,acid ,rain and ,our ,nation's ,capital ,a ,guide to ,effects on ,buildings and ,monuments by ,elaine ,mc,gee ,for sale by the ,u4,s4 ,government ,printing ,office ,superintendent of ,documents1 ,mail ,stop3 ,,ssop1 ,washington1 ,,dc #bjdjb-icbh ,,isbn #j-af-jdhjfh-,x ,illustration3 ,marble surfaces exposed to rain develop a rough 8sugary0 texture because the calcite grains are loosened as the edges dissolve in the rain water4 ,column capital volute1 ,jefferson ,memorial1 ,washington1 ,d4,c4 ,illustration3 ,a summer rain storm in ,washington1 ,d4 ,c4 7,memorial ,continental ,hall7 ,when polluted air mixes with rain1 snow1 and fog1 acid precipitation forms4 ,this acidity has caused people to worry about the environment2 some reports show that acid rain has affected lakes1 trees1 and fish populations in the ,northeastern ,united ,states and ,canada4 ,another concern is its effect on historic buildings and monuments4 ,the booklet focuses on acid rain and its impact on our ,nation's capital4 ,rain in ,washington1 ,d4 ,c41 has an average acidity of #d4b1 about as acid as a carbonated drink and more than ten times as acid as clean1 unpolluted rain4 ,this booklet will define acid rain1 explain what effects it has on marble and limestone buildings1 and show1 on a walking tour1 some of the places in our ,nation's capital where you can see the impact of acid precipitation4 ,illustration3 ,the p,h scale3 p,h #g is neutral1 neither acid or alkaline2 smaller p,h values are acid1 larger p,h values are alkaline4 ,a liquid with a p,h of #c is ten times as acid as one with a p,h of #d4 #a ,battery ,acid #b4h ,vinegar #d ,adult fish die #e4e ,,acid ,,rain #e4b-f4e ,normal range of precipitation #f-h ,normal range of stream p,h #g ,acid #g ,neutral #g ,alkaline #h4f ,baking soda and sea water #ac ,lye ,what is acid rain8 ,the term 8acid rain0 is commonly used to mean the deposition of acidic components in rain1 snow1 fog1 dew1 or dry particles4 ,the more accurate term is 8acid precipitation40 ,distilled water1 which contains no carbon dioxide1 has a neutral p,h of #g4 ,liquids with a p,h less than #g are acid1 and those with a p,h greater than #g are alkaline 7or basic74 8,clean0 or unpolluted rain has a slightly acidic p,h of #e4f1 because carbon dioxide and water in the air react together to form carbonic acid1 a weak acid4 ,around ,washington1 ,d4,c41 however1 the average rain p,h is between #d4b and #d4d4 ,the extra acidity in rain comes from the reaction of air pollutants1 primarily sulfur oxides and nitrogen oxides1 with water in the air to form strong acids 7like sulfuric and nitric acid74 ,the main sources of these pollutants are vehicles and industrial and power-generating plants4 ,in ,washington1 the main local sources are cars1 trucks1 and buses4 ,acidity in rain is measured by collecting samples of rain and measuring its p,h4 ,to find the distribution of rain acidity1 weather conditions are monitored and rain samples are collected at sites all over the country4 ,the areas of greatest acidity 7lowest p,h values7 are located in the ,northeastern ,united ,states4 ,this pattern of high acidity is caused by the large number of cities1 the dense population1 and the concentration of power and industrial plants in the ,northeast4 ,in addition1 the prevailing wind direction brings storms and pollution to the ,northeast from the ,midwest1 and dust from the soil and rocks in the ,northeastern ,united ,states is less likely to neutralize acidity in the rain4 ,illustration3 ,wet and dry bucket collector1 used to collect samples for measuring rainfall acidity4 ,illustration3 #aiib annual precipitation-weighted mean hydrogen ion concentrations as p,h ,a p,h distribution map shows areas in the continental ,united ,states of greatest acidity in the rain4 ,when you hear or read in the media about the effects of acid rain1 you are usually told about the lakes1 fish1 and trees in ,new ,england and ,canada4 ,however1 we are becoming aware of an additional concern3 many of our historic buildings and monuments are located in the areas of highest acidity4 ,in ,europe1 where buildings are much older and pollution levels have been ten times greater than in the ,united ,states1 there is a growing awareness that pollution and acid rain are accelerating the deterioration of buildings and monuments4 ,stone weathers 7deteriorates7 as part of the normal geologic cycle through natural chemical1 physical1 and biological processes when it is exposed to the environment4 ,this weathering process1 over hundreds of millions of years1 turned the ,appalachian ,mountains from towering peaks as high as the ,rockies to the rounded knobs we see today4 ,our concern is that air pollution1 particularly in urban areas1 may be accelerating the normal1 natural rate of stone deterioration1 so that we may prematurely lose buildings and sculptures of historic or cultural value4 ,what about buildings8 ,many buildings and monuments are made of stone1 and many buildings use stone for decorative trim4 ,granite is now the most widely used stone for buildings1 monuments1 and bridges4 ,limestone is the second most used building stone4 ,it was widely used before ,portland cement became available in the early #aith century because of its uniform color and texture and because it could be easily carved4 ,sandstone from local sources was commonly used in the ,northeastern ,united ,states1 especially before #aijj4 ,nationwide1 marble is used much less often than the other stone types1 but it has been used for many buildings and monuments of historical