Xie Rehren 2009 Lead Silver Slag China BUMA VI

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Scientificanalysisoflead-silversmeltingslagfromtwositesinChinaPengfei Xie and Thilo Rehren

abstract Thispaperpresentsdataontwosetsoflead-silverslagsamplesfromnorthernandsouth-westChina.Atpresent,veryfewslagstudiesonancientandhistoricslagsfromChinaareavailableinEnglish,andthesetwositesinparticulararecompletelyunstudied.Thesitesandslagswereselectedontheassumptionthattheyrepresentlead/silverproduction.Thispapershowsthetechnologicalrangeofslagsrelatedtotheproductionofthesetwomet-als,andwhattechnologicalinformationcanbegainedfromtheirstudy.Itishopedthatthispaperwillcontributetoknowledgeaboutancientandhistoricsmeltingpractices,byofferingnewandoriginaldata,andbycomparingthefindingsfromthesesitestootherpublishedsites.

Introduction

Leadandsilveraretypicallyseenasverydifferentmetals.Leadisconsideredcheapandoflittlefunctionaluseapartfrominarchitectureandasametallurgicaladditiveincer-tainbronzes.Silverincontrastisoneofthepreciousmet-als,desiredbymankind for itsbeauty,valueand relatedfunctionssuchasjewelleryandcoinage.Despitethisseem-inglydisparatenature, their ores often coexist innature,andthesmeltingproceduresofthetwometalsarecloselyrelated.Due to these natural affinities, they usually alsoappearedtogetherinancientChinesetexts,andeventodaytheirproductioncanonlybefullyunderstoodwhenstud-iedtogether.

Silverdoesoccurinnatureasapureor‘native’metal,andseveralrichsilvermineralshavebeenexploitedinthepast,mostlysulphidesofsilvertogetherwithvariablequan-titiesofothermetals,suchascopper,antimonyorbismuth.However,thebulkofprehistoricandhistoricsilverproduc-tionisbasedonthesmeltingofsilver-containinggalena,lead sulphide.The silver concentrations in galena rarelyexceed0.5%byweight,andevenatconcentrationsaslowas0.1wt%,thevalueofthesilvercontentisoftenhigherthanthatoftheleadmetal.Smeltingsuchmixedorewillnotseparatethetwometals;instead,alead-silveralloy,orbullion,will be produced.A second step is necessary toseparate the twometals.During this cupellation the lessnoblemetal(lead)isoxidisedduringre-meltinginanopenhearth,whilethenoblemetal(silver)remainsinitsmetal-licstate.Thus,attheendofthecupellationprocessallleadispresentasleadoxide,orlitharge,whichcanbemechani-callyseparatedfromthesilvermetal.Thelithargecantheneasilybere-smeltedtoleadmetal,formingsoftleadwithlessthanc.100ppmsilver.Largequantitiesofleadmetalare

thereforeproduced(oftenmorethan100timestheweightof the silver).Archaeological evidence of such smeltingsitescouldincludetheslagfromthefirstsmelting,possi-blylithargeremains,andfurnacefragments.Thescientificstudyoftheseremainscanoffermuchinformationaboutthetechnologicalprocesses,whileevidenceofcupellationalsorevealstheeconomicrelationshipbetweenthetwometals.

TheslagsamplesstudiedwerecollectedbyProfessorKoandProfessorLiYanxiangoftheUniversityofScienceandTechnologyBeijingfromtwoChinesesites:TangcountyandShizhucounty.TheTangcountyofHebeiprovinceislocatedinnorthernChina,190kmsouth-westofBeijing.TheShizhucountyofChongqingmunicipalityissituatedinsouth-westChina,withtheYangtzeRiverwindingacrossitswesternborder.Historically,thetwositeshadabundantdepositsofmineraloresoflead,silver,ironandgold.Theybothboastalonghistoryofminingandsmelting.

Untilnow,noformalarchaeologicalexcavationhasbeencarriedoutatthesesites,andnoscientificanalyticalstudyhasbeenmadeoftheslagandceramicspecimensfromthetwoareas.Ourresearchendeavouredtoundertakescientificanalysisofaninitialselectionofspecimensfromthetwositesusingopticalmicroscopy,scanningelectronmicros-copywithenergy-dispersivespectroscopy(SEM–EDS)andX-rayfluorescence(XRF).Thispaperpresentstheresultsoftheslaganalyses.

