a flaw in the centre1 and in order to cut out this flaw it was necessary to divide the stone into two pieces4 ,the planes of cleavage were worked out1 the diamond was sawn a little1 when the operator1 acknowledged to be the greatest living expert1 inserted a knife in the saw-mark1 and with the second blow of a steel rod1 the marvellous stone parted precisely as intended1 cutting the flaw exactly in two1 leaving half of it on the outside of each divided portion4 ,the slightest miscalculation would have meant enormous loss1 if not ruin1 to the stone1 but the greatest feat the world has ever known in the splitting of a priceless diamond was accomplished successfully by this skilful expert in an ,amsterdam workroom in ,february1 #aijh4 ,some idea of the risk involved may be gathered from the fact that this stone1 the largest ever discovered1 in the rough weighed nearly #c1bed carats1 its value being almost anything one cared to state--incalculable4 ,footnote ,a3 ,the hammer and knife used in cutting the diamond1 the two largest pieces of which are now called ,the ,stars of ,africa1 together with a model of the great uncut stone1 are in the ,tower of ,london amongst the ,regalia4 ,these cleavage planes help considerably in the bringing of the stone to shape1 for in a broad sense1 a finished cut stone may be said to be in the form in which its cleavages bring it4 ,particularly is this seen in the diamond brilliant1 which plainly evidences the four cleavage planes4 ,these cleavage planes and their number are a simple means of identification of precious stones1 though those possessing distinct and ready cleavages are extremely liable to start or split on these planes by extremes of heat and cold1 accidental blows1 sudden shocks and the like4 ,in stones possessing certain crystalline structure1 the cleavage planes are the readiest1 often the only1 means of identification1 especially when the stones are chemically coloured to imitate a more valuable stone4 ,in such cases the cleavage of one stone is often of paramount importance in testing the cleavage of another1 as is seen in the perfection of the cleavage planes of calcite1 which is used in the polariscope4 ,it sometimes happens1 however1 that false conditions arise1 such as in substances which are of no form or shape1 and are in all respects and directions without regular structure and show no crystallisation even in the minutest particles2 these are called amorphous4 ,such a condition sometimes enters wholly or partially into the crystalline structure1 and the mineral loses its true form1 possessing instead the form of crystals1 but without a crystalline structure4 ,it is then called a pseudomorph1 which is a term applied to any mineral which1 instead of having the form it should possess1 shows the form of something which has altered its structure completely1 and then disappeared4 ,for instance3 very often1 in a certain cavity1 fluorspar has existed originally1 but1 through some chemical means1 has been slowly changed to quartz1 so that1 as crystals cannot be changed in shape1 we find quartz existing--undeniably quartz--yet possessing the crystals of fluorspar2 therefore the quartz becomes a pseudomorph1 the condition being an example of what is termed pseudomorphism4 ,the actual cause of this curious chemical change or substitution is not known with certainty1 but it is interesting to note the conditions in which such changes do occur4 ,it is found that in some cases1 the matrix of a certain shaped crystal may1 after the crystal is dissolved or taken away1 become filled by some other and foreign substance1 perhaps in liquid form2 or a crystalline substance may become coated or invested by another foreign substance1 which thus takes its shape2 or actual chemical change takes place by means of an incoming substance which slowly alters the original substance1 so that eventually each is false and both become pseudomorphs4 ,this curious change often takes place with precious stones1 as well as with other minerals1 and to such an extent that it sometimes becomes difficult to say what the stone ought really to be called4 ,pseudomorphs are1 however1 comparatively easy of isolation and detection1 being more or less rounded in their crystalline form1 instead of having sharp1 well-defined angles and edges2 their surfaces also are not good4 ,these stones are of little value1 except in the specially curious examples1 when they become rare more by reason of their curiosity than by their utility as gems4 ,some also show cleavage planes of two or more systems1 and others show a crystalline structure comprised of several systems4 ,thus calcspar is in the #bnd1 or hexagonal1 whilst aragonite is in the #dth1 the rhombic1 system1 yet both are the same substance1 viz43--carbonate of lime4 ,such a condition is called dimorphism2 those minerals which crystallise in three systems are said to be trimorphous4 ,those in a number of systems are polymorphous1 and of these sulphur may be taken as an example1 since it possesses thirty or more modifications of its crystalline structure1 though some authorities eliminate nearly all these1 and1 since it is most frequently in either the #dth 7rhombic7 or the #eth 7monoclinic7 systems1 consider it as an example of dimorphism1 rather than polymorphism4 ,these varieties of cleavage affect the character1 beauty and usefulness of the stone to a remarkable extent1 and at the same time form a means of ready and certain identification and classification4 ,,chapter ,v4 ,,physical ,,properties4 ,c--,,light4 ,probably the most important of the many important physical properties possessed by precious stones are those of light and its effects1 for to these all known gems owe their beauty1 if not actual fascination4 ,when light strikes a cut or polished stone1 one or more of the following effects are observed3--it may be transmitted through the stone1 diaphaneity1 as it is called2 it may produce single or double refraction1 or polarisation2 if reflected1 it may produce lustre or colour2 or it may produce phosphorescence2 so that light may be 7#a7 transmitted2 7#b7 reflected2 or produce 7#c7 phosphorescence4 7#a7 ,,transmission4--,in transmitted light we have1 as stated above1 single or double refraction1 polarisation1 and diaphaneity4 ,to the quality of refraction is due one of the chief charms of certain precious stones4 ,it is not necessary to explain here what refraction is1 for everyone will be familiar with the refractive property of a light-beam when passing through a medium denser than atmospheric air4 ,it will be quite sufficient to say that all the rays are not equal in refractive power in all substances1 so that the middle of the spectrum is generally selected as the mean for indexing purposes4 ,it will be seen that the stones in the #ast1 or cubic system1 show single refraction1 whereas those of all other systems show double refraction2 thus1 light1 in passing through their substance1 is deviated1 part of it going one way1 the other portion going in another direction--that is1 at a slightly different angle--so that this property alone will isolate readily all gems belonging to the #ast system4 ,a well-known simple experiment in physics shows this clearly4 ,a mark on a card or paper is viewed through a piece of double-refracting spar 7,iceland spar or clear calcite71 when the mark is doubled and two appear4 ,on rotating this rhomb of spar1 one of these marks is seen to revolve round the other1 which remains stationary1 the moving mark passing further from the centre in places4 ,when the spar is cut and used in a certain direction1 we see but one mark1 and such a position is called its optical axis4 ,polarisation is when certain crystals possessing double refraction have the power of changing light1 giving it the appearance of poles which have different properties1 and the polariscope is an instrument in which are placed pieces of double-refracting 7,iceland7 spar1 so that all light passing through will be polarised4 ,since only crystals possessing the property of double refraction show polarisation1 it follows that those of the #ast1 or cubic system--in which the diamond stands a prominent example--fail to become polarised1 so that when such a stone is placed in the polariscope and rotated1 it fails at every point to transmit light1 which a double-refracting gem allows to pass except when its optical axis is placed in the axis of the polariscope1 but this will be dealt with more fully when the methods of testing the stones come to be considered4 ,diaphaneity1 or the power of transmitting light3--some rather fine trade distinctions are drawn between the stones in this class1 technical distinctions made specially for purposes of classification1 thus3--a non-diaphanous stone is one which is quite opaque1 no light of any kind passing through its substance2 a diaphanous stone is one which is altogether transparent2 semi-diaphanous means one not altogether transparent1 and sometimes called sub-transparent4 ,a translucent stone is one in which1 though light passes through its substance1 sight is not possible through it2 whilst in a sub-translucent stone1 light passes through it1 but only in a small degree4 ,the second physical property of light is seen in those stones which owe their beauty or value to ,,reflection3 this again may be dependent on ,lustre1 or ,colour4 ,lustre4--,this is an important characteristic due to reflection1 and of which there are six varieties3--7alpha7 adamantine 7which some authorities1 experts and merchants subdivide as detailed below72 7beta7 pearly2 7gamma7 silky2 7delta7 resinous2 7epsilon7 vitreous2 7zeta7 metallic4 ,these may be described3-- 7alpha7 ,adamantine1 or the peculiar lustre of the diamond1 so called from the lustre of adamantine spar1 which is a form of corundum 7as is emery7 with a diamond-like lustre1 the hard powder of which is used in polishing diamonds4 ,it is almost pure anhydrous alumina 7,al#b,o#c7 and is1 roughly1 four times as heavy as water4 ,the lustre of this is the true adamantine1 or diamond1 brilliancy1 and the other and impure divisions of this particular lustre are3 splendent1 when objects are reflected perfectly1 but of a lower scale of perfection than the true adamantine standard1 which is absolutely flawless4 ,when still lower1 and the reflection1 though maybe fairly good1 is somewhat fuzzy1 or is confused or out of focus1 it is then merely shining2 when still less distinct1 and no trace of actual reflection is possible 7by which is meant that no object can be reproduced in any way to define it1 as it could be defined in the reflection from still water or the surface of a mirror1 even though imperfectly7 the stone is then said to glint or glisten4 ,when too low in the scale even to glisten1 merely showing a feeble lustre now and again as the light is reflected from its surface in points which vary with the angle of light1 the stone is then said to be glimmering4 ,below this1 the definitions of lustre do not go1 as such stones are said to be lustreless4 7beta7 ,pearly1 as its name implies1 is the lustre of a pearl4 7gamma7 ,silky1 possessing the sheen of silk1 hence its name4 7delta7 ,resinous1 also explanatory in its name2 amber and the like come in this variety4 7epsilon7 ,vitreous4 ,this also explains itself1 being of the lustre of glass1 quartz1 etc42 some experts subdividing this for greater defining accuracy into the sub-vitreous or lower type1 for all but perfect specimens4 7zeta7 ,metallic or ,sub-metallic4 ,the former when the lustre is perfect as in gold2 the latter when the stones possess the less true lustre of copper4 ,colour4--,colour is an effect entirely dependent upon light1 for in the total absence of light1 such as in black darkness1 objects are altogether invisible to the normal human eye4 ,in daylight1 also1 certain objects reflect so few vibrations of light1 or none1 that they appear grey1 black1 or jet-black2 whilst those which reflect all the rays of which light is composed1 and in the same number of vibrations1 appear white4 ,between these two extremes of none and all we find a wonderful play and variety of colour1 as some gems allow the red rays only to pass and therefore appear red2 others allow the blue rays only and these appear blue1 and so on1 through all the shades1 combinations and varieties of the colours of which light is composed1 as revealed by the prism4 ,but this is so important a matter that it demands a chapter to itself4 ,the third physical property of light1 ,,phosphorescence1 is the property possessed by certain gems and minerals of becoming phosphorescent on being rubbed1 or on having their temperature raised by this or other means4 ,it is difficult to say exactly whether this is due to the heat1 the friction1 or to electricity4 ,perhaps two or all of these may be the cause1 for electricity is developed in some gems--such as the topaz--by heat1 and heat by electricity1 and phosphorescence developed by both4 ,for example1 if we rub together some pulverised fluorspar in the dark1 or raise its temperature by the direct application of heat1 such as from a hot or warm iron1 or a heated wire1 we at once obtain excellent phosphorescence4 ,common quartz1 rubbed against a second piece of the same quartz in the dark1 becomes highly phosphorescent4 ,certain gems1 also1 when merely exposed to light--sunlight for preference--then taken into a darkened room1 will glow for a short time4 ,the diamond is one of the best examples of this kind of phosphorescence1 for if exposed to sunlight for a while1 then covered and rapidly taken into black darkness1 it will emit a curious phosphorescent glow for from one to ten seconds2 the purer the stone1 the longer1 clearer and brighter the result4 ,,chapter ,,vi4 ,,physical ,,properties4 ,d--,,colour4 ,colour is one of the most wonderful effects in nature4 ,it is an attribute of light and is not a part of the object which appears to be coloured2 though all objects1 by their chemical or physical composition1 determine the number and variety of vibrations passed on or returned to the eye1 thus fixing their own individual colours4 ,we have also seen that if an equal light-beam becomes obstructed in its passage by some substance which is denser than atmospheric air1 it will become altered in its direction by refraction or reflection1 and polarised1 each side or pole having different properties4 ,polarised light cannot be made again to pass in a certain direction through the crystal which has polarised it2 nor can it again be reflected at a particular angle2 so that in double-refracting crystals1 these two poles1 or polarised beams1 are different in colour1 some stones being opaque to one beam but not to the other1 whilst some are opaque to both4 ,this curious phenomenon1 with this brief1 though somewhat technical explanation1 shows the cause of many of the great charms in precious stones1 for when viewed at one angle they appear of a definite colour1 whilst at another angle they are just as decided in their colour1 which is then entirely different2 and as these angles change as the eye glances on various facets1 the stone assumes a marvellous wealth of the most brilliant and intense colour of kaleidoscopic variety1 even in a stone which may itself be absolutely clear or colourless to ordinary light4 ,such an effect is called pleochroism1 and crystals which show variations in their colour when viewed from different angles1 or by transmitted light1 are called pleochroic1 or pleochromatic--from two ,greek words signifying to colour more4 ,to aid in the examination of this wonderfully beautiful property possessed by precious stones1 a little instrument has been invented called the dichroscope1 its name showing its ,greek derivation1 and meaning--to see colour twice 7twice1 colour1 to see74 ,it is often a part of a polariscope2 frequently a part also of the polarising attachment to the microscope1 and is so simple and ingenious as to deserve detailed explanation4 ,in a small1 brass tube is fixed a double-image prism of calcite or ,iceland spar1 which has been achromatised--that is1 clear1 devoid of colour--and is therefore capable of transmitting light without showing any prismatic effect1 or allowing the least trace of any