significance4 ,because of their composition1 some stones are more likely to be damaged by acidic deposition than others4 ,granite is primarily composed of silicate minerals1 like feldspar and quartz1 which are resistant to acid attack4 ,sandstone is also primarily composed of silica and is thus resistant4 ,a few sandstones are less resistant because they contain a carbonate cement that dissolves readily in weak acid4 ,limestone and marble are primarily composed of the mineral calcite 7calcium carbonate71 which dissolves readily in weak acid2 in fact1 this characteristic is often used to identify the mineral calcite4 ,because buildings and monuments made of limestone and marble are more likely to be damaged by acid precipitation1 they are the main focus of this booklet4 ,illustration3 ,memorial ,bridge in ,washington1 ,d4,c41 is made of granite1 the most widely used stone type4 ,illustration3 ,marble used as a trim on the ,first ,bank in ,philadelphia1 ,pennsylvania4 ,how do you recognize limestone and marble8 ,the main difference between limestone and marble is that limestone is a sedimentary rock1 typically composed of calcium carbonate fossils1 and marble is a metamorphic rock4 ,limestone forms when shells1 sand1 and mud are deposited at the bottom of oceans and lakes and over time solidify into rock4 ,marble forms when sedimentary limestone is heated and squeezed by natural rock-forming processes so that the grains recrystallize4 ,if you look closely at a limestone1 you can usually see fossil fragments 7for example1 bits of shell7 held together by a calcite matrix4 ,limestone is more porous than marble1 because there are small openings between the fossil fragments4 ,marble is usually light colored and is composed of crystals of calcite locked together like pieces of a jigsaw puzzle4 ,marble may contain colored streaks that are inclusions of non-calcite minerals4 ,illustration3 ,limestone is made of fossil fragments1 held together with calcite2 the shell near the center is about #a cm across4 ,botanic ,gardens building1 ,washington1 ,d4,c4 ,illustration3 ,marble is made of calcite crystals 7white7 and some colored grains of mica inclusions2 the grains in a marble are locked together like jigsaw puzzle pieces4 ,how does acid precipitation affect marble and limestone buildings8 ,acid precipitation affects stone primarily in two ways3 dissolution and alteration4 ,when sulfurous1 sulfuric1 and nitric acids in polluted air react with the calcite in marble and limestone1 the calcite dissolves4 ,in exposed areas of buildings and statues1 we see roughened surfaces1 removal of material1 and loss of carved details4 ,stone surface material may be lost all over or only in spots that are more reactive4 ,you might expect that sheltered areas of stone buildings and monuments would not be affected by acid precipitation4 ,however1 sheltered areas on limestone and marble buildings and monuments show blackened crusts that have spalled 7peeled7 off in some places1 revealing crumbling stone beneath4 ,this black crust is primarily composed of gypsum1 a mineral that forms from the reaction between calcite1 water1 and sulfuric acid4 ,gypsum is soluble in water2 although it can form anywhere on carbonate stone surfaces that are exposed to sulfur dioxide gas 7,,so71 it is usually washed away4 ,it remains only on protected surfaces that are not directly washed by the rain4 ,gypsum is white1 but the crystals form networks that trap particles of dirt and pollutants1 so the crust looks black4 ,eventually the black crusts blister and spall off1 revealing crumbling stone4 ,illustration3 ,when marble is exposed to acidic rain1 sharp edges and carving details gradually become rounded4 ,antefixes1 roof of the ,philadelphia ,merchants' ,exchange 7built in #ahcb74 ,illustration3 ,blackened crusts on sheltered portions of the limestone ,chicago ,tribune ,building1 ,chicago1 ,illinois4 ,illustration3 ,formed as a result of air pollution1 gypsum alteration crusts have blackened1 blistered1 and spalled from a marble baluster at the ,organization of ,american ,states building1 ,washington1 ,d4,c4 ,illustration3 ,scanning electron microscope photograph of gypsum crystals with dirt and pollution particles trapped by the network of crystals4 ,the scale bar is #aj micrometers long4 ,illustration3 ,a marble column at the ,merchants' ,exchange in ,philadelphia shows loss of material where the stone is exposed to rain and blackening of the stone surface where the stone is sheltered from rain4 ,where can we see the effects of acid precipitation8 ,washington's buildings and monuments use many different stone types4 ,marble and limestone buildings are the most likely to show damage1 because they are more affected by acidic precipitation and urban pollution4 ,as you follow the tour described in this book1 see how granite and sandstone buildings compare with the marble and limestone in the same environment4 ,this guide will help you recognize some geologic features of buildings1 in addition to their historical and architectural aspects1 wherever you travel4 ,however1 remember one important point when examining buildings and monuments for deterioration3 stone deterioration has many causes4 ,although acid precipitation and urban pollution can accelerate stone deterioration1 people1 pigeons1 and other organisms may also harm our stone structures4 ,in addition1 the process of weathering has been going on since the ,earth first had an atmosphere4 ,although we can observe deterioration of the stone1 it is hard to determine how much of