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Lesson1WhatIsAMineral
BecausetheMajorityofgemstonesaretraditionallyminerals,theirhistoryis
intimatelyandinextricablyassociatedwiththehistoryofminerals.Earlyman
undoubtedlydiscoveredbyaccidentthatquartzandflintcouldbebrokentoproduce
sharpcuttingedgesthatcouldbeusedastoolsorweapons.Itwasthroughtheuseof
mineralsthatbebeganhislongjourneytocivilization.
Sincemostgemmaterialsareminerals,itisimportantatthebeginningofastudy
ofgemologytounderstandthetermmineral.Itisimpossibletogiveabriefdefinition
thatisacceptabletoallmineralogists.Yetwithminorqualificationsmostofthem
agreewiththefollowing:
Amineralisanaturallyoccurring,crystallizedchemicalelementorcompound
havingeitheradefinitechemicalcompositionorrangeincompositionandusually
formedasaproductofinorganicprocesses.
Letusconsidereachofthepartsofthisdefinitionandpointouttheexceptionsor
qualifications.
Naturallyoccurringimpliesthatmineralsareproductsofnature.However,many
compoundsthatarefoundasmineralshavebeenpurposelysynthesizedbymanand
haveessentiallyidenticalproperties.Strictlythesearenotmineralsbutmaybe
consideredsyntheticmineralstodistinguishthemfromnaturalproducts.
Acrystallizedchemicalelementorcompoundimpliesthatmineralsaresolids
composedofatomsorionsarrangedinaregularthree-dimensionalpattern.Such
solidshavecompositionsexpressiblebychemicalformulas.Somemineralshave
definitecompositions;forexample,quartz(rockcrystal,citrine,andamethyst)is
silicondioxide,SiC)2,andcorundum(rubyandsapphire)isaluminumoxide,AI2O3.
Othershavearangeincompositioninwhichatomsofoneelementsubstitutefor
atomsofanotherelementinthecrystalstructure.Forexample,themineralgroup
olivinehasasone-memberpuremagnesiumsilicate,MgzSQ;butironusually
substitutesforsomemagnesiumasinthegemvarietyperidot,andtheformulais
written(Mg,Fe)2SiC)4.
Therestrictionthatmineralsbecrystallineexcludesliquidsandnoncrystalline
solids,althoughtheyarelikemineralsinchemistryandoccurrence.Inarigorous
classificationsuchsubstancesarecalledmineraloids.Althoughopalisessentially
noncrystallineandthusfallsinthisgroup,itistreatedinthetextasamineral.
Thereareafewnaturalnoncrystallinesolidscalledmetamictmineralsthatare
classedasmineraloids.Whenoriginallyformed,thesewerecrystalline,butthecrystal
structurehasbeendestroyedbyradiationfromradioactiveelements.Theonly
importantmetamictmineralusedasagemisonetypeofzircon.
Usuallyformedasaproductofinorganicprocessesimpliesthatsubstances
formedunderbiogenicprocessesarenormallyexcluded.Afewnaturalsubstancescan
originatethroughbothorganicandinorganicagencieswiththetwotypeshaving
identicalproperties.Suchorganicallyproducedmaterialsarehereconsideredminerals.
Thetwomostimportantgemmaterialscontainingamineralhavingthisdualorigin
arepearlandmother-of-pearl.