except the clear light-beam to pass through4 ,at one end of this tube there is a tiny square hole1 the opposite end carrying a small convex lens1 of such a strength or focus as to show the square hole in true focus1 that is1 with perfectly sharp definition1 even up to the corners of the square4 ,on looking through the tube1 the square hole is duplicated1 two squares being seen4 ,the colours of a gem are tested by the stone being put in front of this square1 when the two colours are seen quite distinctly4 ,not only is this a simple means of judging colour1 but it enables a stone to be classified readily4 ,for if the dichroscope shows two images of the same colour1 then it may possibly be a carbuncle1 or a diamond1 as the case may be--for single-refracting stones1 of the first or cubic system1 show two images of the same colour4 ,but if these two colours are different1 then it must be a double-refracting stone1 and according to the particular colours seen1 so is the stone classified1 for each stone has its own identical colour or colours when viewed through this small but useful instrument4 ,how clear and distinct are these changes may be viewed without it in substances strongly dichroic2 for instance1 if common mica is viewed in one direction1 it is transparent as polished plate-glass1 whilst at another angle1 it is totally opaque4 ,chloride of palladium also is blood-red when viewed parallel to its axis1 and transversely1 it is a remarkably bright green4 ,the beryl also1 is sea-green one way and a beautiful blue another2 the yellow chrysoberyl is brown one way and yellow with a greenish cast when viewed another way4 ,the pink topaz shows rose-colour in one direction and yellow in another4 ,these are perhaps the most striking examples1 and are mostly self-evident to the naked eye1 whilst in other cases1 the changes are so delicate that the instrument must be used to give certainty2 some again show changes of colour as the stone is revolved in the dichroscope1 or the instrument revolved round the stone4 ,some stones1 such as the opal1 split up the light-beams as does a prism1 and show a wonderful exhibition of prismatic colour1 which is technically known as a play of colour4 ,the descriptive term opalescence is self-suggesting as to its origin1 which is the noble or precious opal2 this radiates brilliant and rapidly changing iridescent reflections of blue1 green1 yellow and red1 all blending with1 and coming out of1 a curious silky and milky whiteness1 which is altogether characteristic4 ,the moonstone is another example of this peculiar feature which is possessed in a more or less degree by all the stones in the class of pellucid jewels1 but no stone or gem can in any way even rival the curious mixture of opaqueness1 translucency1 silkiness1 milkiness1 fire1 and the steadfast changeable and prismatic brilliance of colour of the precious opal4 ,the other six varieties of opal are much inferior in their strange mixture of these anomalies of light and colour4 ,given in order of value1 we have as the second1 the fire opal with a red reflection1 and1 as a rule1 that only4 ,the third in value is the common opal1 with the colours of green1 red1 white and yellow1 but this is easily distinguishable from the noble or precious variety in that the common opal does not possess that wonderful play of colour4 ,the fourth variety is called the semi-opal1 which is really like the third variety1 the common1 but of a poorer quality and more opaque4 ,the fifth variety in order of value1 is that known as the hydrophane1 which has an interesting characteristic in becoming transparent when immersed in water1 and only then4 ,the sixth is the hyalite1 which has but a glassy or vitreous lustre1 and is found almost exclusively in the form of globules1 or clusters of globules1 somewhat after the form and size of bunches of grapes2 hence the name botryoidal is often applied to this variety4 ,the last and commonest of all the seven varieties of opal is somewhat after the shape of a kidney 7reniform71 or other irregular shape1 occasionally almost transparent1 but more often somewhat translucent1 and very often opaque4 ,this seventh class is called menilite1 being really an opaline form of quartz1 originally found at ,menilmontant1 hence its name 7,menil1 and ,greek lithos1 stone74 ,it is a curious blue on the exterior of the stone1 brown inside4 ,history records many magnificent and valuable opals1 not the least of which was that of ,nonius1 who declined to give it to ,mark ,antony1 choosing exile rather than part with so rare a jewel1 which ,pliny describes as being existent in his day1 and of a value which1 in present ,english computation1 would exceed one hundred thousand pounds4 ,many other stones possess one or more properties of the opal1 and are therefore considered more or less opalescent4 ,this play of colour and opalescence1 must not be confused with change of colour4 ,the two first appear mostly in spots and in brilliant points or flashes of coloured light1 or fire as it is termed4 ,this fire is constantly on the move1 or playing1 whereas change of colour1 though not greatly dissimilar1 is when the fire merely travels over broader surfaces1 each colour remaining constant1 such as when directly moving the stone1 or turning it1 when the broad mass of coloured light slowly changes1 usually to its complementary4 ,thus in this class of stone1 subject to change of colour1 a green light is usually followed by its complementary1 red1 yellow by purple1 blue by orange1 green by brown1 orange by grey1 purple by broken green1 with all the intermediary shades of each4 ,thus when the line of sight is altered1 or the stone moved1 never otherwise1 the colours chase one another over the surface of the gem1 and mostly in broad splashes2 but in those gems possessing play of colour1 strictly speaking1 whilst the stone itself remains perfectly still1 and the sight is fixed unwaveringly upon it1 the pulsations of the blood in the eyes1 with the natural movements of the eyes and eyelids1 even in a fixed1 steady glance1 are quite sufficient to create in the stone a display of sparks and splashes of beautiful fiery light and colour at every tremor4 ,the term iridescence is used when the display of colour is seen on the surface1 rather than coming out of the stone itself4 ,the cause of this is a natural1 or in some cases an accidental1 breaking of the surface of the stone into numerous cobweb-like cracks2 these are often of microscopic fineness1 only perceptible under moderately high powers4 ,nevertheless they are quite sufficient to interfere with and refract the light rays and to split them up prismatically4 ,in some inferior stones this same effect is caused or obtained by the application of a gentle heat1 immersion in chemicals1 subjection to ,x rays and other strong electric influence1 and in many other ways4 ,as a result1 the stone is very slightly expanded1 and as the molecules separate1 there appear on the surface thousands1 perhaps millions1 of microscopic fissures running at all angles1 so that no matter from what position the stone may be viewed1 a great number of these fissures are certain to split up the light into prismatic colours causing brilliant iridescence4 ,similar fissures may often be seen with the naked eye on glass1 especially if scorched or cooled too rapidly 7chilled71 and on the surface of clear spar and mica1 their effects being of extreme interest1 from a colour point of view1 at least4 ,,chapter ,,vii4 ,,physical ,,properties4 ,e--,,hardness4 ,hardness is perhaps one of the most important features in a stone1 especially those of the gem series1 for no matter how colour1 lustre1 general beauty and even rarity may entitle a stone to the designation precious1 unless it possesses great hardness it cannot be used as a gem or jewel4 ,consequently1 the hardness of jewels is a matter of no small importance1 and by dint of indefatigable research1 in tests and comparison1 all known precious stones have been classified in various scales or degrees of hardness4 ,the most popular and reliable table is that of ,mohs1 in which he takes talc as the softest of the rarer minerals and classes this as ,no4 #a2 from that he goes by gradual steps to the diamond1 the hardest of the stones1 which he calls ,no4 #aj1 and between these two all other gems are placed4 ,here is given a complete list of ,mohs's arrangement of stones1 according to their hardness1 beginning at ,no4 #a1 thus3-- ,talc #a ,rock salt #b ,amber #b-a_/b ,calcite #c ,malachite #c-a_/b ,jet #c-a_/b ,fluorspar #d ,apatite #e ,dioptase #e ,kyanite 7various7 #e-g ,haueynite #e-a_/b ,haematite #e-a_/b ,lapis lazuli #e-a_/b ,moldavite 7various7 #e-a_/b-f-a_/b ,rhodonite #e-a_/b-f-a_/b ,obsidian #e-a_/b ,sphene #e-a_/b ,opal 7various7 #e-a_/b-f-a_/b ,nephrite #e-c_/d ,chrysolite #f-g ,felspar #f ,adularia #f ,amazon stone #f ,diopside #f ,iron pyrites #f ,labradorite #f ,turquoise #f ,spodumene #f-a_/b-g ,the ,chalcedony group which embraces the ,agate1 ,carnelian1 etc4 #f-a_/b ,demantoid #f-a_/b ,epidote #f-a_/b ,idocrase #f-a_/b ,garnets 7see also ,red ,garnets below7 #f-a_/b-g-a_/b ,axinite #f-c_/d ,jadeite #f-c_/d ,quartz1 including ,rock-crystal1 ,amethyst1 ,jasper1 ,chrysoprase ,citrine1 etc4 #g ,jade #g ,dichorite 7water sapphire7 #g-g-a_/b ,cordierite #g-a_/d ,red ,garnets 7see also ,garnets above7 #g-a_/d ,tourmaline #g-a_/d ,andalusite #g-a_/b ,euclase #g-a_/b ,staurolite #g-a_/b ,zircon #g-a_/b ,emerald1 ,aquamarine1 or ,beryl #g-c_/d ,phenakite #g-c_/d ,spinel #h ,topaz #h ,chrysoberyl #h-a_/b ,the ,corundum group embracing the ,ruby1 ,sapphire1 etc4 #i ,diamond #aj 7,see also list of stones1 arranged in their respective colours1 in ,chapter ,,xii47 ,the method of testing is very simple4 ,a representative selection of the above stones1 each with a sharp edge1 is kept for the purpose of scratching and being scratched1 and those usually set apart for tests in the various groups1 are as follows3-- #a ,talc #b ,rock-salt1 or ,gypsum #c ,calcite #d ,fluorspar #e ,apatite #f ,felspar #g ,quartz #h ,topaz #i ,corundum #aj ,diamond ,the stone under examination may perhaps first be somewhat roughly classified by its colour1 cleavage1 and general shape4 ,one of these standard stones is then gently rubbed across its surface and then others of increasingly higher degrees1 till no scratch is evident under a magnifying glass4 ,thus if quartz ceases to scratch it1 but a topaz will do so1 the degree of hardness must lie between #g and #h4 ,then we reverse the process3 the stone is passed over the standard1 and if both quartz and topaz are scratched1 then the stone is at least equal in hardness to the topaz1 and its classification becomes an easy matter4 ,instead of stones1 some experts use variously-tempered needles of different qualities and compositions of iron and steel4 ,for instance1 a finely-tempered ordinary steel needle will cut up to ,no4 #f stones2 one made of tool steel1 up to #g2 one of manganese steel1 to #g-a_/b2 one made of high-speed tool steel1 to #h and #h-a_/b1 and so on1 according to temper2 so that from the scratch which can be made with the finger-nail on mica1 to the hardness of the diamond1 which diamond alone will scratch readily1 the stones may be picked out1 classified and tested1 with unerring accuracy4 ,it will thus be seen how impossible it is1 even in this one of many tests1 for an expert to be deceived in the purchase of precious stones1 except through gross carelessness--a fault seldom1 if ever1 met with in the trade4 ,for example--a piece of rock-crystal1 chemically coloured1 and cut to represent a ruby1 might appear so like one as to deceive a novice1 but the mere application to its surface of a real ruby1 which is hardness #i1 or a ,no4 #i needle1 would reveal too deep or powdery a scratch2 also its possibility of being scratched by a topaz or a ,no4 #h needle1 would alone prove it false1 for the corundum group1 being harder than ,no4 #h1 could not be scratched by it4 ,so would the expert go down the scale1 the tiny scratches becoming fainter as he descended1 because he would be approaching more nearly the hardness of the stone under test1 till he arrived at the felspar1 ,no4 #f1 which would be too soft to scratch it1 yet the stone would scratch the felspar1 but not zircon or andalusite1 #g-a_/b1 or topaz1 #h1 so that his tests would at once classify the stone as a piece of cut and coloured quartz1 thus confirming what he would1 at the first sight1 have suspected it to be4 ,the standard stones themselves are much more certain in results than the needles1 which latter1 though well selected and tempered1 are not altogether reliable1 especially in the more delicate distinctions of picking out the hardest of certain stones of the same kind1 in which cases only the expert judge can decide with exactness4 ,accurate in this the expert always is1 for he judges by the sound and depth of his cut1 and by the amount and quality of the powder1 often calling the microscope to his aid1 so that when the decision is made finally1 there is never the least doubt about it4 ,rapidly as these tests can be made1 they are extremely reliable1 and should the stone be of great value1 it is also subjected to other unerring tests of extreme severity1 any one of which would prove it false1 if it chanced to be so1 though some stones are manufactured and coloured so cleverly that to all but the expert judge and experienced dealer1 they would pass well for the genuine4 ,in ,mohs's list it will be seen that several stones vary considerably1 the opal1 for instance1 having a degree of hardness from #e-a_/b to #f-a_/b inclusive4 ,all stones differ slightly1 though almost all may be said to fit their position in the scale2 but in the case of the opal1 the difference shown is partly due to the many varieties of the stone1 as described in the last chapter4 ,in applying this test of hardness to a cut gem1 it will be noticed that some parts of the same stone seem to scratch more readily than others1 such as on a facet at the side1 which is often softer than those nearest the widest part of the stone1 where the claws1 which hold it in its setting1 usually come4 ,this portion is called the girdle1 and it is on these girdle facets that the scratches are generally made4 ,this variation in hardness is mostly caused by cleavage1 these cleavage planes showing a marked1 though often but slight1 difference in the scratch1 which difference is felt rather than seen4 ,in addition to the peculiar feel of a cutting scratch1 is the sound of it4 ,on a soft stone being cut by a hard one1 little or no sound is heard1 but there will form a plentiful supply of powder1 which1 on being brushed off1 reveals a more or less deep incision4 ,but as the stones approach one another in hardness1 there will be little powder and a considerable increase in the noise2 for the harder are the stones1 cutting and being cut1 the louder will be the sound and the less the powder4 ,an example of this difference is evident in the cutting of ordinary glass with a set or glazier's diamond1 and with a nail4 ,if the diamond is held properly1 there will be heard a curious sound like a keen1 drawn-out kiss1 the diamond being considerably harder than the material it cut4 ,an altogether different sound is that produced by the scratching of glass with a nail4 ,in this case1 the relative difference in hardness between the two is small1 so that the glass can only be scratched and not cut by the nail2 it is too hard for that1 so the noise is much greater and becomes a screech4 ,experience1 therefore1 makes it possible to tell to a trifle1 at the first contact1 of what the stone is composed1 and in which class it should be placed1 by the mere feel of the scratch1 the depth of it1 the amount and kind of powder it leaves1 and above all1 by the sound made1 which1 even in the tiniest scratch1 is quite characteristic4 ,,chapter ,,viii4 ,,physical ,,properties4 ,f--,,specific ,,gravity4 ,the fixing of the specific gravity of a stone also determines its group position with regard to weight2 its colour and other characteristics defining the actual stone4 ,this is a safe and very common method of proving a stone1 since its specific gravity does