the deterioration is from acid precipitation and how much is from other causes4 ,illustration3 ,pigeons sitting on the statue heads have created distinctive deterioration on this building4 ,illustration3 ,flowers and grasses have grown in the cracks between stones on this church4 ,illustration3 ,this limestone column in the ,lincoln ,memorial is darkened and dirty from people's hands touching the stone4 ,illustration3 ,microorganisms have caused this stain to appear on a marble column at the ,jefferson ,memorial4 ,what are we doing about acid rain8 ,scientists from many disciplines are studying acid precipitation and its impact4 ,the ,national ,acid ,precipitation ,assessment ,program 7,,napap71 a ,federal program involving representatives from more than a dozen ,federal agencies1 has sponsored studies on how acid rain forms and how it affects lakes1 crops1 forests1 and materials4 ,because buildings and monuments cannot adapt to changes in the environment1 as plants and animals can1 historic structures may be particularly affected by acid precipitation4 ,scientists are studying effective control technologies to limit the emissions from power plants and automobiles that cause acid rain4 ,the impact and usefulness of regulations that would require limits on air pollution are also being studied4 ,finally1 scientists are examining the processes of deterioration to find effective ways to protect and repair our historic buildings and monuments4 ,agencies like the ,national ,park ,service1 which are charged with protecting and preserving our national heritage1 are particularly concerned not only about the impact of acid rain but also about making the best choices for maintaining and preserving our historic buildings and monuments4 ,illustration3 ,beginning in #aihd1 the ,national ,acid ,precipitation ,assessment ,program sponsored exposure site studies of limestone and marble1 to examine the contribution to stone deterioration that comes from acid precipitation4 ,a field guide to buildings in our ,nation's capital ,washington1 ,d4,c41 has many buildings of historic and cultural significance1 and many of them are made of marble and limestone4 ,this self-guided tour will point out damage to buildings and monuments in our ,nation's capital that may have been caused by acid precipitation4 ,similar effects may be found in other cities as well4 ,places to visit have been divided into several areas1 so the trip can be done either in segments or all in one day4 ,a suggested tour route is described within each area4 ,a car provides the most efficient transport between areas1 but parking may be hard to find4 ,the ,metro subway system can easily be used to visit all areas except the ,jefferson and ,lincoln ,memorials4 ,the closest ,metro stations in each area are shown on the map4 ,you will need comfortable walking shoes1 and you may want to bring along a camera1 a hand lens 7about #aj magnification7 for observing details of minerals and weathering1 and a pair of binoculars for closer examination of inaccessible areas4 ,the area around the ,national ,capitol ,this area includes the ,capitol building1 the ,peace ,monument1 the ,grant ,memorial1 and the ,botanic ,gardens4 ,we begin the tour at the southeast corner of the ,capitol1 and go clockwise around the ,capitol 7along the south1 west1 and then north sides74 ,we then follow a walkway heading west1 from the northeast corner of the ,capitol1 to see the ,peace ,monument at the intersection of ,first ,street and ,pennsylvania ,avenue1 ,,nw4 ,we continue south along ,first ,street to the ,grant ,memorial and then south again to the ,botanic ,gardens4 ,total distance is about one kilometer1 or about three-quarters of a mile4 ,the ,capitol ,building--,site #a ,the ,capitol was built in stages2 the cornerstone of the main building was laid in #agic1 the north wing was completed in #ahjj1 and the south wing was completed in #ahjg4 ,both wings were burned by the ,british in #ahad4 ,the capitol was then rebuilt1 and it has been modified several times throughout the years4 ,a major program of cleaning1 replacement1 and repair was begun in the late #aihj's4 ,the center building of the ,capitol is painted sandstone1 but the north and south wings1 housing the ,senate and the ,house chambers1 are marble4 ,around the ,capitol we will observe various examples of dissolution and blackened alteration1 especially on the marble balustrade that surrounds the south1 west1 and north sides of the building4 ,beginning at the southeast corner of the building1 by using binoculars we can see some areas of blackened alteration in the ,corinthian column capitals4 ,a more accessible example is found under the overhang of the large square ends of the marble balustrade at the southeast corner of the building4 ,the black crust is made of gypsum plus dirt that accumulates in sheltered areas4 ,no black crust is present along the cracks between the stones2 rain water probably flows in these areas1 dissolving the gypsum and preventing accumulation of a crust4 ,not all black areas on this baluster are gypsum2 in some places near the bushes1 you can see greenish-black moss growing on the stone4 ,the top surfaces of the marble balustrade are coarse and rough1 because of dissolution between grains1 compared to areas that are protected from running or washing water where the black alteration crust forms4 ,illustration3 ,the ,united ,states ,capitol building4 ,illustration3 ,blackened alteration has accumulated under the overhanging edge of this marble balustrade corner4 ,southeast corner1 ,u4,s4 ,capitol ,building4 ,illustration3 ,pock marks in marble columns1 south side of ,u4,s4 ,capitol building4 ,silicate mineral inclusions in the marble loosen and fall out when the calcite around them is dissolved by acid rain4 ,another dissolution feature of marble is the pock-mark effect on the square bases of the building columns4 ,silicate mineral inclusions in the marble were loosened by the dissolution of the surrounding calcite1 causing the inclusions to fall out of the stone4 ,a particularly good example of this is found on the fourth column west from the southeast corner of the ,capitol building4 ,the pock-mark dissolution is also found at several other places on the building4 ,illustration3 ,the marble balustrade on the west side of the ,capitol building shows both dissolution and alteration4 ,illustration3 ,a recently replaced marble baluster at the ,capitol has edges that are only beginning to round4 ,illustration3 ,black alteration crusts under the west balustrade of the ,capitol have begun to spall 7peel7 off1 revealing crumbling white marble underneath4 ,we will follow the marble balustrade around the building1 noting differences in deterioration4 ,some parts of the balustrade have obviously been replaced1 thus enabling us to observe various stages in the stone deterioration4 ,the edges of the balusters are sharp when new and become rounded as they age4 ,blackened alteration crusts have accumulated on the sheltered sides of the balusters and under the overhanging top of the balustrade4 ,in some spots under the rail the blackened crust has spalled off1 exposing fresh surfaces and more vulnerable stone4 ,some carvings on the balustrade corners are worn1 whereas others have blackened alteration2 this difference in weathering may be due to local effects of wind and rain4 ,along the steps leading to the terrace on the west side of the ,capitol1 gypsum has accumulated on large areas of the wall4 ,gypsum can accumulate on any surface that is not washed by water4 ,as you walk north along the west side of the ,capitol1 look at the central part of the building4 ,the walls here are painted sandstone4 ,despite recent restoration of the building1 you can see evidence of past stone deterioration1 including the accentuated lines from bedding in the stone and the pock marks where rounded inclusions have disappeared4 ,we will see an example of this same sandstone that is not painted in the buildings near #agth ,street4 ,at the northeast corner of the ,capitol building1 the marble balustrade ends in square blocks like the ones we first examined4 ,here you can see an example of preferential dissolution where the silicate mineral inclusions remain and the calcite around them has been dissolved away4 ,also1 on the north side of this block1 examine the blackened grains on the top surface with a hand lens4 ,not all of the black material you see on stone is gypsum2 some is of biological origin1 probably algae or a fungus4 ,illustration3 ,a marble block that forms the northeast corner of the ,capitol balustrade shows preferential erosion of the calcite around a silicate mineral inclusion4 ,to continue the tour1 follow the pathway that heads west along the north side of the ,capitol1 towards ,first ,street4 ,as you approach ,first ,street you will see a sandstone1 diabase 7a dark igneous rock71 and granite fence with various carvings4 ,because these stone types are resistant to acid attack1 the carvings show little damage4 ,the ,peace ,monument--,site #b ,illustration3 ,the ,peace ,monument1 dedicated in #ahgh1 is made of ,italian marble4 ,this monument1 dedicated in #ahgh1 is made of marble from ,carrara1 ,italy4 ,the statue does not show much damage1 but if you look closely1 you can see alteration crusts 7some are light orange7 in protected places and graininess and roughness in places that are exposed to rain4 ,carved statues present varied surfaces that direct rain washing and runoff4 ,illustration3 ,,map ,,of ,,washington ,sites on the tour3 #a4 ,,the ,,capitol ,,building #b4 ,,the ,,peace ,,monument #c4 ,,the ,,grant ,,memorial #d4 ,,botanic ,,gardens ,,building #e4 ,,jefferson ,,memorial #f4 ,,lincoln ,,memorial #g4 ,,capitol ,,gatehouse #h4 ,,organization ,,of ,,american ,,states ,,building #i4 ,,dar--,,constitution ,,hall #aj4 ,,dar--,,memorial ,,continental ,,hall #aa4 ,,corcoran ,,building #ab4 ,,renwick ,,gallery #ac4 ,,federal ,,triangle ,,buildings #ad4 ,,washington ,,monument ,continue south along ,first ,street to the ,grant ,memorial on your right4 ,the ,grant ,memorial--,site #c ,illustration3 ,the ,grant ,memorial consists of bronze statues on marble bases2 although the statues were cleaned1 the staining on the marble remains4 ,this memorial1 dedicated in #aibb1 consists of a group of bronze sculptures mounted on marble bases4 ,bronze weathers outdoors if it is not cleaned and waxed regularly4 ,like stone1 bronze dissolves where it is exposed to rainfall1 developing a green color and a pitted surface1 and it also alters in sheltered areas1 with accumulation of a blackened layer4 ,the most notable stone deterioration visible here is the green stain on the marble bases1 caused by runoff from the weathered bronze4 ,the green stain does not damage the marble1 but it is unattractive1 and there are no methods currently available to remove the stain without damaging the marble4 ,illustration3 ,the light-green color on the bronze statues at the ,grant ,memorial is typical of the way bronze weathers when it is exposed to acidic rain2 the rain dissolves some of the metal and