Vocabulary
mineral矿物crystallize结晶
majority大多数,大半composition成分
gemstone宝石inorganic无机的
traditionally传统地imply含有…的意思;暗示
intimately密切地synthesize合成
inextricably分不开地atom原子
byaccident偶然ion离子
quartz石英three-dimensionalpattern三度(维)模型
flint燧石rockcrystal水晶
gemology石英钟citrine黄晶
mineralogist矿物学家amethyst紫晶
qualification保留;资格silicon(Si)硅
2
dioxide二氧化物crystalline晶质(体)
corundum冈lj玉rigorous严格的,严密的
ruby红宝石classification分类
sapphire蓝宝石mineraloid似矿物
aluminum(Al)铝metamict蜕晶质
oxide氧化物noncrystalline非晶质
crystalstructure晶体结构radiation辐射
olivine橄榄石radioactiveelement放射性元素
magnesium(Mg)镁zircon错石
silicate硅酸盐biogenic生物的
variety品种;异种;亚种organic有机的
peridot橄榄石agency作用力,营力
restriction限制,限定dual双重的
exclude排除pearl珍珠
ReadingMaterial1GemMinerals
Becauseamineralmusthavecertainqualificationstobeplacedinthespecial
categoryofgemminerals,thenumberislimited.Ofmorethan3000knownmineral
species,approximately70meettherequirementsandoftheseabout15canbe
consideredasimportantgemminerals.
Intheabovelist(seeTable1-1)thesemineralsarearrangedbychemicalgroups,
theorderinwhichtheyaredescribedonmineralogy,withthenameofthemore
importantgemmineralsinboldfacetype.However,itshouldbepointedout,thatthe
listisnotall-inclusiveandthatotherrarermineralsoccasionallyappearasgemstones.
Thegemologistisfrequentlycalledupontoidentifythemineralsfromwhich
ornamentalobjectshavebeencarved.Therefore,includedinTable1-1(GemMinerals)
aresomemorecommonlyusedforcarvingsthanforcutstones.
3
Table1-1GemMinerals
Nativeelements1Diamond
Sulfides2Sphalerite,Pyrite
Corundum,Hematite,Rutile,Quartz,Anatase,Cassiterite,Spinel,
Oxides9
Chrysoberyl,Opal
Halides1Fluorite
Carbonates6Calcite,Rhodochrosite,Smithsonite,Aragonite,Malachite,Azurite
Sulfates1Gypsum
Tungstates1Scheelite
Beryllonite,Apatite,Amblygonite,Brazilianite,Turquoise,
Phosphates6
Variscite
Phenacite,Willemite,Olivine,Garnet,Zircon,EuclaseAndalusite,
Sillimanite,Kyanite,Topaz,Staurolite,Dalolite,Titanite,Benitoite,
Zoisite,Epidote,Vesuvianite,Axinite,Beryl,Cordierite,
Silicates39Tourmaline,Diopside,Enstatite-hypersthene,Jadeite(jade),
Spodumene,Rhodonite,Tremolite-aclinolite(nephrite-jade),
Serpentine,Talc,Prehnite,Chrysocolla,Dioptase,Feldspar,
Danburite,Sodalite,Lazurite,Petalite,Scapolite,Thomsonite
Total66
Vocabulary
category种类sphalerite闪锌矿
species种,物种pyrite黄铁矿
approximately大约,大致hematite赤铁矿
boldfacetype粗体字,黑体字rutile金红石
gemologist宝石学家anatase锐钛矿
ornamental装饰的cassiterite锡石
carve雕刻,切割spinel尖晶石
carving雕刻品chrysoberyl金绿宝石
4
opal欧泊,蛋白石zoisite黝帘石
fluorite萤石epidote绿帘石
calcite方解石vesuvianite符山石
rhodochrosite菱镁矿azinite斧石
smithsonite菱锌矿beryl绿柱石
aragonite文石(霰石)cordierite堇青石
malachite孔雀石tourmaline电气石,碧玺
azurite蓝铜矿enstatite-hypersthene顽火辉石一紫苏辉石
gypsum石膏diopside透辉石
scheelite白鸽矿jadeite硬玉,翡翠
beryllonite磷钠被石jade玉
apatite磷灰石spodumene锂辉石
amblygonite磷铝锂石rhodonite蔷薇辉石
brazillianite磷铝钠石tremolite透闪石
turquoise绿松石actinolite阳起石
variscite磷铝石nephrite软玉
phenacite硅被石serpentine蛇纹石
willemite硅锌矿talc滑石
garnet石榴石,紫牙乌prehnite葡萄石
euclase蓝柱石chrysocolla硅孔雀石
andalusite红柱石dioptase透视石
silimanite矽线石feldspar长石
kyanite蓝晶石danburite赛黄晶
topaz黄玉,托帕石sodalite方钠石
staurolite十字石lazurite青金石
datolite硅硼钙石petalite透锂长石
titanite楣石scapolite方柱石
benitoite蓝锥矿thomsonite杆沸石
5
Lesson2GemQualifications
Thetermgem(orgemstone)isappliedtothesematerials,usuallyaftertheyare
cutandpolished,thataresufficientlyattractiveanddurabletobeusedforpersonal
adornment.