not vary more than a point or so in different specimens of the same stone4 ,there are several ways of arriving at this1 such as by weighing in balances in the usual manner1 by displacement1 and by immersion in liquids the specific gravity of which are known4 ,cork is of less specific gravity than water1 therefore it floats on the surface of that liquid1 whereas iron1 being heavier1 sinks4 ,so that by changing the liquid to one lighter than cork1 the cork will sink in it as does iron in water2 in the second instance1 if we change the liquid to one heavier than iron1 the iron will float on it as does cork on water1 and exactly as an ordinary flat-iron will float on quicksilver1 bobbing up and down like a cork in a tumbler of water4 ,if1 therefore1 solutions of known but varying densities are compounded1 it is possible to tell almost to exactitude the specific gravity of any stone dropped into them1 by the position they assume4 ,thus1 if we take a solution of pure methylene iodide1 which has a specific gravity of #c4biha1 and into this drop a few stones selected indiscriminately1 the effect will be curious3 first1 some will sink plump to the bottom like lead2 second1 some will fall so far quickly1 then remain for a considerable time fairly stationary2 third1 some will sink very slowly2 fourth1 some will be partially immersed1 that is1 a portion of their substance being above the surface of the liquid and a portion covered by it2 fifth1 some will float on the surface without any apparent immersion4 ,in the first case1 the stones will be much heavier than #c4biha2 in the second1 the stones will be about #c4ej2 in the third and fourth instances1 the stones will be about the same specific gravity as the liquid1 whilst in the fifth1 they will be much lighter1 and thus a rough but tolerably accurate isolation may be made4 ,on certain stones being extracted and placed in other liquids of lighter or denser specific gravity1 as the case may be1 their proper classification may easily be arrived at1 and if the results are checked by actual weight1 in a specific gravity balance1 they will be found to be fairly accurate4 ,the solution commonly used for the heaviest stones is a mixture of nitrate of thallium and nitrate of silver4 ,this double nitrate has a specific gravity of #d4gifc1 therefore such a stone as zircon1 which is the heaviest known1 will float in it4 ,for use1 the mixture should be slightly warmed till it runs thin and clear2 this is necessary1 because at #fj deg4 7taking this as ordinary atmospheric temperature7 it is a stiff mass4 ,a lighter liquid is a mixture of iodide of mercury in iodide of potassium1 but this is such an extremely corrosive and dangerous mixture1 that the more common solution is one in which methylene iodide is saturated with a mixture of iodoform until it shows a specific gravity of #c4fja2 and by using the methylene iodide alone1 in its pure state1 it having a specific gravity of #c4biha1 the stones to that weight can be isolated1 and by diluting this with benzole1 its weight can be brought down to that of the benzole itself1 as in the case of ,sonstadt's solution4 ,this solution1 in full standard strength1 has a specific gravity of #c4aghi1 but may be weakened by the addition of distilled water in varying proportions till the weight becomes almost that of water4 ,knowing the specific gravity of all stones1 and dividing them into six groups1 by taking a series of standard solutions selected from one or other of the above1 and of known specific gravity1 we can judge with accuracy if any stone is what it is supposed to be1 and classify it correctly by its mere floating or sinking when placed in these liquids4 ,beginning then with the pure double nitrate of silver and thallium1 this will isolate the stones of less specific gravity than #d4gifc1 and taking the lighter solutions and standardising them1 we may get seven solutions which will isolate the stones as follows3-- ,a shows the stones which have #d4gifc a specific gravity over ,b #c4gj and under #d4gifc ,c #c4ej #c4gj ,d #c4jj #c4ej ,e #b4ej #c4jj ,f #b4jj #b4ej ,g -- -- under #b4jj ,therefore each liquid will isolate the stones in its own group by compelling them to float on its surface2 commencing with the heaviest and giving to the groups the same letters as the liquids1 it is seen that-- ,group ,a4--,isolates gems with a specific gravity of #d4gifc and over #d4gj2 in this group is placed zircon1 with a specific gravity of from #d4gj to #d4hh4 ,group ,b4--,stones whose specific gravity lies between #c4gj and under #d4gifc4 ,garnets1 many varieties4 ,see ,group ,d below4 ,almandine #d4aa and occasionally to #d4be ,ruby #d4jgc #d4jhj ,sapphire #d4jdi #d4jfj ,corundum #c4ij #d4af ,cape ,ruby #c4hfa ,demantoid #c4hae ,staurolite #c4gce ,malachite #c4gaj and occasionally to #c4iif ,group ,c4--,stones whose specific gravity lies between #c4ej and under #c4gj4 ,pyrope 7average7 #c4fhb ,chrysoberyl #c4fhi and occasionally to #c4geb ,spinel #c4fad #c4fed ,kyanite #c4fji #c4fhh ,hessonite #c4fjc #c4fea ,diamond #c4ejb #c4efd ,topaz #c4ejj #c4ebj ,group ,d4--,stones whose specific gravity lies between #c and under #c4ej4 ,rhodonite #c4dac and occasionally to #c4fag ,garnets #c4djj #d4ejj ,epidote #c4cfj #c4dhj ,sphene #c4cdh and occasionally to #c4dbj ,idocrase #c4cdf #c4daj ,olivine #c4ccd #c4cfh ,chrysolite #c4caf #c4ebh ,jade #c4cjj #c4cha ,jadeite #c4bii ,axinite #c4bie ,dioptase #c4bhi ,diopside #b4bgi ,tourmaline 7yellow7 #c4baj ,andalusite #c4bjd ,apatite #c4aij ,tourmaline 7,blue and ,violet7 #c4afj ,tourmaline 7,green7 #c4adh 7,red7 #c4ajj ,spodumene #c4acj and occasionally to #c4bjj ,euclase #c4jij ,fluorspar #c4jca and occasionally to #c4bjj ,tourmaline 7,colourless7 #c4jbi ,tourmaline 7,blush ,rose7 #c4jbd ,tourmaline 7,black7 #c4jbd and occasionally to #c4cjj ,nephrite #c4jai ,group ,e4--,stones whose specific gravity lies between #b4ej and under #c4jjj4 ,phenakite #b4ife ,turquoise #b4hjj ,beryl #b4gji and occasionally to #b4ha ,aquamarine #b4gja #b4hj ,labradorite #b4gjj ,emerald #b4fij ,quartz #b4fgj ,chrysoprase #b4fgj ,jasper #b4ffh ,amethyst #b4ffa ,hornstone #b4feh ,citrine #b4feh ,cordierite #b4fda ,agate #b4faj ,chalcedony #b4eih and occasionally to #b4faj ,adularia #b4efg ,rock-crystal #b4eba and occasionally to #b4gie ,group ,f4--,stones whose specific gravity lies between #b4jj and under #b4ej4 ,haueynite #b4dgj and occasionally to #b4dia ,lapis lazuli #b4dfa ,moldavite #b4ced ,opal #b4afj and according to variety to #b4bhc 7,fire ,opal7 #b4baj 7average7 ,group ,g4--,stones whose specific gravity is under #b4jj4 ,jet #a4cdh ,amber #a4jjj 7,see also list of stones1 arranged in their respective colours1 in ,chapter ,,xii47 ,in many of these cases the specific gravity varies from 4#aa to 4#bj1 but the above are the average figures obtained from a number of samples specially and separately weighed4 ,in some instances this difference may cause a slight overlapping of the groups1 as in group ,c1 where the chrysoberyl may weigh from #c4fhi to #c4geb1 thus bringing the heavier varieties of the stone into group ,b1 but in all cases where overlapping occurs1 the colour1 form1 and the self-evident character of the stone are in themselves sufficient for classification1 the specific gravity proving genuineness4 ,this is especially appreciated when it is remembered that so far science has been unable 7except in very rare instances of no importance7 to manufacture any stone of the same colour as the genuine and at the same time of the same specific gravity4 ,either the colour and characteristics suffer in obtaining the required weight or density1 or if the colour and other properties of an artificial stone are made closely to resemble the real1 then the specific gravity is so greatly different1 either more or less1 as at once to stamp the jewel as false4 ,in the very few exceptions where chemically-made gems even approach the real in hardness1 colour1 specific gravity1 c41 they cost so much to obtain and the difficulties of production are so great that they become mere chemical curiosities1 far more costly than the real gems4 ,further1 they are so much subject to chemical action1 and are so susceptible to their surroundings1 that their purity and stability cannot be maintained for long even if kept airtight2 consequently these ultra-perfect imitations are of no commercial value whatever as jewels1 even though they may successfully withstand two or three tests4 ,,chapter ,,ix4 ,,physical ,,properties4 ,g--,,heat4 ,another method of isolating certain stones is by the action of heat-rays4 ,remembering our lessons in physics we recall that just as light-rays may be refracted1 absorbed1 or reflected1 according to the media through which they are caused to pass1 so do heat-rays possess similar properties4 ,therefore1 if heat-rays are projected through precious stones1 or brought to bear on them in some other manner than by simple projection1 they will be refracted1 absorbed1 or reflected by the stones in the same manner as if they were light-rays1 and just as certain stones allow light to pass through their substance1 whilst others are opaque1 so do some stones offer no resistance to the passage of heat-rays1 but allow them free movement through the substance1 whilst1 in other cases1 no passage of heat is possible1 the stones being as opaque to heat as to light4 ,indeed1 the properties of light and heat are in many ways identical1 though the test by heat must in all cases give place to that by light1 which latter is by far of the greater importance in the judging and isolation of precious stones4 ,it will readily be understood that in the spectrum the outer or extreme light-rays at each side are more or less bent or diverted1 but those nearest the centre are comparatively straight1 so that1 as before remarked1 these central rays are taken as being the standard of light-value4 ,this divergence or refraction is greater in some stones than in others1 and to it the diamond1 as an example1 owes its chief charm4 ,in just such manner do certain stones refract1 absorb1 or reflect heat2 thus amber1 gypsum1 and the like1 are practically opaque to heat-rays1 in contrast with those of the nature of fluorspar1 rock-salt1 c41 which are receptive4 ,heat passes through these as easily as does light through a diamond1 such stones being classed as diathermal 7to heat through74 ,so that all diathermal stones are easily permeable by radiant heat1 which passes through them exactly as does light through transparent bodies4 ,others1 again1 are both single and double refracting to heat-rays1 and it is interesting to note the heat-penetrating value as compared with the refractive indexes of the stone4 ,in the following table will be found the refractive indexes of a selection of single and double refractive stones1 the figures for ,light being taken from a standard list4 ,the second column shows the refractive power of heat1 applied to the actual stones1 and consisting of a fine pencil blowpipe-flame1 one line 7the one twelfth part of an inch7 in length in each case4 ,this list must be taken as approximate1 since in many instances the test has been made on one stone only1 without possibility of obtaining an average2 and as stones vary considerably1 the figures may be raised or lowered slightly1 or perhaps even changed in class1 because in some stones the least stain or impurity may cause the heat effects to be altered greatly in their character1 and even to become singly or doubly refracting1 opaque or transparent1 to heat-rays1 according to the nature of the impurity or to some slight change in the crystalline structure1 and so on4 ,selection of ,singly refracting stones4 ,indexes of ,rays of ,,light4 ,,heat4 ,fluorspar #a4dcf #d4aj varies ,opal #a4dgi #b4aj ,spinel #a4gbf #a4jj ,almandine #a4gfd #a4jj ,diamond #b4dca #f4aa double ,selection of ,doubly refracting stones4 ,indexes of ,rays of ,,light4 ,,heat4 ,quartz #a4ede #d4g single and double ,beryl #a4ege #a4j varies considerably ,topaz #a4fce #d4a ,chrysoberyl #a4gfe #a4a ,ruby #a4idi #e4a single and double ,the tourmaline has a light-refractive index of #a4fc1 with a heat index of none1 being to heat-rays completely opaque4 ,the refractive index of gypsum is #a4ed1 but heat none1 being opaque4 ,the refractive index of amber is #a4ea1 but heat none1 being opaque4 ,in some of the specimens the gypsum showed a heat-penetration index of #j4jja1 and amber of #j4jef1 but mostly not within the third point4 ,in all cases the heat-penetration and refraction were shown by electric recorders4 ,these figures are the average of those obtained from tests made in some cases on several stones of the same kind1 and also on isolated specimens4 ,not only does the power of the stone to conduct heat vary in different stones of the same kind or variety1 as already explained1 but there is seen a remarkable difference in value1 according to the spot on which the heat is applied1 so that on one stone there is often seen a conductivity varying between #j4ae to #d4gj4 ,this is owing to the differences of expansion due to the temporary disturbance of its crystalline structure1 brought about by the applied heat4 ,this will be evident when heat is applied on the axes of the crystal1 on their faces1 angles1 lines of symmetry1 etc41 etc41 each one of which gives different results1 not only as to value in conductivity1 but a result which varies in a curious degree1 out of all proportion to the heat applied4 ,in many cases a slight diminution in applied heat gives a greater conductivity1 whilst in others a slight rise in the temperature of the heat destroys its conductivity altogether1 and renders the stone quite opaque to heat-rays4 ,this anomaly is due entirely to the alteration of crystalline structure1 which1 in the one case1 is so changed by the diminution in heat as to cause the crystals to be so placed that they become diathermal1 or transparent to heat-rays2 whilst1 in the other instance1 the crystals which so arrange themselves as to be diathermal are1 by a slightly increased temperature1 somewhat displaced1 and reflect1 or otherwise oppose the direct passage of heat-rays1 which1 at the lower temperature1 obtained free passage4 ,thus certain stones become both opaque and diathermal1 and as the heat is caused to vary1 so do they show the complete gamut between the two extremes of total opacity and complete transparency to heat-rays4 ,for the purpose under consideration1 the temperature of the pencil of heat applied to the stones in their several portions was kept constant4 ,it will be seen1 therefore1 that no great reliance can be placed on the heat test as applied to precious stones4 ,,chapter ,x4 ,,physical ,,properties4 ,h--,,magnetic ,,and ,,electric ,,influences4 ,the word electricity is derived from the ,greek elektron1 which was the name for amber1 a mineralised resin of extinct pine-trees4 ,it was well-known to the people of pre-historic times2 later to the early ,egyptians1 and1 at a still later date1 we have recorded how ,thales--the ,greek philosopher1 who lived about the close of the #gth ,century ,b4,c41 and was one of the seven wise men--discovered the peculiar property which we call electricity by rubbing dry silk on amber4 ,many stones are capable of exhibiting the same phenomenon1 not only by friction1 as in ,thales's experiment1 but also under the influence of light1 heat1 magnetism1 chemical action1 pressure1 etc41 and of holding or retaining this induced or added power for a long or short period1 according to conditions and environment4 ,if a small pith ball is suspended from a non-conducting support1 it forms a simple and ready means of testing the electricity in a stone4 ,according to whether the ball is repelled or attracted1 so is the electricity in the stone made evident1 though the electroscope gives the better results4 ,by either of these methods it will be found that some of the stones are more capable of giving and receiving charges of electricity than are others2 also that some are charged throughout with one kind only1 either positive or negative1 whilst others have both1 becoming polarised electrically1 having one portion of their substance negative1 the other positive4 ,for instance1 