Methodology

In the sampling process, the specimens were separatedintotwogroups:groupT1forsiteno.1(Tangcounty)andgroupS2forsiteno.2(Shizhucounty),andthenlabelled

Offprint from J. Mei and Th. Rehren (eds), Metallurgy and Civilisation: Eurasia and Beyond Archetype, London 2009. ISBN 1234 5678 9 1011

PENGFEIXIEANDTHILOREHREN

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T1A,T1B,T1C,T1D,T1E,T1FandS2A,S2B,S2C,S2D,S2Erespectively.Afterphotographicdocumentation,pol-ishedblockswereproduced for further analysis.SamplepreparationforopticalmicroscopeandSEM–EDSanaly-sesincludedcutting,mounting,grinding,polishingusingstandardmetallographicprocedures,andcarboncoatingtopreventachargebuildupfromtheelectronbeamduringSEM–EDS analysis. In contrast, sample preparation forXRFanalysis involvedcutting, crushing,milling topro-duceahomogenouspowder,whichwasthenmixedwithwaxandpressed intopellets.TheequipmentusedwasaLeica DMLM reflected light metallographic microscopeequippedwithadigitalcamera,aHitachiS-570SEMwithanOxfordINCAEDSsystemandaSpectroXLab2000X-rayfluorescencespectrometer.Thetechniqueswerecom-plementary, serving different purposes. SEM–EDSgivesfarbetterresultsformajorelementsinasinglephasethanXRFduetothegoodspatialresolution,whileXRFismoreusefulfordetectingminorandtraceelementsinthebulkmaterial(<0.1wt%).

Results and initial interpretation

The11analysedspecimensandtheresultswithsomeini-tialinterpretationsarepresentedbelow.Toavoidrepetitionin thepresentationofanalytical results, thedataarepre-sentedingroups.Onlyrepresentativesamplesareconsid-eredbelow.AnoverviewofhistoricalsourcesrelatingtosilversmeltinginChinaisgiveninXie(2005).FulldetailsoftheanalysesandresultsofouranalysesarepresentedinXie(2006).

Tang county

ThemacroscopicappearanceofsampleT1Aisdarkblackwith theflow textureon thesurface, suggesting itmightbe tapping slag (Fig. 1). This sample is representativeof themajorityoffindsstudiedhere, includingT1DandT1F,althoughwecannotjudgehowrepresentativeitisforthe entire assemblageon site.Themetallographic imageshows that sampleT1A isdominatedbyaglassymatrixwithnumeroustinybrightmetallicspots,andafewcrys-tals,bubblesandpores.Thelightergreycircularfeaturesintheslagglassarenoteworthy.SEM–EDSanalysisdidnotrevealanycompositionaldifferencebetweenthesurround-ingglassymatrixandthecircularfeatures;manyofthemcontainasmallinclusionorprillintheircentre.Weinter-pretthesecircularfeaturesasdevitrificationspheresaroundsome crystal nuclei, causedby a relatively slowcoolingof the slag (Fig. 2). Similar features havebeennoted inglassycrucibleslaginearlyIslamicUzbekistan(Rehrenet al.forthcoming).

ThechemicalcompositionoftheseslagsasdeterminedbySEM–EDSandXRFisgiveninTable1(mainoxides)andTable2(traceelements).Themaincomponentsoftheseslagsaresilica(55–65wt%),around15wt%ironoxide,5–10wt%lime,andloweramountsofalumina(6–8wt%)

andmagnesia(2–4wt%).SampleT1Dishigherinsilicathantheothersamples;thisisduetonumerousinclusionsofquartzparticlesintheslag.Theseinclusionsarepartlyabsorbedinthesurroundingglass,andhavenumeroussul-phideprillsintheirstructure,whichappeartoberesidualorematerial.SEM–EDSanalysesofthemeltphasebetweenthequartzinclusionsindicateasilicaconcentrationofc.58wt%, in linewith thebulkcompositionof theotherslagsamplesinthisgroup.Suchacompositionisinagreementwiththepredominantlyglassycharacteroftheslagasseenintheopticalmicroscope,andrelativelytypicalforahigh-temperature,stronglyreducingfurnaceregime.Duetothecomplexchemistry,itisdifficulttoestimatetheactualproc-esstemperature;testfiringswouldbenecessarytodeter-minetheliquidustemperature.