Oftheseveralattributesofgemstones,beautyisthemostimportant.Thatbeauty
isintheeyeofthebeholderisastruewithgemsaswithmanyotherthings.Toone,
beautymaybeinthecolor;toothers,itmaybeintheluster,transparency,or
brilliancyandthefireresultingfromskillfulcuttingbythelapidary.Thebeautyof
mostgemsresultsfromacombinationoftwoormoreoftheseproperties,butinsome
nontransparentstones,suchasturquoiseandmalachite,itliesincoloralone.Allthe
factorscontributingtobeautyarefoundinafewgemstonessuchasfancycolored
diamondsanddemantoidgarnet.Opal,oneofthemostbeautifulgems,owesits
attractivenesstoflashesofspectralcolorsdiffractedfromthestone'sinterior,a
phenomenonknownasplayofcolor.
Becausemostgemstonesareusedforpersonaladornment,theyshouldbeableto
resistscratchingandabrasionwhichwoulddulltheirlusterandmartheirbeauty.Thus
durability,whichdependsonhardness,toughnessandstability,isthesecondrequisite
ofagemmineral.Itisgenerallyconsideredthatagemstonehardenoughtoresist
abrasionshouldhaveaminimumhardnessof7,thatofquartz.Only10or12gems
satisfythisrequirement,butothersfashionedfromsoftermineralswillretaintheir
lusterformanyyearsifwornwithcare.Thehighhardnessofdiamond,ruby,sapphire
andemeraldisamajorfactorinplacingthemamongthemostprizedofgems.
However,somehardmineralsarebrittleandcanbechippedorfracturedifstrucka
sharpblow,whereasothermineralsoflesshardnessmaybethoughandresist
fracturing.Thelattercaseisparticularlytrueofnephritejade,whichiscomposedofa
feltedaggregateoffibrouscrystals.Theblowthatwouldshatteradiamondwould
havelittleeffectonthefarsofternephritejade.
Stabilityisagemstonesabilitytoresistlossofcolorduetoheat,light,or
chemicalattack.Whileitisafactortoconsider,italonerarelypreventsamineral
6
frombeingusedasagemstone.
Beautyanddurabilityarethetwoinherentpropertiesofamineralonwhichits
useasagemdepends.Comparedtotheseproperties,otherqualificationsarerelatively
superficialanddependmostlyonthewhimsofman.Sinceitishumannaturetodesire
somethingrare,rarityisanothercriterionofagemsvalue.Ifthereisonlyalimited
quantityofagemmineralreachingthemarket,thepriceishigh,andbecauseofthis,
thegemisconsidereddesirablebythefewwhocanaffordit.Withthediscoveryof
newsources,resultinginagreatincreaseinsupply,thepricefalls.Itlosesitsappeal
tothefewwhoformerlycouldaffordit.
Thedesirabilityofgemsisalsosubjecttothevagariesoffashion.Forexample,a
darkredvarietyofgarnet-pyropewasextremelypopularduringthenineteenth
centuryandisseeninmanypiecesofjewelrydatingfromthattime,butisinlittle
demandtoday.
Afinalfactorthatcanbeaddedtothedesirablepropertiesofgemsisportability.
Thisisparticularlyappealingforpeoplelivinginpoliticallyunstablecountriesfrom
whichtheymaybeforcedtofleeonshortnotice.Gemstonesareuniqueincombining
highvaluewithsmallvolumeandweightandcanbetransportedeasilyfromone
countrytoanotherduringperiodsofpoliticalunrestandeconomicinstability.Itis
interestingtonoteinthisregardthatevenmanyoftheleastexpensivegemmaterials
are,byweight,morecostlythangold.