amber1 as is well known1 produces negative electricity under the influence of friction1 but in almost all cut stones1 other than amber1 the electricity produced by the same means is positive1 whereas in the uncut stones the electricity is negative1 with the exception of the diamond1 in which the electricity is positive4 ,when heated1 some stones lose their electricity2 others develop it1 others have it reversed1 the positive becoming negative and vice versa2 others again1 when heated1 become powerfully magnetic and assume strong polarity4 ,when electricity develops under the influence of heat1 or is in any way connected with a rising or falling of temperature in a body1 it is called pyro-electricity1 from the ,greek word pyros1 fire4 ,the phenomenon was first discovered in the tourmaline1 and it is observed1 speaking broadly1 only in those minerals which are hemimorphic1 that is1 where the crystals have different planes or faces at their two ends1 examples of which are seen in such crystals as those of axinite1 boracite1 smithsonite1 topaz1 etc41 all of which are hemimorphic4 ,taking the tourmaline as an example of the pyro-electric minerals1 we find that when this is heated to between #ej deg4 ,f4 and #cjj deg4 ,f4 it assumes electric polarity1 becoming electrified positively at one end or pole and negatively at the opposite pole4 ,if it is suspended on a silken thread from a glass rod or other non-conducting support in a similar manner to the pith ball1 the tourmaline will be found to have become an excellent magnet4 ,by testing this continually as it cools there will soon be perceived a point which is of extreme delicacy of temperature1 where the magnetic properties are almost in abeyance4 ,but as the tourmaline cools yet further1 though but a fraction of a degree1 the magnetic properties change2 the positive pole becomes the negative1 the negative having changed to the positive4 ,it is also interesting to note that if the tourmaline is not warmed so high as to reach a temperature of #ej deg4 ,f41 or is heated so strongly as to exceed more than a few degrees above #cjj deg4 ,f41 then these magnetic properties do not appear1 as no polarity is present4 ,this polarity1 or the presence of positive and negative electricity in one stone1 may be strikingly illustrated in a very simple manner3--,if a little sulphur and red-lead1 both in fine powder1 are shaken up together in a paper or similar bag1 the moderate friction of particle against particle electrifies both2 one negatively1 the other positively4 ,if1 then1 a little of this now golden-coloured mixture is gently dusted over the surface of the tourmaline or other stone possessing electric polarity1 a most interesting change is at once apparent4 ,the red-lead separates itself from the sulphur and adheres to the negative portion of the stone1 whilst the separated sulphur is at once attracted to the positive end1 so that the golden-coloured mixture becomes slowly transformed into its two separate components--the brilliant yellow sulphur1 and the equally brilliant red-lead4 ,these particles form in lines and waves around the respective poles in beautiful symmetry1 their positions corresponding with the directions of the lines of magnetic force1 exactly as will iron filings round the two poles of a magnet4 ,from this it will clearly be seen how simple a matter it is to isolate the topaz1 tourmaline1 and all the pyro-electric stones from the non-pyro-electric1 for science has not as yet been able to give to spurious stones these same electric properties1 however excellent some imitations may be in other respects4 ,further1 almost all minerals lose their electricity rapidly on exposure to atmospheric influences1 even to dry air2 the diamond retains it somewhat longer than most stones1 though the sapphire1 topaz1 and a few others retain it almost as long again as the diamond1 and these electric properties are some of the tests which are used in the examination of precious stones4 ,those stones which show electricity on the application of pressure are such as the fluorspar1 calcite1 and topaz4 ,with regard to magnetism1 the actual cause of this is not yet known with certainty4 ,it is1 of course1 a self-evident fact that the magnetic iron ore1 which is a form of peroxide1 commonly known as magnetite1 or lodestone1 has the power of attracting a magnet when swinging free1 or of being attracted by a magnet1 to account for which many plausible reasons have been advanced4 ,perhaps the most reasonable and acceptable of these is that this material contains molecules which have half their substance positively and the other half negatively magnetised4 ,substances so composed1 of which magnets are an example1 may be made the means of magnetising other substances by friction1 without they themselves suffering any loss2 but it is not all substances that will respond to the magnet4 ,for instance1 common iron pyrites1 ,fe,s#b1 is unresponsive1 whilst the magnetic pyrites1 which varies from #e;,fe,s1 ,fe#b,s#c1 to #f;,fe,s1 ,fe#b,s#c1 and is a sulphide of iron1 is responsive both positively and negatively4 ,bismuth and antimony also are inactive1 whilst almost all minerals containing even a small percentage of iron will deflect the magnetic needle1 at least under the influence of heat4 ,so that from the lodestone--the most powerfully magnetic mineral known--to those minerals possessing no magnetic action whatever1 we have a long1 graduated scale1 in which many of the precious stones appear1 those containing iron in their composition being more or less responsive1 as already mentioned1 and that either in their normal state1 or when heated1 and always to an extent depending on the quantity or percentage of iron they contain4 ,in this case1 also1 science has not as yet been able to introduce into an artificial stone the requisite quantity of iron to bring it the same analytically as the gem it is supposed to represent1 without completely spoiling the colour4 ,so that the behaviour of a stone in the presence of a magnet1 to the degree to which it should or should not respond1 is one of the important tests of a genuine stone4 ,,chapter ,,xi4 ,,the ,,cutting ,,of ,,precious ,,stones4 ,as existing in a state of nature precious stones do not1 as a rule1 exhibit any of those beautiful and wonderful properties which cause them to be so admired and sought after as to become of great intrinsic value1 for their surfaces have become clouded by innumerable fine cuts or abrasions1 because of the thousands of years during which they have been under pressure1 or tumbled about in rivers1 or subjected to the incessant friction caused by surrounding substances4 ,all this occurring above and under ground has given them an appearance altogether different to that which follows cutting and polishing4 ,further1 the shape of the stone becomes altered by the same means1 and just as ,michael ,angelo's figure was already in the marble1 as he facetiously said1 and all he had to do was to chip off what he did not require till he came to it1 so is the same process of cutting and polishing necessary to give to the precious stones their full value1 and it is the manner in which these delicate and difficult operations are performed that is now under consideration4 ,just as experience and skill are essential to the obtaining of a perfect figure from the block of marble1 so must the cutting and polishing of a precious stone call for the greatest dexterity of which a workman is capable1 experience and skill so great as to be found only in the expert1 for in stones of great value even a slight mistake in the shaping and cutting would probably not only be wasteful of the precious material1 but would utterly spoil its beauty1 causing incalculable loss1 and destroying altogether the refrangibility1 lustre and colour of the stone1 thus rendering it liable to easy fracture3 in every sense converting what would have been a rare and magnificent jewel to a comparatively valueless specimen4 ,one of the chief services rendered by precious stones is that they may be employed as objects of adornment1 therefore1 the stone must be cut of such a shape as will allow of its being set without falling out of its fastening--not too shallow or thin1 to make it unserviceable and liable to fracture1 and in the case of a transparent stone1 not too deep for the light to penetrate1 or much colour and beauty will be lost4 ,again1 very few stones are flawless1 and the position in which the flaw or flaws appear will1 to a great extent1 regulate the shape of the stones1 for there are some positions in which a slight flaw would be of small detriment1 because they would take little or no reflection1 whilst in others1 where the reflections go back and forth from facet to facet throughout the stone1 a flaw would be magnified times without number1 and the value of the stone greatly reduced4 ,it is therefore essential that a flaw should be removed whenever possible1 but1 when this is not practicable1 the expert will cut the stone into such a shape as will bring the defect into the least important part of the finished gem1 or probably sacrifice the size and weight of the original stone by cutting it in two or more pieces of such a shape that the cutting and polishing will obliterate the defective portions4 ,such a method was adopted with the great ,cullinan diamond1 as described in ,chapter ,,iv4 ,from this remarkable diamond a great number of magnificent stones were obtained1 the two chief being the largest and heaviest at present known4 ,some idea of the size of the original stone may be gathered from the fact that the traditional ,indian diamond1 the ,great ,mogul1 is said to have weighed #bhj carats4 ,this stone1 however1 is lost1 and some experts believe that it was divided1 part of it forming the present famous ,koh-i-nur2 at any rate1 all trace of the ,great ,mogul ceased with the looting of ,delhi in #agci4 ,the ,koh-i-nur weighs a little over #ajf carats2 before cutting it weighed a shade over #ahf2 the ,cullinan1 in the same state1 weighed nearly #cbed carats4 ,this massive diamond was cut into about #bjj stones1 the largest1 now placed in ,the ,royal ,sceptre with the ,cross1 weighing #eaf-a_/b carats1 the second1 now placed under the historic ruby in ,the ,imperial ,state ,crown1 weighing #cji-c_/afths carats4 ,these two diamonds are now called ,the ,stars of ,africa4 ,both these stones1 but especially the larger1 completely overshadow the notorious ,koh-i-nur1 and notwithstanding the flaw which appeared in the original stone1 every one of the resulting pieces1 irrespective of weight1 is without the slightest blemish and of the finest colour ever known1 for the great ,south ,african diamond is of a quality never even approached by any existing stone1 being ideally perfect4 ,it requires a somewhat elaborate explanation to make clear the various styles of cut without illustrations4 ,they are usually divided into two groups1 with curved1 and with flat or plane surfaces4 ,of the first1 the curved surfaces1 opaque and translucent stones1 such as the moonstone1 cat's-eye1 etc41 are mostly cut en cabochon1 that is1 dome-shaped or semi-circular at the top1 flat on the underside1 and when the garnet is so cut it is called a carbuncle4 ,in strongly coloured stones1 while the upper surface is semi-circular like the cabochon1 the under surface is more or less deeply concave1 sometimes following the curve of the upper surface1 the thickness of the stone being in that case almost parallel throughout4 ,this is called the hollow cabochon4 ,other stones are cut so that the upper surface is dome-shaped like the last two1 but the lower is more or less convex1 though not so deep as to make the stone spherical4 ,this is called the double cabochon4 ,a further variety of cutting is known as the goutte de suif1 or the tallow-drop1 which takes the form of a somewhat flattened or long-focus double-convex lens4 ,the more complicated varieties of cut are those appearing in the second group1 or those with plane surfaces4 ,a very old form is the rose or rosette2 in this the extreme upper centre1 called the crown1 or star1 is usually composed of six triangles1 the apexes of which are elevated and joined together1 forming one point in the centre4 ,from their bases descend a further series of triangles1 the bases and apexes of which are formed by the bases and lower angles of the upper series4 ,this lower belt is called the teeth1 under which the surface or base of the stone is usually flat1 but sometimes partakes of a similar shape to the upper surface1 though somewhat modified in form4 ,another variety is called the table cut1 and is used for coloured stones4 ,it has a flat top or table of a square or other shape1 the edges of which slope outwards and form the bezils or that extended portion by which the stone is held in its setting4 ,it will thus be seen that the outside of the stone is of the same shape as that of the table1 but larger1 so that from every portion of the table the surface extends downwards1 sloping outwards to the extreme size of the stone1 the underside sloping downwards and inwards to a small and flat base1 the whole1 in section1 being not unlike the section of a pegtop4 ,a modification of this is known as the step cut1 sometimes also called the trap4 ,briefly1 the difference between this and the last is that whereas the table has usually one bevel on the upper and lower surfaces1 the trap has one or more steps in the sloping parts1 hence its name4 ,the most common of all1 and usually applied only to the diamond1 is the brilliant cut4 ,this is somewhat complicated1 and requires detailed description4 ,in section1 the shape is substantially that of a pegtop with a flat table top and a small flat base4 ,the widest portion is that on which the claws1 or other form of setting1 hold it securely in position4 ,this portion is called the girdle1 and if we take this as a defining line1 that portion which appears above the setting of this girdle1 is called the crown2 the portion below the girdle is called the culasse1 or less commonly the pavilion4 ,commencing with the girdle upwards1 we have eight cross facets in four pairs1 a pair on each side2 each pair having their apexes together1 meeting on the four extremities of two lines drawn laterally at right angles through the stone4 ,it will1 therefore1 be seen that one side of each triangle coincides with the girdle1 and as their bases do not meet1 these spaces are occupied by eight small triangles1 called skill facets1 each of which has1 as its base1 the girdle1 and the outer of its sides coincides with the base of the adjoining cross facet4 ,the two inner sides of each pair of skill facets form the half of a diamond or lozenge-shaped facet1 called a quoin1 of which there are four4 ,the inner or upper half of each of these four quoins forms the bases of two triangles1 one at each side1 making eight in all1 which are called star facets1 and the inner lines of these eight star facets form the boundary of the top of the stone1 called the table4 ,the inner lines also of the star facets immediately below the table and those of the cross facets immediately above the girdle form four templets1 or bezils4 ,we thus have above the girdle1 thirty-three facets3 #h cross1 #h skill1 #d quoin1 #h star1 #a table1 and #d templets4 ,reversing the stone and again commencing at the girdle1 we have eight skill facets1 sometimes called the lower skill facets1 the bases of which are on the girdle1 their outer sides forming the bases of eight cross facets1 the apexes of which meet on the extremities of the horizontal line1 as in those above the girdle4 ,if the basal lines of these cross facets1 where they join the sides of the skill facets1 are extended to the peak1 or narrow end of the stone1 these lines1 together with the sides of the cross facets1 will form four five-sided facets1 called the pavilions2 the spaces between these four pavilions have their ends nearest the girdle formed by the inner sides of the skill facets1 and of these spaces1 there will1 of course1 be four1 which also are five-sided figures1 and are called quoins1 so that there are eight five-sided facets--four large and four narrow--their bases forming a