Onlya few inclusionswere found largeenough tobeanalysed.They included leadmetalprillswithup to2%silver,nearlypuresilverprills,andcomplexsulphidesrichinleadandiron,oftencontainingupto1%silver.

Figure 1SlagsampleT1A:typicalflowstructuresurface(centre).

Figure 2SlagsampleT1A:devitrificationspheres(lightgrey)inaglassyslagmatrix(widthofimagec.1mm).

SCIENTIFICANALYSIS OFLEAD-SILVERSMELTINGSLAGFROMTWOSITES INCHINA

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Forourinvestigationitisparticularlyimportanttonotethepresenceofbetween0.4and2wt%eachofzincoxideandleadoxide,indicatingthatthesearenon-ferrousslags.The very low level of copper (Table 2, 200–400 ppm)suggeststhatthisisnotcopperslag,butindeedleadslag.Furthermore, the presence of relatively high silver con-centrationsinbothmetalandsulphideprillssuggeststhattheproducedmetalwasasilver-richbullion,andthattheeconomicinterestinthissitewasprimarilysilverproduc-tion.This is furtherconfirmedby thepresenceofcupel-lation remains at this site (to be presented in a separatepublication).

The macroscopic image of sample T1C differs fromthe previous group in that it shows twodifferent layers:aceramiclayeratthetopandaslaglayeratthebottom.Theslaglayerisdarkerthantheceramiclayer,whiletheceramic layer ismoreporous than the slag (Fig.3).ThemicrographofsampleT1Cshowsanumberofsmallcracks

intheglassymatrixthatwerebreakingupduringpolishing.Weinterpretthistoshowthattheglasshasaconsiderableamountofresidualtensioninitfromthecoolingphase.Inaddition,thissampleshowsdevitrificationspheressimilartotheprevioussample.Thebrightinclusionsintheslagareleadsulphideandleadandsilvermetalprills.Theyareallverylowincopperoriron.

Theceramicattachedtothisslagsamplehasbeenana-lysedbySEM–EDS;theaverageoffivedifferentareameas-urementswas60.2wt%silica,28.9wt%alumina,3.7wt%ironoxide,andaround2.5wt%eachoflimeandpotash,plus1.6wt%titania,andlessthan1wt%magnesia.Thisisahighlyrefractoryceramicbasedonakaoliniticclayandrichinquartzinclusions.Theshapeoftheceramicistubu-lar, althoughnotenoughwaspreserved todetermine thediameter.Thisisinterpretedasafragmentofatuyèrefilledwithsomeslagwhichwaseitherdeliberatelytappedthroughit,orwhichoverflowedintothetuyèrewhenthefurnaceoverflowed.Similarslag-filledtuyèresarewellknownfromAfricanironsmeltingsites,andseemtobearegularpartoftheprocessratherthananindicationofamalfunction.

Samples T1B and T1E have a very different macro-scopic appearance,microstructure andcomposition fromtheremainingsamplesofthissite(seeTables1and2).Theyaremoreporous,almost frothy (Figs4and5),andhavemanyinclusionsofahardwhitealloy.AccordingtoSEM–EDSanalysis, these inclusionsare iron-basedwithmorethan95wt%iron(Figs6and7);thebalanceismostlikely

Sample Na2O MgO Al2O3 SiO2 P2O5 SO3 K2O CaO TiO2 MnO FeO ZnO PbOT1A – 4.3 6.4 55.2 0.4 0.8 1.5 11.1 – 1.5 16.9 1.9 0.4T1C – 4.5 6.3 55.5 0.3 0.7 1.3 10.9 0.3 1.6 16.7 1.9 0.4T1D – 2.0 6.8 64.7 0.2 0.1 1.6 4.7 0.3 0.7 16.7 0.4 2.2T1F – 3.8 7.7 58.7 0.3 0.7 2.7 9.1 0.2 2.9 12.5 1.0 0.4T1B 1.5 2.0 14.1 61.3 – – 2.7 12.8 0.7 0.5 4.4 – –T1E 0.3 22.7 7.5 49.7 – – 1.7 14.9 0.2 0.8 2.2 – –(P)ED-XRFdata,quantifiedbytheTurboquantmethod.Datanormalisedto100wt%.