Althoughquiteunrelatedtotheintrinsicpropertiesofagem,rarity,fashion,and
portabilityplayalargepartindeterminingitsvalue.
Vocabulary
sufficiently足够地beholder观看者
attractive有吸引力的luster光泽
durable耐久的transparency透明度
adornment装饰brilliancy光亮,光彩
attribute特质,属性skillful巧妙的,精巧的
7
cutting琢磨lapidary宝石工,玉工
lie在于aggregate集合体
demantoid翠榴石shatter打碎
attractiveness有吸引力inherent固有的,本来的
flash闪光superficial浅薄的
interior内部whim好奇
spectralcolors光谱色彩rarity稀罕,珍奇
diffract分解afford能买得起
phenomenon现象appeal引起…共鸣,投合…心意
playofcolor变彩desirability合意性
scratching刻划vagary变幻,幻想
abrasion擦磨,刮削fashion潮流,风气
durability耐久性pryope镁铝榴石
hardness硬度jewelry珠宝饰物,首饰
toughness韧性portability轻便
stability稳定性flee消失,消散
requisite要素,必需品unique唯一的
fashioned制作unrest不安定
emerald祖母绿instability不稳定
brittle脆的intrinsic(al)内在的,本质的
chip破碎determine确定,鉴定
blow打击
8
ReadingMaterial2ClassificationofGems
Thesystemusedbygemologiststoclassifygemstonesisbasedonafewgeneral
categories.Anunderstandingofthesecangoalongway,therefore,tounderstanding
thedescriptivenamesusedforgems,whethertheyarenaturalorman-made,organic
orinorganic.
Thebasiccategoryisthegemspecies.Themajorityofgemspeciesareminerals,
thatisdefinedbyadefinitechemicalcompositionandusuallyacharacteristiccrystal
structure.Corundumandberylaretwosuchmineralspeciesthatarealsogemspecies.
Inaddition,thereareanumberoforganicgemmaterialsthatarealsoconsideredgem
speciesalthoughtheywouldnotbeincludedassuchinastrictmineralogical
classification.Amongtheseorganicgemspeciesarepearl,coral,shell,amber,jet,and
ivory.
Gemologicalspeciesarebrokendownintovarieties.Thesearesubdivisionsof
speciesbasedincolor,colordistribution,transparency,andopticalphenomena.The
followingexamplesmayhelptoclarifythisconcept:Corundumisagemspecies,the
gemmineralcomposedofaluminumoxidecrystallizinginthetrigonalsystem.The
mediumtodarkorangeredtopurplishredvarietyiscalledruby,thebluevarietyis
calledsapphire,andallothercolorsaretermedfancysapphiresanddesignatedby
theircolor,forexample,pinksapphireandgreensapphire.Inberyl,anothergem(also
mineral)species,thesaturatedmediumtodarkgreenvarietyiscalledemerald,lightto
mediumblueisaquamarine,pinkismorganite,andyellowisgoldenberyl.With
respecttocolordistribution,chalcedony(afine-grainedvarietyofquartz)with
straightblackandwhitebandingiscalledonyx,whereasitiscalledagateifthe
bandingiscurvedorangular.Asfortransparency,atranslucentreddishchalcedonyis
calledcarnelian;anotherfine-grainedvarietyofquartzthatisredandnearlyopaqueis
calledjasper.Finally,somegemmaterialsexhibitunusualopticaleffectscalled
phenomena.Onesuchphenomenonisthestar-effect,orasterism.Starstonesexhibit
interestingbandsoflightintheircurvedsurfaces.Ifasapphireexhibitsthiseffect,it
9
isthestarsapphirevariety;ifarubyexhibitsthiseffect,thenitiscalledstarruby.The
othergems,suchasrosequartz,almandinegarnet,anddiopside(anearlyblack
variety),frequentlyalsoshowstareffect(asterism),andoccasionallyberylandspinel
exhibitasterism.