square1 with a small portion of each corner cut away2 the bases of the broader pavilions form the four sides1 whilst the bases of the four narrower quoins cut off the corners of the square1 and this flat portion1 bounded by the eight bases1 is called the culet1 but more commonly collet4 ,so that below the girdle1 we find twenty-five facets3 #h cross1 #h skill1 #d pavilion1 #d quoin1 and #a collet4 ,these1 with the #cc of the crown1 make #eh1 which is the usual number of facets in a brilliant1 though this varies with the character1 quality1 and size of the diamond4 ,for instance1 though this number is considered the best for normal stones1 specially large ones often have more1 otherwise there is danger of their appearing dull1 and it requires a vast amount of skill and experience to decide upon the particular number and size of the facets that will best display the fire and brilliance of a large stone1 for it is obvious that if1 after months of cutting and polishing1 it is found that a greater or smaller number of facets ought to have been allowed1 the error cannot be retrieved without considerable loss1 and probable ruin to the stone4 ,in the case of the ,cullinan diamonds1 the two largest of which are called the ,stars of ,africa1 #gd facets were cut in the largest portion1 while in the next largest the experts decided to make #ff1 and1 as already pointed out1 these stones are1 up to the present time1 the most magnificent in fire1 beauty and purity ever discovered4 ,the positions and angles of the facets1 as well as the number1 are of supreme importance1 and diamond cutters--even though they have rules regulating these matters1 according to the weight and size of the stone--must exercise the greatest care and exactitude1 for their decision once made is practically unalterable4 ,,chapter ,,xii4 ,,imitations1 ,,and ,,some ,,of ,,the ,,tests1 ,,of ,,precious ,,stones4 ,we now arrive at the point where it is necessary to discuss the manufacture and re-formation of precious stones1 and also to consider a few of the tests which may be applied to all stones4 ,these are given here in order to save needless repetition2 the tests which are specially applicable to individual stones will more properly be found under the description of the stone referred to1 so that the present chapter will be devoted chiefly to generalities4 ,with regard to diamonds1 the manufacture of these has not as yet been very successful4 ,as will be seen on reference to ,chapter ,,ii41 on the ,origin of ,precious ,stones1 it is generally admitted that these beautiful and valuable minerals are caused by chemically-charged water and occasionally1 though not always1 high temperature1 but invariably beautified and brought to the condition in which they are obtained by the action of weight and pressure1 extending unbroken through perhaps ages of time4 ,in these circumstances1 science1 though able to give chemical properties and pressure1 cannot1 of course1 maintain these continuously for ages1 therefore the chemist must manufacture the jewels in such manner that he may soon see the results of his labours1 and though real diamonds may be made1 and with comparative ease1 from boron in the amorphous or pure state along with aluminium1 fused in a crucible at a high temperature1 these diamonds are but microscopic1 nor can a number of them be fused1 or in any other way converted into a large single stone1 so that imitation stones1 to be of any service must be made of a good clear glass4 ,the glass for this purpose is usually composed of #ec4gj per cent4 of red lead1 #ch4dh per cent4 of pure quartz in fine powder1 preferably water-ground1 and #g4hb per cent4 of carbonate of potash1 the whole coloured when necessary with metallic oxides of a similar nature to the constituents of the natural stones imitated4 ,but for colourless diamonds1 the glass requires no such addition to tint it4 ,from the formula given is made the material known as strass1 or paste1 and stones made of it are mostly exhibited under and amongst brilliant artificial lights4 ,the mere fact that they are sold cheaply is prima facie proof that the stones are glass1 for it is evident that a diamond1 the commercial value of which might be ,l#ej or more1 cannot be purchased for a few shillings and be genuine4 ,so long as this is understood and the stone is sold for the few shillings1 no harm is done2 but to offer it as a genuine stone and at the price of a genuine stone1 would amount to fraud1 and be punishable accordingly4 ,some of these paste1 or white stones1 as they are called in the trade1 are cut and polished exactly like a diamond1 and with such success as occasionally to deceive all but experts4 ,such imitations are costly1 though1 of course1 not approaching the value of the real stones2 it being no uncommon thing for valuable jewels to be duplicated in paste1 whilst the originals are kept in the strong room of a bank or safe-deposit4 ,in all cases1 however1 a hard file will abrade the surface of the false stone4 ,in chapter ,,vii4 we found that quartz is in the seventh degree of hardness1 and an ordinary file is but a shade harder than this1 so that almost all stones higher than ,no4 #g are unaffected by a file unless it is used roughly1 so as to break a sharp edge4 ,in order to prepare artificial diamonds and other stones for the file and various tests1 they are often what is called converted into doublets or triplets4 ,these are made as follows3 the body of the glass is of paste1 and on the table 7see last chapter71 and perhaps on the broader facets1 there will be placed a very thin slab of the real stone1 attached by cement4 ,in the case of the diamond1 the body is clear1 but in the coloured imitations the paste portion is made somewhat lighter in shade than the real stone would be1 the portion below the girdle being coloured chemically1 or mounted in a coloured backing4 ,such a stone will1 of course1 stand most tests1 for the parts usually tested are genuine4 ,a stone of this nature is called a doublet1 and it is evident that when it is tested on the underside1 it will prove too soft1 therefore the triplet has been introduced4 ,this is exactly on the lines of the doublet1 except that the collet and perhaps the pavilions are covered also1 so that the girdle1 which is generally encased by the mounting1 is the only surface-portion of paste4 ,in other cases the whole of the crown is genuine1 whilst often both the upper and lower portions are solid and genuine1 the saving being effected by using a paste centre at the girdle1 covered by the mounting4 ,such a stone as this last mentioned is often difficult to detect without using severe tests and desperate means1 e4g43--7a7 by its crystalline structure 7see ,chapter ,,iii472 7b7 by the cleavage planes 7see ,chapter ,,iv472 7c7 by the polariscope 7see ,chapter ,v472 7d7 by the dichroscope 7see ,chapter ,,vi472 7e7 by specific gravity 7see ,chapter ,,viii472 7f7 cutting off the mounting1 and examining the girdle2 7g7 soaking the stone for a minute or so in a mixture said to have been originally discovered by ,m4 ,d4 ,rothschild1 and composed of hydrofluoric acid and ammonia2 this will not answer for all stones1 but is safe to use for the diamond and a few others4 ,should the jewel be glass1 it will be etched1 if not completely destroyed1 but if genuine1 no change will be apparent2 7h7 soaking the diamond for a few minutes in warm or cold water1 in alcohol1 in chloroform1 or in all these in turn1 when1 if a doublet1 or triplet1 it will tumble to pieces where joined together by the cement1 which will have been dissolved4 ,it is1 however1 seldom necessary to test so far1 for an examination under the microscope1 even with low power1 is usually sufficient to detect in the glass the air-bubbles which are almost inseparable from glass-mixtures1 though they do not detract from the physical properties of the glass4 ,the higher powers of the same instrument will almost always define the junction and the layer or layers of cement1 no matter how delicate a film may have been used4 ,any one of these tests is sufficient to isolate a false stone4 ,some of the softer genuine stones may be fused together with splinters1 dust1 and cuttings of the same stones1 and of this product is formed a larger stone1 which1 though manufactured1 is essentially perfectly real1 possessing exactly the same properties as a naturally formed stone4 ,many such stones are obtained as large as an ordinary pin's head1 and are much used commercially for cluster-work in rings1 brooches1 for watch-jewels1 scarf-pins1 and the like1 and are capable of being cut and polished exactly like an original stone4 ,this is a means of using up to great advantage the lapidary's dust1 and though these products are real stones1 perhaps a little more enriched in colour chemically1 they are much cheaper than a natural stone of the same size and weight4 ,some spurious stones have their colour improved by heat1 by being tinged on the outside1 by being tinted throughout with a fixed colour and placed in a clear setting2 others1 again1 have a setting of a different hue1 so that the reflection of this shall give additional colour and fire to the stone4 ,for instance1 glass diamonds are often set with the whole of the portion below the girdle hidden1 this part of the stone being silvered like a mirror4 ,others are set open1 being held at the girdle only1 the portion covered by the setting being silvered4 ,other glass imitations1 such as the opal1 have a tolerably good representation of the fiery opal given to them by the admixture1 in the glass1 of a little oxide of tin1 which makes it somewhat opalescent1 and in the setting is placed a backing of red1 gold1 copper1 or fiery-coloured tinsel1 whilst the glass itself1 at the back1 is painted very thinly with a paint composed of well washed and dried fish-scales1 reduced to an impalpable powder1 mixed with a little pure1 refined mastic1 or other colourless varnish4 ,this gives a good imitation of phosphorescence1 as well as a slight pearliness1 whilst the tinsel1 seen through the paint and the curious milkiness of the glass1 gives good fire4 ,a knowledge of the colours natural to precious stones and to jewels generally is of great service in their rough classification for testing1 even though some stones are found in a variety of colours4 ,an alphabetical list of the most useful is here appended1 together with their average specific gravities and hardness4 7,see also ,chapter ,,vii4 on ,hardness1 and ,chapter ,,viii4 on ,specific ,gravity47 ,,white ,,or ,,colourless ,,stones4 ,hardness4 ,specific ,gravity4 7,see ,chapter ,,vii47 7,see ,chapter ,,viii47 ,beryl #g-c_/d #b4gji-b4ha ,corundum #i #c4ij-d4af ,diamond #aj #c4ejb-c4efd ,jade #g #c4cjj-c4cha ,opal #e-a_/b-f-a_/b #b4afj-b4bhc ,phenakite #g-c_/d #b4ife ,quartz #g #b4fgj ,rock-crystal #g #b4eba-b4gie ,sapphire #i #d4jdi-d4jfj ,spinel #h #c4fad-c4fed ,topaz #h #c4ejj-c4ebj ,tourmaline #g-a_/d #c4jbi ,zircon #g-a_/b #d4gjj-d4hhj ,,yellow ,,stones4 ,hardness4 ,specific ,gravity4 7,see ,chapter ,,vii47 7,see ,chapter ,,viii47 ,amber #b-a_/b #a4jjj ,beryl #g-c_/d #b4gji-b4haj ,chrysoberyl #h-a_/b #c4fhi-c4geb ,chrysolite #f-g #c4caf-c4ebh ,corundum 7the yellow variety known as ,oriental ,topaz not ,topaz1 see below7 #i #c4ij-d4af ,diamond #aj #c4ejb-c4efd ,garnets 7various7 #f-a_/b-g-a_/b #c4d-d4e ,hyacinth 7a form of ,zircon7 #g-a_/b #d4g-d4hh ,quartz 7,citrine7 #g #b4feh ,sapphire #i #d4jdi-d4jfj ,spinel #h #c4fad-c4fed ,topaz 7for ,oriental ,topaz1 see above7 #h #c4ejj-c4ebj ,tourmaline #g-a_/d #c4baj ,,brown ,,and ,,flame-,,coloured ,,stones4 ,hardness4 ,specific ,gravity4 7,see ,chapter ,,vii47 7,see ,chapter ,,viii47 ,andalusite #g-a_/b #c4bjd ,diamond #aj #c4ejb-c4efd ,garnets 7various7 #f-a_/b-g-a_/b #c4dj-d4ej ,hyacinth 7a form of ,zircon71 see below #g-a_/b #d4gj-d4hh ,quartz 7smoke coloured7 #g #b4fgj ,tourmaline #g-a_/d #c4ajj ,zircon 7,hyacinth7 #g-a_/b #d4gj-d4hh ,,red ,,and ,,rose-,,coloured ,,stones4 ,hardness4 ,specific ,gravity4 7,see ,chapter ,,vii47 7,see ,chapter ,,viii47 ,carnelian 7a variety of ,chalcedony7 #f-a_/b #b4eih-b4faj ,diamond #aj #c4ejb-c4efd ,deep ,red ,garnet #g-a_/d #c4dj-d4ej ,jasper #g #b4ffh ,opal 7the ,fire ,opal7 #e-a_/b-f-a_/b #b4ba 7average7 ,ruby #i #d4jgc-d4jhj ,rhodonite #e-a_/b-f-a_/b #c4dac-c4fag ,sapphire #i #d4jdi-d4jfj ,spinel ,ruby #h #c4fad-c4fed ,topaz #h #c4ejj-c4ebj ,tourmaline #g-a_/d #c4jbd ,zircon #g-a_/b #d4gj-d4hh ,,pink ,,stones4 ,hardness4 ,specific ,gravity4 7,see ,chapter ,,vii47 7,see ,chapter ,,viii47 ,beryl #g-c_/d #b4gji-b4haj ,diamond #aj #c4ejb-c4efd ,ruby #i #d4jgc-d4jhj ,spinel #h #c4fad-c4fed ,topaz 7burnt or pinked71 see ,chapter ,,xiv41 page #ib #h #c4ejj-c4ebj ,tourmaline #g-a_/d #c4jbd ,,blue ,,stones4 ,hardness4 ,specific ,gravity4 7,see ,chapter ,,vii47 7,see ,chapter ,,viii47 ,beryl #g-c_/d #b4gji-b4haj ,diamond #aj #c4ejb-c4efd ,dichorite 7,water ,sapphire7 #g-g-a_/b #d4jdi-d4jfj ,disthene 7,kyanite7 #e-g #c4fji-c4fhh ,iolite 7,cordierite7 #g-a_/d #b4fda ,lapis lazuli #e-a_/b #b4dfa ,sapphire #i #d4jdi-d4jfj ,topaz #h #c4ejj-c4ebj ,tourmaline #g-a_/d #c4afj ,turquoise #f #b4hjj ,,green ,,stones4 ,hardness4 ,specific ,gravity4 7,see ,chapter ,,vii47 7,see ,chapter ,,viii47 ,aquamarine #g-c_/d #b4gja-b4hjj ,chrysoberyl #h-a_/b #c4fhi-c4geb ,chrysolite #f-g #c4caf-c4ebh ,chrysoprase 7,quartz7 #g #b4fgj ,diamond #aj #c4ejb-c4efd ,dioptase #e #c4bhi ,emerald and ,oriental ,emerald #g-c_/d #b4fij ,euclase #g-a_/b #c4jij ,garnet 7see also ,red ,garnet7 #f-a_/b-g-a_/b #c4djj-d4ejj ,heliotrope 7,chalcedony7 #f-a_/b #b4eih-b4faj ,hiddenite 7a variety of ,spodumene7 #f-a_/b-g #c4acj-c4bjj ,jade #g #c4cjj-c4cha ,jadeite #g #c4bii ,malachite #c-a_/b #c4gaj-c4iif ,peridot 7a variety of ,chrysolite7 #f-g #c4caf-c4ebh ,plasma 7a variety of ,chalcedony7 #f-a_/b #b4eih-b4faj ,quartz #g #b4fgj ,sapphire #i #d4jdi-d4jfj ,topaz #h #c4ejj-c4ebj ,tourmaline #g-a_/d #c4adh ,,violet ,,stones4 ,hardness4 ,specific ,gravity4 7,see ,chapter ,,vii47 7,see ,chapter ,,viii47 ,amethyst #g #b4ffa ,diamond #aj #c4ejb-c4efd ,quartz 7,amethyst7 #g #b4fgj ,sapphire #i #d4jdi-d4jfj ,spinel #h #c4fad-c4fed ,tourmaline #g-a_/d #c4afj ,,chatoyant ,,stones4 ,these stones are easily recognisable by their play of colour4 7,see ,chapter ,,xiv47 ,,black ,,stones4 ,hardness4 ,specific ,gravity4 7,see ,chapter ,,vii47 7,see ,chapter ,,viii47 ,diamond #aj #c4ejb-c4efd ,garnet #f-a_/b-g-a_/b #c4djj-d4ejj ,jet #c-a_/b #a4cdh ,onyx 7a variety of ,chalcedony7 #f-a_/b #b4eih-b4faj ,quartz #g #b4fgj ,tourmaline 7not unlike ,black ,resin in appearance7 #g-a_/d #c4jbd-c4cjj ,,chapter ,,xiii4 ,,various ,,precious ,,stones4 ,the ,diamond4 ,to recapitulate certain of the facts respecting the diamond4--,this wonderful gem has the distinction amongst precious stones of being unique2 though many are composed of two1 three1 or but a small number of elements1 the diamond is the only stone known consisting of one element1 and absolutely nothing else--pure crystallised carbon4 ,its hardness is proverbial2 not only is it untouched by the action of a hard file1 but it occasionally refuses to split when struck with finely tempered steel1 which it often causes to break4 ,such was the case with the ,south ,african diamond1 for when the knife that was to break it was struck smartly with a steel bar1 the first blow broke the blade without affecting the diamond1 yet a piece of bort1 or diamond dust1 splinters1 or defective diamonds 7all these being called bort71 may readily be pulverised in a hard steel mortar with a hard steel pestle4 ,the diamond is the hardest stone known2 it is also the only stone known which is really combustible4 ,it is of true adamantine lustre1 classed by experts as midway between the truly metallic and the purely resinous4 ,in refractive power and dispersion of the coloured rays of light1 called its fire1 it stands pre-eminent4 ,it possesses a considerable variety of colour2 that regarded as the most perfect and rare is the blue-white colour4 ,most commonly1 however1 the colours are clear1 with steely-blue casts1 pale and neutral-colour yellow1 whilst amongst the most expensive and rare are those of green1 pale pink1 red1 and any other variety with strong and decided