causes staining of the white marble bases4 ,continue south1 crossing ,maryland ,avenue1 to the ,botanic ,gardens4 ,botanic ,gardens ,building--,site #d ,illustration3 ,the ,botanic ,gardens building is made of limestone4 ,this limestone building was built in #aica4 ,like many of the limestone buildings in ,washington1 this building has been cleaned1 so it does not have an accumulation of surface dirt4 ,however1 the cleaning and regular washing by rainfall have accentuated the fossils in the stone1 which dissolve less readily than the calcite matrix4 ,some of the sculpted heads above the arches of the building show small black crusts4 ,on the east side of the building1 microorganisms naturally present in the stone contribute to the deterioration 7blackening7 of the stone1 where water drips from a joint in the roof4 ,illustration3 ,fossil details stand out on the limestone at the ,botanic ,gardens building2 the fossils are more resistant to dissolution than the calcite matrix that holds the fragments together4 ,the ,botanic ,gardens ,building is the last stop in the ,capitol area of the tour2 you may wish1 however1 to see some bronze alteration on the ,garfield ,memorial 7,first ,st4 and ,maryland ,ave47 and the accentuated fossils with surrounding algae or fungi on the limestone posts near the ,capitol ,reflecting ,pool4 ,the next stop1 the ,jefferson ,memorial1 is about #c4e kilometers 7#b4b miles7 from the ,capitol4 ,jefferson ,memorial--,site #e ,illustration3 ,the ,jefferson ,memorial is made of marble and was dedicated in #aidc4 ,the ,jefferson ,memorial is a marble building1 dedicated in #aidc4 ,one of the most striking deterioration features to observe here is the loss of silicate mineral inclusions in the marble columns because of dissolution of the calcite matrix4 ,close examination of the grooves shows flakes of mica and sometimes grains of pyrite4 ,blackened crusts are visible on the column capitals that are sheltered from rain and from regular washing of the monument4 ,illustration3 ,several of the column shafts at the ,jefferson ,memorial have grooves that follow the inclusion traces in the marble1 where the mineral inclusions have weathered out and been lost4 ,illustration3 ,a close look at some of the weathered grooves in the columns shows that small bits of mica and pyrite remain4 ,the ,national ,park ,service began a survey of the condition of this memorial and the ,lincoln ,memorial in #aiib4 ,the results will be used to help make decisions on treatment1 cleaning1 and preservation4 ,the information gathered from the survey will serve as a known baseline for the condition of the stone1 so that future changes in the condition of the buildings can be assessed4 ,in ,may #aiij1 a part of one of the column capitals 7called a volute7 broke off and fell onto the northwest portico4 ,this failure raised concern about all the volutes at the ,memorial1 so several other cracked volutes were removed1 and studies are being conducted to determine why they cracked4 ,because of where and how the volute broke1 it is unlikely that acid rain or air pollution contributed to the failure4 ,the broken pieces will probably be replaced1 but only when the reason for their failure is understood1 so that an appropriate replacement technique can be chosen4 ,illustration3 ,part of one of the column capitals at the ,jefferson ,memorial broke off and fell onto the portico in #aiij4 ,the next stop is the ,lincoln ,memorial1 #a4h kilometers 7a little more than a mile7 northeast of the ,jefferson ,memorial4 ,lincoln ,memorial--,site #f ,the ,lincoln ,memorial1 dedicated in #aibb1 is made of marble from ,colorado4 ,this building has few alteration crusts1 in part because it receives regular cleaning and in part because of the design of the building4 ,except for the features around the entablature 7the edge of the roof71 there are few sheltered areas where alteration crusts can accumulate4 ,with the aid of binoculars1 you can see some alteration crusts along the underside of the roof overhang2 in these places the marble is very badly crumbled under the alteration crusts4 ,some columns show preferential weathering or loss of inclusions1 but some of this damage might be from graffiti removal4 ,the most visible dissolution feature is sugaring1 where the stone has lost its polish and the surface now feels rough4 ,visitors have affected this popular memorial too2 several of the columns1 especially the limestone columns inside the chamber1 show darkening and rounding of edges where visitors have touched them over the years4 ,one interesting feature at the ,lincoln ,memorial is differences in stone condition that must come from variations in the stone4 ,at several places around the outside of the memorial1 adjacent blocks of marble show very different surface roughness4 ,since the blocks of stone have the same orientation with respect to wind1 rain1 and pollution1 the difference in condition cannot be due to exposure and must be related to basic characteristics in the stone that was used4 ,illustration3 ,the ,lincoln ,memorial is made of marble and was dedicated in #aibb4 ,illustration3 ,under the roof overhang is one of the few places at the ,lincoln ,memorial where alteration crusts have developed on the marble4 ,illustration3 ,some columns at the ,lincoln ,memorial have flattened chalky areas where inclusions have weathered differently from the surrounding calcite4 ,illustration3 ,the marble guttae on the roof overhang are crumbling and falling apart underneath blackened alteration crusts4 ,buildings along #agth ,street1 ,,nw ,some notable examples of stone deterioration are included in this part of our tour4 ,we will begin this segment at the northeast corner of #agth ,street and ,constitution ,avenue1 with the ,capitol ,gatehouse4 ,we will then cross #agth ,street and examine several buildings along #agth ,street as we walk north towards ,pennsylvania ,avenue4 ,the total distance is about three-fourths of a kilometer 7half a mile74 ,capital ,gatehouse--,site #g ,illustration3 ,the ,capitol ,gatehouse1 now located at #agth ,street and ,constitution ,avenue1 is made of the same sandstone used in the ,white ,house and the center part of the ,capitol1 but it was left unpainted4 ,deterioration of this stone is due to the clay it contains1 not to the effects of acid rain4 ,this small sandstone building was built around #ahbh at the west entrance to the ,capitol4 ,in #ahhj it was moved 7along with a twin and four gateposts7 to its present site4 ,this building is made of the same sandstone that was used in the central part of the ,capitol and in the ,white ,house4 ,three types of deterioration are readily visible at the gatehouse3 spalling1 pock marks1 and preferential weathering of clay layers in the stone4 ,this stone may be more degraded than stone in the ,capitol or the ,white ,house1 because of variations in stone quality and maintenance to the buildings and because it has never been painted4 ,illustration3 ,this kind of sandstone was soon found to be a poor building stone because of its tendency to spall4 7detail on ,capitol ,gatehouse7 ,to continue1 we will cross #agth ,street and examine parts of several buildings as we walk north4 ,organization of ,american ,states ,building--,site #h ,illustration3 ,the ,organization of ,american ,states ,building is made of marble and was dedicated in #aiaj4 ,this marble building was dedicated in #aiaj4 ,two sculptures in the front of the building show some alteration crusts in sheltered areas and dissolution in exposed areas4 ,in back of the building the marble balusters on the patio are covered with blackened crusts1 especially on the sides facing the garden4 ,in many places the crusts have blistered or spalled off1 exposing new surfaces to alteration4 ,in general1 the patio sides of the balusters are in much better condition than the sides that face the garden1 perhaps because washing of the patio has washed off the gypsum crusts on that side of the balusters4 ,illustration3 ,blackened gypsum crusts may blister and spall off1 exposing a crumbling stone surface to further pollution4 ,continue north through the garden and parking lot and cross ,c ,street to the ,daughters of the ,american ,revolution 7,,dar7 ,buildings4 ,,dar--,constitution ,hall--,site #i ,illustration3 ,,dar--,constitution ,hall is made of limestone and was built in the #aicj's4 ,the main damage on this limestone building1 built in the #aicj's1 is the blackening of the side balustrade from algae or fungi4 ,the stone is porous and therefore retains moisture1 thus encouraging growth of organisms4 ,the limestone in this building is quite uniform and shows little preferential dissolution1 except in a few places4 ,on the top of the balustrade along ,c ,street1 for example1 some of the calcite matrix has dissolved from around the fossil fragments1 and some holes are filled with calcite crystals4 ,illustration3 ,some of the blackening on limestone surfaces may be from algae or fungi that readily grow in the rough surface in ,washington's warm1 humid climate4 ,continue east along ,c ,street to ,memorial ,continental ,hall4 ,,dar--,memorial ,continental ,hall--,site #aj ,illustration3 ,memorial ,continental ,hall1 built in #aiji1 is part of the ,daughters of the ,american ,revolution building complex4 ,illustration3 ,carvings at the base of the columns on the south side of ,memorial ,continental ,hall show that carved details and sharp edges remain on sheltered areas4 ,the porch area on the south side of this marble building built in #aiji is a good place to look at some contrasts in marble deterioration4 ,parts of the balustrade have been replaced1 as shown by differences in color and surface roughness of the stone4 ,the exposed stone surface along the top of the balustrade is rougher than the surfaces in more sheltered areas4 ,the columns on this porch are carved around the base1 so you can examine the effects of exposure to rain on the carving details4 ,the more exposed carvings have lost their sharp edges and definition compared to the sheltered carvings4 ,the bases of the columns contain small amounts of pyrite1 which is more resistant to weathering than is the calcite in the marble surrounding the pyrite4 ,the sheltered part of the window-sill support on the west side of the porch shows an alteration crust1 a dull gray accumulation on the stone surface4 ,illustration3 ,on an exposed portion of the carving on the columns at ,memorial ,continental ,hall1 the edges of the marble have rounded and the surface has roughened4 ,illustration3 ,pyrite grains stand in relief where calcite and micas have weathered out of the marble at ,memorial ,continental ,hall4 ,illustration3 ,a dull gray surface on the marble on the window-sill support shows where an alteration crust is just beginning to develop4 ,at the corner of #agth and ,c ,streets1 turn left and walk north along #agth ,street4 ,on our way to the ,corcoran ,gallery1 we will pass the ,red ,cross building 7marble1 #aiag74 ,some of the same types of marble deterioration observed at other locations are also present here4 ,corcoran ,gallery--,site #aa ,illustration3 ,the ,corcoran ,gallery is built mostly of marble4 ,the ,corcoran ,gallery is marble with a granite base4 ,it was built in #ahgi and enlarged in #aibg4 ,ornate carvings around the roof1 doors1 and windows have blackened crusts of gypsum1 as do parts of the marble pedestals supporting the bronze lions at the front door4 ,the marble bases also have inclusions that stand out above the surrounding calcite1 which has been dissolved away4 ,illustration3 ,marble bases for bronze lions outside the entrance to the ,corcoran ,gallery have feldspar inclusions that stand in relief compared to the roughened surrounding calcite4 ,continuing north along #agth ,street towards ,pennsylvania ,avenue1 you will see several modern granite office buildings and the ,executive ,office building 7formerly the ,state-,war and ,navy building71 which was built from granite and completed in #ahhh4 ,these granite buildings show little deterioration4 ,turn right onto ,pennsylvania ,avenue and proceed to the ,renwick ,galley on the northeast corner of the intersection of #agth ,streets and ,pennsylvania ,avenue4 ,renwick ,gallery--,site #ab ,illustration3 ,the ,renwick ,gallery1 made of brick and sandstone1 was completed in #ahei4 ,this building of brick and sandstone1 completed in #ahei1 is interesting from a stone preservation point of view4 ,the decorative sandstone panels were badly deteriorated1 so in #aifh the panels were saturated with epoxy to strengthen them4 ,this treatment actually accelerated the deterioration because when water penetrated behind the epoxy-filled area1 large portions of the treated panels spalled off4 ,a second renovation attempt was therefore necessary two years after the first1 and the present panels are cast sandstone4 ,a post of the original sandstone stands at the southeast corner of the building4 ,illustration3 ,casts of ground sandstone and epoxy replaced the original carved sandstone decorative trim at the ,renwick ,gallery when a first attempt to preserve the carved stone failed4 ,the next part of the tour begins at #aeth ,street and ,pennsylvania ,avenue ,s4 ,to get there1 walk east along ,pennsylvania ,avenue1 past ,blair ,house and between ,lafayette ,park and the ,white ,house4 ,lafayette ,park has a number of bronze statues that have been cleaned fairly recently4 ,the ,white ,house is built of sandstone that was painted white2 the paint was used in part to improve the durability of the stone4 ,after you pass the ,white ,house1 you will come to the ,treasury ,building4 ,turn right onto #aeth ,street and walk south1 towards the ,washington ,monument and the ,mall4 ,the total distance from the ,renwick to the corner of #aeth and ,pennsylvania is about three-fourths of a kilometer 7half a mile74 ,federal ,triangle ,buildings--,site #ac ,on the east side of #aeth ,street1 beginning at ,e ,street1 is the ,commerce ,department building1 which was constructed of limestone in the #aicj's4 ,this building is part of the ,federal ,triangle1 a cluster of ,federal office buildings in the area bounded by ,pennsylvania ,avenue1 ,constitution ,avenue1 and #aeth ,street1 built primarily during the ,new ,deal administration of ,president ,franklin ,d4 ,roosevelt4 ,some sculptures on the buildings were done by participants in the ,,wpa program4 ,these buildings were cleaned in the #aifj's1 probably by sandblasting4 ,look for fossils in relief and alteration crusts in some sheltered places on the carved work4 ,some of the blackening on this building is from dirt and organic material trapped or growing in the rough surface of the stone4 ,illustration3 ,all of the ,federal buildings that form the ,federal ,triangle 7between ,pennsylvania ,avenue1 ,constitution ,avenue1 and #aeth ,street7 are made of limestone4 ,continue south on #aeth ,street to ,constitution ,avenue4 ,from the corner of #aeth ,street and ,constitution1 follow some of the foot paths half a kilometer 7three tenths of a mile7 to the ,washington ,monument4 ,washington ,monument--,site #ad ,this monument was begun in #ahdh1 but it was not finished until #ahhe2 the change in color about #aej feet up marks a change in the type of marble used to face the monument4 ,although it is made of marble1 its smooth1 straight shape and the massive blocks used in this monument have minimized the effect of acid precipitation4 ,dissolution does occur in a few areas1 but the amount of stone material lost from dissolution is insignificant compared to the mass of the stone4 ,illustration3 ,the straight shape and massive stones in the ,washington ,monument minimize the impact of acid precipitation to this important landmark4 ,our tour ends here1 but there are many more stone buildings and monuments in ,washington and in other cities that may also show the effects of urban pollution and acid precipitation4 ,however1 as seen on this tour1 not all of the deterioration of stone buildings is caused by acid rain4 ,to protect our historic stone buildings and monuments1 we need to limit air pollution that contributes to acid rain deterioration1 and we need to develop effective maintenance and preservation procedures that will not further harm the stone4 ,glossary of ,geologic and ,architectural ,terms ,antefix--an ornament along the edge of a roof1 often shaped like a shell or shield ,baluster--a post or support for a handrail ,balustrade--a rail and row of supporting posts1 especially along a stair or porch ,bronze--a metal alloy of copper and tin2 although brown when fresh1 it weathers to a more commonly seen green color ,calcite--a mineral composed of calcium carbonate3 ,ca,c,o ,column ,capital--,the top portion of a column4 ,there are three main types2 from least ornate to most ornate1 they are ,doric1 ,ionic1 and ,corinthian ,diabase--a dark-gray to black1 fine-textured igneous rock1 composed of the minerals feldspar and pyroxene ,feldspar--a common mineral composed of silica 7,si71 aluminum 7,al71 and calcium 7,ca71 potassium 7,k71 or sodium 7,na73 ,ca,al,si,o1 ,k,al,si,o1 ,na,al,si,o ,fossil--remains or trace of a plant or animal preserved in a rock from some past1 prehistoric time ,granite--a light or speckled1 coarse-grained igneous rock composed of quartz1 feldspar1 and mica ,guttae--small1 drop-like rounded ornaments under a roof overhang ,gypsum--a mineral composed of hydrated calcium sulfate3 ,ca,s,o#b;,h,o ,igneous--formed from melted or partially molten rock ,inclusion--a mineral phase that is distinct 7in composition or appearance7 from the main mineral components of a rock ,limestone--a sedimentary rock1 chiefly composed of calcium carbonate2 formed from the shells of marine animals ,marble--a metamorphic rock1 chiefly composed of calcium carbonate ,metamorphic--changed2 usually by heat or pressure to a different form but the same composition ,mica--a silicate mineral that forms sheets or layers and contains aluminum1 hydroxyl1 and alkali ions3 ,k,al,si,al,o7,,oh1,f71 ,k7,mg1,fe7,si,al,o7,,oh1,f7 ,mineral--a naturally occurring inorganic substance with an ordered structure2 rocks are made of one or more minerals ,portico--a porch1 with a roof supported by columns ,pyrite--a mineral 78fool's gold07 composed of iron sulfide3 ,fe,s ,pyroxene--a silicate mineral containing two metal oxides3 ,ca,mg,si,o1 ,ca,fe,si,o1 7,mg1,fe7,si,o ,quartz--a mineral composed of silicon dioxide1 or silica3 ,si,o ,sandstone--a sedimentary rock composed chiefly of quartz grains ,sedimentary--formed from particles that were transported by water or wind and deposited in layers ,volute--a scroll-like ornament on an ,ionic column capital ,further ,reading ,acid rain3 ,the facts1 #aihh3 available from ,inquiry ,centre1 ,environment ,canada1 ,ottawa1 ,ontario1 ,canada ,k#a;,a #j;,h#c4 ,amoroso1 ,g4,g41 and ,fassina1 ,v41 #aihc1 ,stone decay and conservation3 ,new ,york1 ,elsevier1 #dec p4 ,hannibal1 ,j4,t41 and ,park1 ,l4,e41 #aiib1 ,a guide to selected sources of information on stone used for buildings1 monuments1 and works of art3 ,journal of ,geological ,education1 v4 #dj1 p4 #ab-bd4 ,pickering1 ,r4,j41 #aihg1 ,acid rain3 ,u4,s4 ,geological ,survey ,open-,file ,report #hg-cii4 ,u4,s4 ,geological ,survey1 ,building stones of our ,nation's ,capital3 ,reston1 ,va41 ,u4,s4 ,geological ,survey general-interest publication4 ,winkler1 ,e4,m41 #aigc1 ,stone3 ,properties1 durability in man's environment3 ,new ,york1 ,springer-,verlag1 #bcj p4 ,illustration3 ,limestone ,illustration3 ,marble ,illustration3 ,sandstone ,illustration3 ,granite ,photographs by the author ,edited by ,kathleen ,gohn ,publication design by ,elizabeth ,junek ,u4,s4 ,government ,printing ,office3 #aiie-cid-ijd ,what ,type of ,rock is ,it8 ,look at the overall appearance of the stone in the building4 ,observe the color1 texture1 and structure of the stone4 ,does the stone look evenly colored1 with an even texture8 ,,yes ,look at the grains up close4 ,do you see fossil fragments 7bits of shells or skeletons78 ,,yes ,,limestone ,,no ,are the grains rounded1 like sand on the beach8 ,,yes ,,sandstone ,,no same as next line ,,no ,do you see streaks or clouds of color in a mostly white stone8 ,,yes ,,marble ,,no ,look at the grains up close4 ,do you see a mixture of colors 7black1 white1 gray1 maybe pink or red78 ,,yes ,,granite ,,no ,,marble ,some of these stones may have layers that were the original beds that formed the stones4 ,illustration3 ,,limestone ,illustration3 ,,sandstone ,the grains in these rocks may look like crystals that fit together like jigsaw puzzle pieces4 ,illustration3 ,,marble ,illustration3 ,,granite ,illustration3 ,department of the ,interior ,march #c1 #ahdi ,as the ,nation's principal conservation agency1 the ,department of the ,interior has responsibility for most of our nationally owned public lands and natural and cultural resources4 ,this includes fostering sound use of our land and water resources2 protecting our fish1 wildlife1 and biological diversity2 preserving the environmental and cultural values of our national parks and historical places2 and providing for the enjoyment of life through outdoor recreation4 ,the ,department assesses our energy and mineral resources and works to ensure that their development is in the best interests of all our people by encouraging stewardship and citizen participation in their care4 ,the ,department also has a major responsibility for ,american ,indian reservation communities and for people who live in island territories under ,u4,s4 administration4 ,this publication is one of a series of general interest publications prepared by the ,u4,s4 ,geological ,survey to provide information about the earth sciences1 natural resources1 and the environment4 ,to obtain a catalog of additional titles in the series 8,general ,interest ,publications of the ,u4,s4 ,geological ,survey10 write3 ,u4,s4 ,geological ,survey ,information ,services ,p4,o4 ,box #bebhf ,denver1 ,,co #hjbbe ,transcriber's ,notes --,retained publication information from the printed edition3 this e,book is public-domain in the country of publication4 --,in the text versions only1 text in italics is delimited by underscores4