Agemologicalgroupisdefinedastwoormorechemicallyrelatedgemmineral
speciesthataresimilarinstructureandproperties.Thegarnetsandfeldsparsaretwo
importantgemgroups.Thegarnetgroupincludesthatthegemmineralspeciesand
varietyarepyrope,almandine,grossularite(hessoniteoressonite),tsavolite,andradite,
demantoid,spessartine,uvarovite,etc.Thefeldspargroupincludesthatthegem
mineralspeciesandvarietyarealbite,labradorite,moonstone,sunstone,amazonite,
oligoclase,orthoclase,etc.
Vocabulary
trigonalsystem三方晶系spessartine铺铝榴石
tsavolite铭锐钙铝榴石almandine铁铝榴石
oligoclase奥长石uvarovite钙铭榴石
morganite钠绿柱石grossularite钙铝榴石(绿榴石)
andradite钙铁榴石albite钠长石
orthoclase正长石hessonite钙铝榴石(黄榴石)
diopside透辉石labradorite拉长石
demantoid翠榴石essonite钙铝榴石(黄榴石)
pyrope镁铝榴石amazonite天河石
10
Lesson3GemologyandMineralogy
Gemologyisarelativelynewsciencethatissodeeplyrootedinmineralogyitis
impossibletodrawalinebetweenthem.Thegemologistcanbeconsideredinsome
respectsamineralogistspecializingingemminerals.Inthebroadsensetheseinclude
thenaturalornamentalmaterialsusedforcarvingsanddecorativepurposes.In
addition,today'sgemologistmustdealwithanumberofareasbeyondtheconcernof
themineralogist,includingthegradingandevaluationofgemsandeventheir
marketingandsale.
Mineralogyisnotafundamentalsciencebutasynthesisofchemistry,physics,
andgeology.Asaspecializedmineralogist,thegemologistmustdrawonthese
sciencesforacompleteunderstandingofthesubject.Thephysicsandchemistryof
mineralsareintimatelyrelated,forthecomplexphysicalandchemicalpropertiesthat
characterizeamineraldependonthechemicalcompositionandthearrangementof
theatomsinthecrystalstructure.Fromgeologycomesanunderstandingofthe
physicochemicalconditionsunderwhichmineralsform.Furthennore,onlywiththe
knowledgeofgeologycantherebeanintelligentapproachtoprospectingforgemsor
anappreciationoftheproblemsofextractingthemfromtheenclosingrock.
Althoughsimilarequipmentandsimilarmethodsofstudyareusedbyboth
mineralogistandgemologist,thereisafundamentaldifferenceinapproach.The
mineralogistcanscratch,powder,ordissolveinacidtheobjectsofstudywith
impunity.Thegemologistpresentedwithavaluablefacetedstoneisrestrictedto
nondestructivetestsandmeasurements.Togathersufficientdatatoidentifysucha
gemstone,thegemologisthasdevelopedspecialinstrumentsandtechniques.Inthe
textthesedevicesandmethodsareemphasized.
Vocabulary
mineralogy矿物学grading分等级
specialize专门研究evaluation估价,评价
decorative装饰的marketing营销,市场营销
ii
sale销售equipment设备
fundamental基础的,根本的scratch刻,划
synthesis合成powder磨碎
geology地质学impunity无虑,无患
characterize特征restrict限制,禁止
physicochemical物理化学的nondestructive无损害的
intelligent有理解力的measurement测定,测量
approach门道,手段gather搜集
prospecting寻找,探查sufficient充分的,充足的
appreciation评价,判断device手段
extracting提取,选出emphasize强调
ReadingMaterial3OriginandOccurrenceofGemstones
Althoughgemologyisarelativelynewscience,gemshavebeenknownforalong
time.Eversincethefirstchancediscoveriesbyearlyman,gemshavebeeneagerly
soughtandhighlyvalued.Gemstonesaretraditionallyminerals,thatistheyare
elementsorinorganiccompoundsformedasproductsofnature.Withadvancing
technologyandabetterunderstandingofnature'sgem-formingprocesses,manhas
beenabletomanufacturesubstancesthatareusedasgems,someidentical,ornearly
identical,tomineralsandothershavenonaturalcounteiparts.Therefore,acomplete
discussionoftheoriginofgemmaterialsmustincludethemethodsusedbymanas
wellastheearthprocessesthathavebeenworkingthroughoutgeologictime.This
lessongivesabriefaccountoftheoriginandoccurrenceofgemstonesinnature.