colour4 ,although these stones are sold by the carat1 there can be no hard and fast rule laid down as to the value of a carat1 for this depends on the size1 quality1 and the purity of the stone4 ,the larger the stone the greater the value per carat1 and prices have been known to range from #bel4 per carat for a small stone to #ejjl4 per carat for a large one1 whereas the exceptionally large stones possess a value almost beyond estimation4 ,it often happens that some stones--particularly those from ,south ,africa and ,brazil--are tinted when uncut1 probably by reason of the action upon them of their matrix1 especially if ironstone1 or with rolling for ages amongst ironstone in river-beds1 which gives them a slight metallic appearance2 in each case the cause is suggested by the fact that these tinted stones are usually found in such places1 and that the tinting is very thin and on the surface only1 so that the cutting and shaping of the stone gets below it to the perfectly clear diamond4 ,from ,pliny and other historians we gather that at various periods considerable superstition has existed with regard to diamonds1 such as that if one is powdered it becomes poisonous to a remarkable degree2 that gifts of diamonds between lovers--married and unmarried--produce and seal affection2 hence the popularity of diamonds in betrothal rings4 ,pretty as is this conceit1 there is no doubt about the fact that the gift of diamonds to the object of one's affections does usually produce a feeling of pleasure to both parties1 from which it would appear that there is some ground for the belief4 ,corundum4 ,this mineral is a species of crystal1 or crystalline alumina--an almost pure anhydrous alumina1 ,al#b,o#c--;in many varieties1 both of shape and colour4 ,the chief stone is the ruby1 considered1 when large1 to be of even more importance and value than the diamond4 ,there are many other red stones in this group2 sapphires1 also1 are a species of corundum1 both the blue and the colourless varieties1 as are also the aquamarine1 the emerald1 the amethyst1 the topaz1 and others1 all of widely differing colour1 as well as the star-shaped1 or aster ruby1 called the ruby cat's-eye4 ,all these vary more in colour than in their chemical properties4 ,still another variety1 greyish-black and generally associated with haematite iron ore1 is called emery1 and1 when ground in different degrees of fineness1 is so well known by its general use as a polishing medium as to need no description4 ,it should1 however1 be mentioned that amongst the more coarsely ground emery it is no uncommon thing to find minute sapphires1 taking sapphires in their broad1 commercial meaning1 as signifying any variety of corundum1 except the red and the emery4 ,the surfaces of crystals of corundum are often clouded or dull1 whilst its classification of lustre is vitreous4 ,it is double refracting and has no cleavage4 ,it is found in ,china1 ,india1 ,burma1 ,ceylon1 ,south ,africa1 ,america1 and in many other places1 having a wide distribution4 ,the ,ruby4 ,in the dichroscope the ruby shows two images1 one square of a violet red1 the second square being a truer and a paler red4 ,it may be subjected to strong heat1 when it changes its colour to a sooty or dirty slate1 this varying with the locality in which the stone is found1 and the manner in which the heat is applied4 ,but as it cools it becomes paler and greener1 till it slowly enrichens2 the green first becomes broken1 then warmer1 redder1 and finally assumes its original beautiful blood red4 ,this method of heating is sometimes used as a test1 but it is a test which often means the complete ruin of a stone which is not genuine4 ,another characteristic which1 in the eyes of the expert1 invariably isolates a real from an artificial ruby is its curious mild brilliance1 which as yet has not been reproduced by any scientific method in paste or any other material1 but perhaps the safest test of all is the crystalline structure1 which identical structure appears in no other stone1 though it is possible1 by heating alumina coloured with oxide of iron and perhaps also a trace of oxide of chromium to a very high temperature for a considerable time1 and then cooling very slowly1 to obtain a ruby which is nearly the same in its structure as the real gem2 its specific gravity and hardness may perhaps be to standard1 and when properly cut1 its brilliance would deceive all but an expert4 ,and as in some real rubies there are found slight hollows corresponding or analogous to the bubbles found in melted glass1 it becomes a matter of great difficulty to distinguish the real from the imitation by such tests as hardness1 specific gravity1 dichroism1 and the like1 so that in such a case1 short of risking the ruin of the stone1 ordinary persons are unable to apply any convincing tests4 ,therefore1 only the expert can decide1 by his appreciation of the delicate shade of difference in the light of a true ruby and that of an excellent imitation1 and by the distribution of the colour1 which--however experienced the chemist may be1 or with what care the colouring matter may have been incorporated in the mass--has been found impossible of distribution throughout the body of an artificial stone so perfectly and in the same manner and direction as nature herself distributes it in the genuine4 ,this alone1 even in the closest imitations1 is clear to the eye of the expert1 though not to the untrained eye1 unless the stone is palpably spurious4 ,to one who is accustomed to the examination of precious stones1 however perfect the imitation1 it is but necessary to place it beside or amongst one or more real ones for the false to be almost instantly identified1 and that with certainty4 ,the ,sapphire4 ,the ,sapphire is not so easy to imitate1 as its hardness exceeds that of the ruby1 and imitations containing its known constituents1 or of glass1 are invariably softer than the natural stone4 ,as before remarked1 almost any form of corundum other than red is1 broadly1 called sapphire1 but giving them their strictly correct designations1 we have the olivine corundum1 called chrysolite 7oriental71 which is harder than the ordinary or noble chrysolite1 sometimes called the peridot4 ,the various yellow varieties of corundum take the name of the oriental topaz1 which1 like most1 if not all1 the corundum varieties1 is harder than the gem which bears the same name1 minus the prefix oriental4 ,then we have the amethyst sapphire1 which varies from a red to a blue purple1 being richer in colour than the ordinary amethyst1 which is a form of violet-coloured quartz1 but the corundum variety1 which1 like its companions1 is called the oriental amethyst1 is both rarer and more precious4 ,a very rare and extremely beautiful green variety is called the oriental emerald4 ,the oriental jacinth1 or hyacinth1 is a brown-red corundum1 which is more stable than the ordinary hyacinth1 this latter being a form of zircon2 it changes colour on exposure to light1 which colour is not restored by subsequent retention in darkness4 ,the blue sapphire is of all shades of blue1 from cornflower blue to the very palest tints of this colour1 all the gradations from light to dark purple blues1 and1 in fact1 so many shades of tone and colour that they become almost as numerous as the stones4 ,these stones are usually found in similar situations to those which produce the ruby1 and often along with them4 ,the lighter colours are usually called females1 or feminine stones1 whilst the darker ones are called masculine stones4 ,some of these dark ones are so deep as to be almost black1 when they are called ink sapphires1 and if inclining to blue1 indigo sapphires1 in contradistinction to which the palest of the stones are called water sapphires4 ,the colouring matter is not always even1 but is often spread over the substance of the stone in scabs or splotches1 which rather favours imitation1 and1 where this unevenness occurs1 it may be necessary to cut or divide the stone1 or so to arrange the form of it that the finished stone shall be equally blue throughout4 ,in some cases1 however1 the sapphire may owe its beauty to the presence of two1 three or more colours in separate strata appearing in one stone2 such as a portion being a green-blue1 another a cornflower blue1 another perfectly colourless1 another a pale sky blue1 another yellow1 each perfectly distinct1 the stone being cut so as to show each colour in its full perfection4 ,this stone1 the sapphire1 is hardness ,no4 #i 7see ,hardness table71 and therefore ranks next to the diamond1 which makes it a matter of great difficulty to obtain an imitation which is of the same specific gravity and of the same degree of hardness1 though this has been done4 ,such stones are purchasable1 but though sold as imitations at comparatively low price1 and the buyer may consider them just as good as the real gem1 to the experienced eye they are readily detectable4 ,by heating a sapphire its blue colour slowly fades1 to complete transparency in many cases1 or at any rate to so pale a tint as to pass for a transparent stone4 ,valuable as is the sapphire1 the diamond is more so1 and it follows that if one of these clear or cleared sapphires is cut in the rose or brilliant form--which forms are reserved almost exclusively for the diamond--such a stone would pass very well as a diamond1 and many so cut are sold by unscrupulous people as the more valuable stone1 which fraud an expert would1 of course1 detect4 ,sapphires are mentioned by ,pliny1 and figure largely in the ancient history of ,china1 ,egypt1 ,rome1 etc4 ,the ,greeks dedicated the sapphire specially to ,jupiter1 and many of the stones were cut to represent the god2 it also figured as one of the chief stones worn by the ,jewish ,high ,priest on the breast-plate4 ,some stones have curious rays of variegated colour1 due to their crystalline formation1 taking the shape of a star2 these are called asteriated1 or cat's eye sapphires4 ,others have curious flashes of light1 technically called a play of light 7as described in ,chapter ,,vi4 on ,colour71 together with a curious blue opalescence2 these are the girasol4 ,another interesting variety of this blue sapphire is one known as chatoyant2 this has a rapidly changing lustre1 which seems to undulate between a green-yellow and a luminous blue1 with a phosphorescent glow1 or fire1 something like that seen in the eyes of a cat in the dark1 or the steady1 burning glow observed when the cat is fascinating a bird--hence its name4 ,this is not the same variety as the asteriated1 or cat's eye or lynx eye mentioned above4 ,,chapter ,,xiv4 ,,various ,,precious ,,stones--continued4 ,the ,chrysoberyl4 ,there are certain stones and other minerals which1 owing to their possession of numerous microscopically fine cavities1 of a globular or tubular shape1 have the appearance of rays or stars1 and these are called asteriated4 ,several of such stones have been discussed already in the last chapter1 and in addition to these star-like rays1 some of the stones have1 running through their substance1 one or more streaks1 perhaps of asbestos or calcite1 some being perfectly clear1 whilst others are opalescent4 ,when these streaks pass across the star-like radiations they give the stone the appearance of an eye1 the rays forming the iris1 the clear1 opalescent1 or black streak closely resembling the slit in a cat's eye1 and when these stones are cut en cabochon1 that is1 dome-shaped 7see ,chapter ,,xi4 on ,cutting71 there is nothing to deflect the light beams back and forth from facet to facet1 as in a diamond1 so that the light1 acting directly on these radiations or masses of globular cavities and on the streak1 causes the former to glow like living fire1 and the streak appears to vibrate1 palpitate1 expand1 and contract1 exactly like the slit in the eye of a cat4 ,there are a considerable number of superstitions in connection with these cat's-eye stones1 many people regarding them as mascots1 or with disfavour1 according to their colour4 ,when possessing the favourite hue or fire of the wearer1 such as the fire of the opal for those born in ,october1 of the ruby for those born in ,july1 etc41 these stones are considered to bring nothing but good luck2 to ward off accident1 danger1 and sudden death2 to be a charm against being bitten by animals1 and to be a protection from poison1 the evil eye1 etc4 ,they figured largely1 along with other valuable jewels1 in the worship of the ancient ,egyptians1 and have been found in some of the tombs in ,egypt4 ,they also appeared on the systrum1 which was a sacred instrument used by the ancient ,egyptians in the performance of their religious rites1 particularly in their sacrifices to the goddess ,isis4 ,this1 therefore1 may be considered one of their sacred stones1 whilst there is some analogy between the cat's-eye stones and the sacred cat of the ,egyptians which recurs so often in their hieroglyphics2 it is well known that our domestic cat is not descended from the wild cat1 but from the celebrated cat of ,egypt1 where history records its being domesticated at least thirteen centuries ,b4,c4 ,from there it was taken throughout ,europe1 where it appeared at least a century ,b4,c41 and was kept as a pet in the homes of the wealthy1 though certain writers1 speaking of the mouse-hunters of the old ,romans and ,greeks1 state that these creatures were not the ,egyptian cat1 but a carniverous1 long-bodied animal1 after the shape of a weasel1 called marten1 of the species the beech or common marten 7mustela foina71 found also in ,britain to-day4 ,it is also interesting to note that the various superstitions existing with regard to the different varieties and colours of cats also exist in an identical manner with the corresponding colours of the minerals known as cat's eye4 ,several varieties of cat's-eye have already been described4 ,another important variety is that of the chrysoberyl called cymophane4 ,this is composed of glucina1 which is glucinum oxide1 or beryllia1 ,be,o1 of which there is #ai4h per cent41 and alumina1 or aluminium oxide1 ,al#b,o#c1 of which there is #hj4b per cent4 ,it has1 therefore1 the chemical formula1 ,be,o1,al#b,o#c4 ,this stone shows positive electricity when rubbed1 and1 unlike the sapphires described in the last chapter1 which lose their colour when heated1 this variety of chrysoberyl shows no change in colour1 and any electricity given to it1 either by friction or heat1 is retained for a long time4 ,when heated in the blowpipe alone it remains unaltered1 that is1 it is not fusible1 and even with microcosmic salt it requires a considerably long and fierce heat before it yields and fuses1 and acids do not act upon it4 ,it crystallises in the #dth 7rhombic7 system1 and its lustre is vitreous4 ,the cymophane shows a number of varieties1 quite as many as the chrysoberyl1 of which it is itself a variety1 and these go through the gamut of greens1 from a pale white green to the stronger green of asparagus1 and through both the grey and yellow greens to dark4 ,it is found in ,ceylon1 ,moravia1 the ,ural ,mountains1 ,brazil1 ,north ,america1 and elsewhere4 ,the cat's-eye of this is very similar to the quartz cat's-eye1 but a comparison will make the difference so clear that they could never be mistaken1 apart from the fact that the quartz has a specific gravity considerably lower than the chrysoberyl cat's-eye1 which latter is the true cat's-eye1 and the one usually understood when allusion is made to the stone without any distinguishing prefix1 such as the ruby1 sapphire1 quartz1 etc41 cat's eye4 ,it should1 however1 be mentioned that this stone is referred to when the names ,ceylonese and ,oriental cat's-eye are given1 which names are used in the trade as well as the simple appellation1 cat's eye4 ,one peculiarity of some of these stones is that the fire or glow is usually altered in colour by the colour of the light under which it is seen1 the change of colour being generally the complementary4 ,thus1 a stone which in one light shows red1 in another will be green2 the eye showing blue in one light will become orange in another2 whilst the yellow of another stone may show a decided purple or amethyst in a different light4 ,a good test for this1 and indeed most precious stones1 is that they conduct heat more quickly than does glass1 and with such rapidity that on breathing upon a stone the warmth is conducted instantly1 so that1 though the stone is dimmed the dimness vanishes at once1 whereas with glass the film of moisture fades but slowly in comparison4 ,the ,topaz4 ,the name topaz is derived from the ,greek topazos1 which is the name of a small island situated in the ,gulf of ,arabia1 from whence the ,romans obtained a mineral which they called topazos and topazion1 which mineral to-day is termed chrysolite4 ,the mineral topaz is found in ,cornwall and in the ,british ,isles generally2 also in ,siberia1 ,india1 ,south ,america and many other localities1 some of the finest stones coming from ,saxony1 ,bohemia1 and ,brazil1 especially the last-named4 ,the cleavage is perfect and parallel to the basal plane4 ,it crystallises in the #dth 7rhombic7 system2 in lustre it is vitreous2 it is transparent1 or ranging from that to translucent2 the streak is white or colourless4 ,its colour varies very much--some stones are straw-colour1 some are grey1 white1 blue1 green1 and orange4 ,a very favourite colour is the pink1 but in most cases this colour is not natural to the stone1 but is the result of burning1 or pinking as the process is called technically1 which process is to raise the temperature of a yellow stone till the yellow tint turns to a pink of the colour desired4 ,the topaz is harder than quartz1 as will be seen on reference to the ,hardness table1 and is composed of a silicate of aluminium1 fluorine taking the place of some of the oxygen4 ,its composition averages #af4be per cent4 of silica1 #ee4ge per cent4 of alumina1 or oxide of aluminium1 and fluoride of silicium1 #bh per cent4 ,its formula is ,al7,f1,,oh7#b ,si,o#d1 or 7,al,f7#b,si,o#d4 ,from this it will be understood that the fluorine will be evolved when the stone is fused4 ,it is1 however1 very difficult to fuse1 and alone it is infusible under the blowpipe1 but with microcosmic salt it fuses and evolves fluorine1 and the glass of the tube in the open end of which the stone is fixed is bitten with the gas4 ,such experiments with the topaz are highly interesting1 and if we take a little of the powdered stone and mix with it a small portion of the microcosmic salt1 we may apply the usual test for analysing and proving aluminium1 thus3 a strongly brilliant mass is seen when hot1 and if we moisten the powder with nitrate of cobalt and heat again1 this time in the inner flame1 the mass becomes blue4 ,other phenomena are seen during the influence of heat4 ,some stones1 as stated1 become pink on heating1 but if the heating is continued too long1 or too strongly1 the stone is decoloured4 ,others1 again1 suffer no change1 and this has led to a slight difference of opinion amongst chemists as to whether the colour is due to inorganic or organic matter4 ,heating also produces electricity1 and the stone1 and even splinters of it1 will give out a curious phosphorescent light1 which is sometimes yellow1 sometimes blue1 or green4 ,friction or pressure produces strong electrification2 thus the stones may be electrified by shaking a few together in a bag1 or by the tumbling of the powdered stone-grains over each other as they roll down a short inclined plane4 ,the stones are usually found in the primitive rocks1 varying somewhat in different localities in their colour2 many of the ,brazilian stones1 when cut as diamonds1 are not unlike them4 ,in testing1 besides those qualities already enumerated1 the crystalline structure is specially perfect and unmistakable4 ,it is doubly refractive1 whereas spinel and the diamond1 which two it closely resembles1 are singly refractive4 ,topaz is readily electrified1 and1 if perfect at terminals1 becomes polarised2 also the commercial solution of violets1 of which a drop only need be taken for test1 is turned green by adding to it a few grains of topaz dust1 or of a little splinter crushed to fine powder4 ,the ,beryl4 ,the beryl is a compound of silicates of beryllia and alumina1 with the formula #c;,be,o,si,o#b ,al#b,o#c1c,si,o#b1 or #c;,be,o1,al#b,o#c1f,si,o#b4 ,it differs very little indeed from the emerald1 with the exception of its colour4 ,in the ordinary varieties this is somewhat poor1 being mostly blue1 or a dirty or a greenish yellow2 the better kinds1 however1 possess magnificent colour and variety1 such as in the aquamarine1 emerald1 etc4 ,the cleavage is parallel to the basal plane4 ,its lustre is sometimes resinous1 sometimes vitreous1 and it crystallises in the #bnd 7hexagonal7 system4 ,it occurs in somewhat long1 hexagonal prisms1 with smooth1 truncated planes1 and is often found in granite and the silt brought down by rivers from granite1 gneiss1 and similar rocks4 ,it is found in ,great ,britain and in many parts of ,europe1 ,asia1 and ,america1 in crystals of all sizes1 from small to the weight of several tons4 ,the common kinds are too opaque and colourless to be used as gems and are somewhat difficult of fusion under the blowpipe1 on the application of which heat some stones lose their colour altogether1 others partly2 others1 which before heating were somewhat transparent1 become clouded and opaque2 others suffer no change in colour1 whilst some are improved4 ,in almost every case a slight fusion is seen on the sharp edges of fractures1 which become smooth1 lose their sharpness1 and have the appearance of partly fused glass4 ,the hardness varies from #g-a_/d to #h1 the crystals being very brittle1 breaking with a fracture of great unevenness4 ,the better varieties are transparent1 varying from that to translucent1 and are called the noble beryls4 ,transparent beryl crystals are used by fortune-tellers as gazing stones1 in which they claim to see visions of future events4 ,the ,emerald4 ,considering the particular emerald which is a variety of beryl--although the name emerald in the trade is applied somewhat loosely to any stone which is of the same colour1 or approaching the colour of the beryl variety--this emerald only differs chemically from the beryl1 just described1 in possessing an addition of oxide of chromium4 ,in shape1 crystallisation1 fracture and hardness1 it is the same1 and often contains1 in addition to the chromium1 the further addition of traces of carbonate of lime1 magnesia1 and occasionally faint traces of hornblende and mica1 which evidently result from its intimate association with the granite rock and gneiss1 amongst which it is mostly found1 the latter rocks being of a slaty nature1 in layers or plates1 and1 like granite1 containing mica1 pyrites1 felspar1 quartz1 etc4 ,emeralds have been known from very early times1 and are supposed to have been found first in the mines of ancient ,egypt4 ,they were considered amongst the rarest and the most costly of gems1 and it was the custom1 when conferring lavish honour1 to engrave or model emeralds for presentation purposes4 ,thus we find ,pliny describes ,ptolemy giving ,lucullus1 on his landing at ,alexandria1 an emerald on which was engraved his portrait4 ,pliny also relates how the short-sighted ,nero watched the fights of gladiators through an eye-glass made of an emerald1 and in ancient times1 in ,rome1 ,greece1 and ,egypt1 eye-glasses made of emeralds were much valued4 ,many of these1 as well as engraved and carved emeralds1 have been discovered in ruins and tombs of those periods4 ,the copper emerald is rare2 it is a hydrous form of copper silicate1 ,cu,o,si,o#b ,h#b,o1 of a beautiful emerald green1 varying from transparent to translucent4 ,it exhibits double refraction1 and is a crystallised mineral1 brittle1 and showing a green streak4 ,this is less hard than the real emerald1 is heavier1 deeper in colour1 and is usually found in crystals1 in cavities of a particular kind of limestone which exists at ,altyn-,tuebe1 a hill in the ,altai ,mountains1 in the ,urals1 and in ,north and ,central ,america4 ,the ,tourmaline4 ,the tourmaline is a most complex substance2 almost every stone obtained has a different composition1 some varying but slightly1 with mere traces of certain constituents which other stones possess in a perceptible degree4 ,consequently1 it is not possible to give the chemical formula1 which might1 and possibly would1 be found but seldom1 even in analyses of many specimens4 ,it will therefore be sufficient to state the average composition1 which is3--ferrous oxide1 manganous oxide1 potash1 lime1 boracic acid1 magnesia1 soda1 lithia1 and water4 ,these form1 roughly speaking1 #be per cent4 of the bulk1 the remainder being oxide of silicon and oxide of aluminium in about equal parts4 ,it crystallises in the #bnd 7hexagonal7 system1 with difficult cleavage and vitreous lustre4 ,it will naturally be expected that a substance of such complexity and variety of composition must necessarily have a corresponding variety of colour2 thus we find in this1 as in the corundum1 a wonderful range of tints4 ,the common is the black1 which is not used as a gem4 ,next come the colourless specimens1 which are not often cut and polished1 whereas all the transparent and coloured varieties are in great demand4 ,to describe adequately their characteristics with relation to light would alone require the space of a complete volume1 and the reader is referred to the many excellent works on physics 7optics7 which are obtainable4 ,this stone is doubly refracting1 exhibiting extremely strong dichroism1 especially in the blue and the green varieties4 ,it polarises light1 and when viewed with the dichroscope shows a remarkable variety of twin colours4 ,it will be remembered that in ,hogarth's ,rake's ,progress1 the youth is too engrossed in the changing wonders of a tourmaline to notice the entrance of the officers come to arrest him4 ,,chapter ,,xv4 ,,various ,,precious ,,stones--continued4 ,zircon4 ,zircon appears to have been first discovered by ,klaproth in #aghi1 in the form of an earth1 and six years later he found that the stone hyacinth contained a similar substance1 both having the formula1 ,zr,si,o#d1 and both having as their colouring agent ferric oxide4 ,there are several methods of obtaining the metallic element1 zirconium2 it is however with the silicate of zirconium that we have to deal at the moment4 ,this is called zircon1 ,zr,si,o#d1 or hyacinth when transparent or red1 but when smoke-coloured1 or colourless1 it is the jargoon1 or jarcon1 and is found in silt and alluvial soils1 limestone1 gneiss1 and various forms of schist1 in ,india1 ,australia1 the ,urals1 and certain parts of ,america4 ,it is often combined with and found in juxtaposition to gold and certain varieties of precious stones4 ,the lines of cleavage are parallel to the sides of the prism1 and the crystals have an adamantine1 or diamond lustre1 varying from the completely opaque to the transparent4 ,in some varieties the oxide of uranium is also present in traces4 ,it crystallises in the #crd 7tetragonal7 system1 with indistinct cleavage4 ,its specific gravity varies from #d4gj to #d4hh1 according to the specimen and the locality4 ,this stone1 like some of the others described1 has a very wide range of colour1 going through reds1 browns1 greens1 yellows1 oranges1 whites1 greys1 blues from light to indigo1 notwithstanding which it is somewhat difficult to imitate scientifically1 though its composition of #cc per cent4 of silica with #fg per cent4 of zirconia 7the oxide of zirconium71 is practically all it contains1 apart from the colouring matter1 such as the metallic oxides of iron1 uranium1 etc4 ,its hardness is #g-a_/b1 consequently it is untouched by a file1 and so far1 if one or perhaps two of the three qualities of colour1 hardness1 and specific gravity1 are obtained in a chemically made zircon1 the third is wanting4 ,under the blowpipe1 zircons are infusible1 but the coloured stones when heated strongly become heavier1 and as they are contracting1 their colour fades1 sometimes entirely1 which changes are permanent1 so that as they possess the adamantine lustre1 they are occasionally cut like a diamond1 and used as such1 though their deficiency in fire and hardness1 and their high specific gravity1 make them readily distinguishable from the diamond4 ,on exposure to light the coloured zircon becomes more or less decoloured2 especially is this so in sunlight1 for when the direct rays of the sun fall upon it1 the colours fade1 and for a moment or two occasional phosphorescence follows1 as is the case when the stone is warmed or heated in a dark room4 ,the stone appears to be very susceptible to brilliant light-rays1 and in certain specimens which were split for testing1 one half of each being kept excluded from light for purposes of comparison1 it was found that sunshine affected them most2 then brilliant acetylene gas1 which was more effective still when tinted yellow by being passed through yellow glass4 ,the electric arc was not so effective1 but the electric light of the mercury-vapour lamp1 though causing little change at the first1 after a few hours' exposure rapidly bleached certain of the colours1 whilst having no effect on others4 ,coal gas with incandescent fibre mantle was slightly effective1 whilst the coal-gas1 burned direct through an ordinary burner1 affected very few of the colours1 even after twenty-four hours' exposure at a distance of three feet4 ,in all these cases1 though the colours were slightly improved by the stones being kept for a time in the dark1 they failed to recover their original strength1 showing permanent loss of colour4 ,the ,silicates4 ,the chief of these are the garnets1 crystallising in the cubic system1 and anhydrous4 ,the garnet is usually in the form of a rhombic dodecahedron1 or as a trisoctahedron 7called also sometimes an icosatetrahedron71 or a mixture of the two1 though the stones appear in other cubic forms4 ,in hardness they vary from #f-a_/b to #h-a_/b4 ,they average from #dj to about #db per cent4 of silica1 the other ingredients being in fairly constant and definite proportions4 ,they are vitreous and resinous in their lustre and of great variety of colour1 chiefly amongst reds1 purples1 violets1 greens1 yellows and blacks1 according to the colouring matter present in their mass4 ,there are many varieties which are named in accordance with one or more of their constituents1 the best known being3 7,a7 ,the iron-alumina garnet1 having the formula #f;,fe,o1 #c,si,o#b #b;,al#b,o#c1 #c,si,o#b4 ,this is the precious garnet1 or almandine1 sometimes called the ,oriental garnet2 these stones are found in ,great ,britain1 ,india1 and ,south ,america1 and are deep red and transparent1 of vitreous lustre4 ,they get up well1 but certain varieties are so subject to defects in their substance1 brought about by pressure1 volcanic action1 and other causes1 some of which are not yet known1 that their quality often becomes much depreciated in consequence4 ,this inferior variety of the iron-alumina garnet is called the common garnet1 and has little lustre1 being sometimes opaque4 ,the perfect qualities1 or almandine1 as described above1 are favourite stones with jewellers1 who mount great quantities of them4 ,the second variety is the 7,b7 lime-iron garnet1 formula1 #f;,ca,o1#c,si,o#b #b;,fe#b,o#c1c,si,o#b4 ,the chief of this class is the melanite1 sometimes dull1 yet often vitreous2 it is mostly found in volcanic rocks1 such as tuff2 this variety is very popular with jewellers for mourning ornaments1 for as it is a beautiful velvet-black in colour and quite opaque1 it is pre-eminent for this purpose1 being considerably less brittle than jet1 though heavier4 ,another variety is the topazolite1 both yellow and green4 ,the aplome is greenish-yellow1 yellowish-green1 brown1 and usually opaque4 ,a further form of lime-iron garnet is the pyreneite1 first found in the ,pyrenees ,mountains1 hence its name4 ,the 7,c7 lime-chrome garnets--#f;,ca,o1#c,si,o#b #b;,cr#b,o#c1 #c,si,o#b--the chief of which is uwarowite4 ,this is of a magnificent emerald green colour1 translucent at edges and of a vitreous lustre4 ,when heated on the borax bead it gives an equally beautiful green1 which is1 however1 rather more inclined to chrome than emerald4 ,this is an extremely rare stone in fine colour1 though cloudy and imperfect specimens are often met with1 but seldom are large stones found without flaws and of the pure colour1 which rivals that of the emerald in beauty4 ,the fourth variety 7,d7 is the lime-alumina garnet1 its formula being--#f;,ca,o1#c,si,o#b #b;,al#b,o#c1c,si,o#b4 ,like the others1 it has a number of sub-varieties1 the chief being the cinnamon stone1 which is one of great beauty and value when perfect4 ,this stone is almost always transparent when pure1 which property is usually taken as one of the tests of its value1 for the slightest admixture or presence of other substances cloud it1 probably to opacity1 in accordance with the quantity of impurity existent4 ,this variety is composed of the oxides of aluminium and silicon with lime4 ,in colour it ranges from a beautiful yellowish-orange deepening towards the red to a pure and beautiful red4 ,romanzovite is another beautiful variety1 the colour of which ranges through browns to black4 ,another important variety is the succinite1 which gets up well and is a favourite with jewellers because of its beautiful1 amber-like colour1 without possessing any of the drawbacks of amber4 7,e7 ,the magnesia-alumina garnet--#f,mg,o1#c,si,o#b #b;,al#b,o#c1c,si,o#b--;is somewhat rare1 the most frequently found being of a strong crimson colour and transparent4 ,this variety is called pyrope1 the deeper and richer tints being designated carbuncle1 from the ,latin carbunculus1 a little coal1 because when this beautiful variety of the noble garnet is held up between the eyes and the sun1 it is no longer a deep1 blood-red1 but has exactly the appearance of a small piece of live or glowing coal1 the scarlet portion of its colour-mixture being particularly evident4 ,the ancient ,greeks called it anthrax1 which name is sometimes used in medicine to-day with reference to the severe boil-like inflammation which1 from its burning and redness1 is called a carbuncle1 though it is more usual to apply the word anthrax to the malignant cattle-disease which is occasionally passed on to man by means of wool1 hair1 blood-clots1 etc41 etc41 and almost always ends fatally4 ,a great deal of mystery and superstition has always existed in connexion with this stone--the invisibility of the bearer of the egg-carbuncle laid by a goldfinch1 for instance4 7,f7 ,the manganese-alumina garnet--#f,mn,o1#c,si,o#b #b;,al#b,o#c1c,si,o#b--;is usually found in a crystalline or granular form1 and mostly in granite and in the interstices of the plates1 or laminae1 of rocks called schist4 ,one variety of this1 which is a deep hyacinth in colour1 though often of a brown-tinted red1 is called spessartine1 or spessartite1 from the district in which it is chiefly found1 though its distribution is a fairly wide one4 ,the ,lapis-,lazuli4 ,the lapis-lazuli1 sometimes called azure stone1 is almost always blue1 though often containing streaks of white and gold colour1 the latter of which are due to the presence of minute specks or veins of iron pyrites1 the former and colourless streaks being due to free lime1 calcite1 and other substances which have become more or less blended with the blue colour of the stone4 ,it has a vitreous lustre1 crystallises in the #ast1 or cubic system1 and is a complex substance1 varying considerably in its ingredients in accordance with the locality in which it is found1 its matrix1 and the general geological formation of the surrounding substances1 which may1 by the penetration of moisture1 be brought to bear upon the stone1 thus influencing to a great extent its chemical composition4 ,so that we find the stone composed of about a quarter of its substance of alumina1 or oxide of aluminium1 silica to the extent of almost half1 the remainder being lime1 soda1 sulphur1 and occasionally traces of copper and iron4 ,it is mostly found in granite and certain crystalline limestone rocks1 in fairly large masses4 ,it is of great antiquity1 figuring extensively in ancient ,egyptian history1 both in its form as a stone and ground up into a pigment for the decoration of sacred and royal vessels and appointments4 ,when so ground1 it forms the stable and magnificent colour1 genuine ultramarine1 which is the finest and purest blue on the artist's palette1 but owing to its extremely high price its use is not in very great demand1 especially as many excellent chemical substitutes of equal permanence are obtainable at little cost4 ,the ,turquoise4 ,the turquoise is a pseudomorph 7see ,chapter ,,iv41 ,cleavage47 ,in colour it is blue or greenish-blue1 sometimes opaque1 varying between that and feeble translucency1 though it should be said that in all forms1 even those considered opaque1 a thin cutting of the stone appears almost transparent1 so that the usual classing of it among the opaque stones must be done with this reservation4 ,in composition it contains about #bj per cent4 of water1 about a third of its substance being phosphoric acid1 or phosphorus-pentoxide2 sometimes nearly half of it is alumina1 with small quantities of iron in the form of variously coloured oxides1 with oxide of manganese4 ,the great proportion of water1 which it seems to take up during formation1 is mostly obtained in the cavities of weathered and moisture-decomposing rocks4 ,its average formula may be said to be ,al#b,o#c,p#b,o#e #e;,h#b,o1 and sometimes ,al#b,o#c ,fe,o,p#b,o#e #e;,h#b,o4 ,it must therefore follow that when the stone is heated1 this water will separate and be given off in steam1 which is found to be the case4 ,the water comes off rapidly1 the colour of the stone altering meanwhile from its blue or blue-green to brown4 ,if the heat is continued sufficiently long1 this brown will deepen to black1 while the flame is turned green4 ,this is one of the tests for turquoise1 but as the stone is destroyed in the process1 the experiment should be made on a splinter from it4 ,this stone is of very ancient origin1 and many old turquoise deposits1 now empty1 have been discovered in various places4 ,history records a magnificent turquoise being offered in ,russia for about ,l#hjj a few centuries ago1 which is a very high price for these comparatively common stones4 ,owing to the presence of phosphorus in bones1 it is not uncommon to find1 in certain caves which have been the resort of wild animals1 or into which animals have fallen1 that bones in time become subjected to the oozing and moisture of their surroundings2 alumina1 as well as the oxides of copper1 manganese and iron1 are often washed across and over these bones lying on the cave floor1 so that in time1 this silt acts on the substance of the bones1 forming a variety of turquoise of exactly the same composition as that just described1 and of the same colour4 ,so that around the bones there eventually appears a beautiful turquoise casing2 the bone centre is also coloured like its casing1 though not entirely losing its bony characteristics1 so that it really forms a kind of ossified turquoise1 surrounded by real turquoise1 and this is called the bone turquoise or odontolite4 ,,index ,adamantine lustre1 #bh glimmering1 #bi glinting1 or glistening1 #bi lustreless1 #bi shining1 #bi splendent1 #bi ,agate1 #aa ,almandine1 #aja ,amethyst1 #aa oriental1 #he sapphire1 #he ,amorphous stones and their characteristics1 #bc ,analysis1 #e ,aplome1 #aja ,asters1 or asteriated stones1 #hb1 #hg-ia ,azure-stone1 #ajc ,beryl1 #aj1 #id colours of1 in dichroscope1 #cd ,beryllium1 #aj ,bezils1 #ff ,black stones1 list of1 #gi ,blue sapphire1 composition of the1 #aj stones1 list of1 #gg ,bone-turquoise1 #ajf ,break1 as opposed to cleavage1 #ai ,brilliant-cut stones1 #ff ,brown stones1 list of1 #gf ,building up of crystals1 #ac ,burnt1 or pinked topaz1 #ib ,cabochon-cut stones1 #fd 7the double71 #fe 7the hollow71 #fe ,carbonate series1 #aa ,carbuncle1 #ajb1 #ajc ,cat of ,egypt1 #hi ,cat's eye stones1 #hb1 #hg-ia list of 7see ,chatoyant ,stones71 #gh ,ceylonese cat's eye 7see ,cat's eye7 ,change of colour 7not to be confused with ,play of colour and ,opalescence1 which see2 see also ,fire71 #cf ,characteristics of precious stones1 #a1 #c ,chatoyant stones1 list of1 #gh ,chemical illustration of formation of precious stones1 #h ,chloride of palladium in dichroscope1 #cd ,chrysoberyl1 #hh ,chrysolite1 #aa ordinary1 or noble1 #he oriental1 #he ,cinnamon stone1 #ajb ,claims of precious stones1 #d ,cleavage affecting tests1 #dc and cleavage as opposed to break1 #ai1 #bb ,colour1 #bf1 #bh1 #cj1 #cb ,colourless stones1 list of1 #ge ,colours and characteristics of the various opals1 #ce1 #cf of precious stones1 list of1 #ge-gi ,common garnet1 #aja opal1 #ce ,composite crystals1 #ac ,composition of paste1 or strass1 for imitation stones1 #ga ,composition of precious stones1 #g ,converted stones1 #gb ,corundum1 #hb ,crown portion of stones1 #fe1 #ff ,crystalline structure1 physical properties1 of #ac ,crystallography1 #ad ,crystals1 axes of symmetry1 #ae groups of1 #ae1 #af planes of symmetry1 #ae systems of1 #af 7#a7 ,cubic--isometric1 monometric1 regular1 #af 7#b7 ,hexagonal--rhombohedral1 #af 7#c7 ,tetragonal--quadratic1 square prismatic1 dimetric1 pyramidal1 #af 7#d7 ,rhombic--orthorhombic1 prismatic1 trimetric1 #af 7#e7 ,monoclinic--clinorhombic1 monosymmetric1 oblique1 #af1 #ag 7#f7 ,triclinic--anorthic1 asymmetric1 #af1 #ag treatment of1 #ad ,culasse portion of stones1 #ff ,cullinan diamond 7see also ,stars of ,africa71 #bb1 #fd1 #fh1 #hj ,cutting of precious stones1 #c1 #d1 #fb ,cymophane1 #ij ,definition of a precious stone1 #a ,diamond1 characteristics of the1 #hj composition of the1 #aj 7sapphire71 #hf unique1 #aj 7zircon71 #ii ,diaphaneity1 #bf1 #bh ,diaphanous stones1 #bh ,dichroscope1 #cc how to make a1 #cc how to use a1 #cd ,dimorphism in precious stones1 #be ,double cabochon-cut stones1 #fe refraction 7see ,refraction7 ,doublets1 #gb ,electric and magnetic influences1 #eg experiments with precious stones and pithball and electroscope1 #eg experiments with tourmaline1 #eh1 #ei ,emerald1 #aj1 #aa1 #ie1 #if oriental1 #he ,en cabochon-cut stones1 #fd ,experiments to show electric polarity1 #eh1 #ei ,facets in stones1 description of the1 #fg1 #fh ,feminine stones1 #he ,fire in stones 7see also ,change of ,colour1 ,opalescence1 and ,play of ,colour71 #cf1 #cg ,fire opal1 #ce ,flame-coloured stones1 list of1 #gf ,flaws1 #fc ,formation of precious stones1 #e1 #h chemical illustration of1 #h1 #i ,garnet1 #aa1 #ajj ,garnets 7,a7 iron-alumina 7called also almandine and precious or oriental garnet71 #aja sub-variety1 common garnet1 #aja 7,b7 lime-iron1 #aja sub-variety aplome1 #aja melanite1 #aja pyreneite1 #aja topazolite1 #aja 7,c7 lime-chrome1 #aja1 #ajb sub-variety uwarowite1 #aja1 #ajb 7,d7 lime-alumina1 #ajb sub-variety cinnamon stone1 #ajb romanzovite1 #ajb succinite1 #ajb 7,e7 magnesia-alumina1 #ajb1 #ajc sub-variety carbuncle1 or anthrax1 #ajb1 #ajc noble1 #ajc pyrope1 #ajb 7,f7 manganese-alumina1 #ajc sub-variety spessartine1 or spessartite1 #ajc ,girdle portion of a stone1 #ff ,glimmering1 in lustre1 definition of1 #bi ,glinting1 or glistening in lustre1 definition of1 #bi ,goutte de suif-cut stones1 #fe ,great ,mogul diamond1 #fd ,green stones1 list of1 #gh ,groups of crystals 7see ,crystals7 ,hardness1 physical properties of1 #ci table of1 #ci1 #dj1 #da ,heat indexes1 #ed physical properties of1 #eb ,hollow-cabochon1 #fe ,hyacinth1 ordinary 7a form of zircon71 #he1 #ih oriental1 #he ,hyalite 7opal71 #ce ,hydrophane 7opal71 #ce ,imitations and tests of precious stones1 #gj ,indigo sapphires1 #hf ,ink sapphires1 #he ,iridescence1 and cause of1 #cg1 #ch ,iron-alumina garnets1 #aja ,jacinth1 oriental1 #he ,jarcon1 or jargoon1 #ih ,koh-i-nur1 #fd ,lapis-lazuli1 #ajc ,light1 physical properties of1 #bf ,lime-alumina garnets1 #ajb cinnamon stone1 #ajb romanzovite1 #ajb succinite1 #ajb ,lime-chrome garnets1 #aja1 #ajb uwarowite1 #aja1 #ajb ,lime-iron garnets1 #aja aplome1 #aja pyreneite1 #aja topazolite1 #aja ,list of stones according to colour1 #ge-gi hardness1 #ci-da specific gravity1 #dh-ej ,lustre1 #bf1 #bh ,lustreless1 definition of1 #bi ,lynx-eye stones1 #hg ,magnesia-alumina garnets1 #ajb1 #ajc carbuncle1 or anthrax1 #ajb noble1 #ajc pyrope1 #ajb ,magnetic and electric influences1 #eg-fa ,malachite1 #aa ,manganese-alumina garnets1 #ajc spessartine1 or spessartite1 #ajc ,masculine stones1 #he ,melanite1 #aja ,menilite 7opal71 #cf ,metallic-lustre stones1 #bh1 #bi ,mohs's table of hardness1 #ci-da ,noble garnet1 #ajc or precious opal1 #ce ,non-diaphanous stones1 #bh ,odontolite1 #ajf ,olivine corundum 7see ,chrysolite71 #he ,opal1 #aa varieties of1 #ce1 #cf ,opalescence 7not to be confused with ,change of ,colour and ,play of ,colour1 which see2 see also ,fire71 #cf1 #cg ,oriental amethyst1 #he cat's eye 7see ,cat's eye7 emerald1 #he garnet1 #aja topaz1 #he ,origin of precious stones1 #g ,paste1 or strass1 for imitation stones1 composition of1 #ga ,pavilion portion of cut stones1 #ff ,pearly-lustre stones1 #bh1 #bi ,peridot 7see ,noble ,chrysolite71 #he ,pink-coloured stones1 list of 7see also ,red71 #gg ,pinked topaz1 #ib ,phosphorescence1 #bf1 #cj ,physical properties3-- ,a4--,crystalline structure1 #ac ,b4--,cleavage1 #ai ,c4--,light1 #bf ,d4--,colour1 #cb ,e4--,hardness1 #ci ,f4--,specific gravity1 #de ,g4--,heat1 #eb ,h4--,magnetic and electric influences1 #eg ,play of colour 7not to be confused with ,change of ,colour and ,opalescence1 which see2 see also ,fire71 #cf1 #cg ,pleochroism1 #cc ,polarisation1 electric1 #eh1 #ei of light1 #bf1 #bg ,polariscope1 #bg1 #bh ,polishing precious stones1 #c1 #d ,polymorphism in precious stones1 #be ,precious1 or noble opal1 #ce ,pseudomorphism in precious stones1 #bc1 #bd ,pyreneite1 #aja ,pyro-electricity1 development and behaviour of1 #eh-fj ,pyrope1 #ajb ,qualities of precious stones1 #a1 #c ,red and rose-coloured stones1 list of 7see also ,pink71 #gf1 #gg ,reflection of light1 #bf1 #bh ,refraction of heat1 #eb-ee light1 #bf1 #bg ,reproduction of crystalline form1 #bj1 #ba ,resinous lustre stones1 #bh1 #bi ,rock-crystal1 #aa ,romanzovite1 #ajb ,rose-coloured stones 7see ,red1 above71 #gf1 #gg ,rose1 or rosette-cut stones1 #fe ,rothschild's testing solution1 #gc ,ruby1 characteristics of1 #hc composition of1 #aj ,sapphire1 amethyst1 #he and its varieties1 #hd1 #he cleared1 #hf diamonds1 #hg indigo1 #hf ink1 #he the blue1 composition of1 #aj1 #he water1 #hf ,semi-diaphanous stones1 #bh ,shining1 in lustre1 definition of1 #bi ,silica group1 composition of the1 #aa ,silicates1 #ajj ,silky-lustre stones1 #bh1 #bi ,single-refraction 7see ,refraction7 ,south ,african diamond 7see ,cullinan ,diamond7 ,specific gravity1 #de ,splendent1 in lustre1 definition of1 #bi ,splitting of the ,cullinan diamond1 #bb ,star-portion of stones1 #fe ,stars of ,africa 7see also ,cullinan ,diamond71 #bb1 #fd1 #fh ,starting or splitting of stones on cleavage planes1 #bc ,step-cut stones1 #ff ,stones arranged according to colour1 #ge-gi hardness1 #ci-da specific gravity1 #dh-ej ,strass for imitation stones1 composition of1 #ga ,sub-metallic in lustre1 definition of1 #bi ,sub-translucent stones1 #bh ,sub-transparent stones1 #bh ,succinite1 #ajb ,synthesis1 #e ,systems of crystals 7see ,crystals7 ,table-cut stones1 #fe ,tallow drops1 #fe ,teeth of stone1 #fe ,testing by crystalline structure1 #ag hardness1 #dj1 #dc with needles1 #da gems by dichroscope1 #cc1 #cd solution 7,rothschild's71 #gc ,tests of precious stones 7general71 #gj ,topaz1 #aa1 #ia colours of1 in dichroscope1 #cd oriental1 #he ,topazolite1 #aja ,tourmaline1 #if1 #ig electric experiments with1 #eh1 #ei ,translucent stones1 #bh ,transmission of heat1 #eb-ef light1 #bf ,transparent stones1 #bh ,trap-cut stones1 #ff ,tri-morphism in precious stones1 #be ,triplets1 #gb ,turquoise1 #ajd 7bone71 #ajf composition of the1 #aa odontolite1 #ajf ,uwarowite1 #aja1 #ajb ,violet stones1 list of1 #gh ,vitreous-lustre stones1 #bh1 #bi ,water-sapphires1 #hf ,white 7paste7 stones1 #ga stones1 list of1 #ge ,yellow stones1 list of1 #gf topaz1 #ib ,zircon1 #aj1 #ih diamonds1 #ii ,zirconium1 #aj ,,london3 ,,printed ,,by ,,william ,,clowes ,,and ,,sons1 ,,limited1 ,,great ,,windmill ,,street1 ,w41 ,,and ,,duke ,,street1 ,,stamford ,,street1 ,s4 ,e4