Todiscusstheoriginofgemstonesistodiscusstheoriginofminerals.Many
mineralsoriginateinavarietyofways,anditistheexceptionalmineralforwhicha
singleexplanationcanaccountforalloccurrences.Soitiswithgems.Butinthe
limitedspaceavailable,onlytheprincipalprocessesresponsibleforgemformation
areconsidered.
Onlysixoftheapproximately3000mineralsareuniversallyabundant.These
12
majorrock-formingmineralsormineralgroupsthatmakeup95%oftheearth'scrust
arelistedinTable1.Withtheexceptionofquartz,thenamesinthetableareof
mineralgroups,eachofwhichhasseveralmembersthatdifferchemicallyfromeach
other.Butallthesecommonandabundantminerals,andquartzaswell,havevarieties
that,becauseofunusualconditionsofformation,occuringem-qualitymaterial.Even
thesoft,platymineralstalcandmica,whenfinegrainedandcompact,aresometimes
fashionedintoornamentalobjects.
Table1MajorRock-formingMinerals
MineralPercentageofEarth'sCrustPrincipalElements
Feldspar60Na,K,Ca,Al,Si,0
Quartz13Si,0
Pyroxene12Mg,Fe,Ca,Na,Al
Amphibole5Ti,Mn,Si,0
Mica4K,Mg,Fe,Al,Si,0
Olivine1Mg,Fe,Si,0
Thematerialsavailableformineralformationarethe92elementsfoundonearth
ofwhichonly8makeupnearly99%oftherocks.Abouthalfofthegemmineralsare
alsocomposedwhollyofthesesame8elements.Ifweexpandthelisttothe20most
abundantelements,allbut6areincludedthataremajorconstituentsofminerals
normallyproducinggem-qualitymaterials.These20elementsarelistedinTable2in
orderofdecreasingabundanceintheearth'scrust.Alsolistedareafewoftherarer
elementseitherpresentingemmineralsorotherwiseofinteresttothegemologist.
Whenoneoftherarerelementsispresentinmorethantraceamounts,itindicates
thatsomenaturalprocesshasbroughtaboutaconcentration.Suchconcentrationdo
occur,resultinginrareandunusualminerals,andtheirexplanationformsa
fascinatingchapterinthescienceofgeochemistry.Gemvarietiesofsomeofthese
minerals,althoughrare,mayinplacesoccurinappreciableamounts.Thus,in
consideringtheoriginofgemminerals,wemustaccountforboththeunusual
conditionsunderwhichthecommonelementsarebroughttogetherandthesignificant
concentrationsofminorelements.
13
Table2AbundanceofEementsinEarth'sCrust
TwentyMostAbundantElementSomeLessAbundantElement
ElementSymbolWt.%ElementSymbolWt.%
Oxygen06.60ChromiumCr0.010
SiliconSi27.72NickelNi0.008
AluminumAl8.13ZincZn0.0065
IronFe5.00CopperCu0.0055
CalciumCa3.63CobaltCo0.0025
SodiumNa2.83LithiumLi0.0020
PotassiumK2.59NitrogenN0.0020
MagnesiumMg2.09LeadPb0.0013
TitaniumTi0.44BoronB0.0010
HydrogenH0.14ThoriumTh0.0007
PhosphorusP0.10CesiumCs0.0003
ManganeseMn0.09BerylliumBe0.00028
FluorineF0.063TinSn0.00020
BariumBa0.040Uraniumu0.00018
StrontiumSr0.03
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