Table 1

Sample Pb Cu Sr Zn Ag Ba SbT1A 4200 200 230 – 15 1400 –T1C 4000 190 220 – 15 1150 –T1D 22000 360 200 3800 220 260 80T1F 4000 310 385 – 10 1850 –T1B 10 15 760 25 – 750 –T1E 5 15 350 15 – 280 –(P)ED-XRFdata,quantifiedbytheTurboquantmethod.

Table 2

Figure 3SlagsampleT1C:ceramic layer(top)surroundingaslagcore(darkergrey).

Figure 4IronslagsampleT1B:aporousmacrostructure.


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carbon.Chemicalanalysisshowsthatthisslaghasverylowlevelsofbasemetalsandalsoverylowironoxideconcen-trations,buthighlime,magnesiaandsilica.Thisisclearlynotabasemetalslag;thechemicalandstructuralcomposi-tionandthenumerousiron-richprillsaremorecharacter-isticofblastfurnaceironslag.Intriguingly,thechemistrydiffersconsiderablybetweenthetwosamples:T1Eisveryrichinmagnesia,withmorethan20wt%,whileT1Bhasonlyone-tenthofthis,butamuchhigheraluminalevel.T1Bisalmostentirelyglassy,whileT1Eisrichincrystalswithabout45wt%MgO,42wt%SiO2and11wt%FeO,butverylittlelimeandotheroxides.Thisindicatesanapproxi-mate formulaofMg2SiO4withsomesubstitutionof ironoxideformagnesia,i.e.aforsterite-richolivine.

Thus, among the few samples analysed is evidenceforbothlead-silversmeltingandforironsmeltingatthissite.Bothprocessesseemtobedrivenbyablastfurnacetechnology, but are clearly based on different ores. It isimpossibleatpresenttosaywhethertheyaretechnicallyorchronologicallyrelated,orwhethertheyarecompletelyindependentfromeachotherandonlyappeartogetherherebycoincidence.

Shizhu county

Theslagsfromsiteno.2aremostlytapslagswithclearflowstructures(Fig.8).Therearesomegreenandbrowncor-rosionfeaturesvisible.Noceramicfragmentsareattachedtotheseslags.

ThemicrographofsampleS2Ashowsclearevidenceoftapping.Figure9illustratesaquenchingzonenearthesur-facewheretheslagquicklysolidifiedasaglass,whileinthecentre,wherethecoolingratewouldhavebeenslower,it has formed crystals. The micrograph of sample S2B (Fig.10)showsamagnetiteskinseparatingtwosubsequenttappinglayers.Suchamagnetiteskinformsonlywhenslagflowsintoairatambienttemperature,i.e.outsidethefur-

(a)

Figure 5IronslagsampleT1E:analmostfrothymacrostructure.

Figure 6Micrographof iron slagT1E: calciumsilicate inclusions(grey)inaglassymatrixwithnumerousmetallicprills(bright)andabundantporosity(black)(widthofimagec.2mm).

Figure 7IronslagsampleT1E:close-upofametalprillshowinganiron-ironcarbonalloystructure(widthofimagec.0.2mm).

Figure 8SlagsampleS2B:cleartappingstructure.


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Figure 9MicrographofslagsampleS2D:theglassyquenchedouterregion(bottom)andthemorecrystallineinnerpart(widthofimagec.1mm).

Figure 10MicrographofslagsampleS2B:amagnetiteskin(lightgrey,centre)separatingtwosubsequentslagflows(widthofimagec.1mm).

Figure 11(a)MicrographofslagsampleS2B:typicalstructurerichinsulphideinclusions(bright),andvarioussilicatecrystals(differentgreyshades)inaglassymatrix.(b)MicrographofslagsampleS2A:severaldifferentsilicatephasesinaglassymatrixtogetherwithnumeroussulphideinclusions(bright)(widthofimagec.0.2mm).

Figure 12(a)MicrographofslagsampleS2E:thesilicateslagphase(left,dark)andthelargemetallicpart(right,bright)(widthofimagec.1mm).(b)detailofthemetallicpartinthesamesampleshowingacopper-richmatrixandvariouscopper-arsenicphases(differentgreyshadesandcrystalshapes)(widthofimagec.0.1mm).

(a) (b)

(a) (b)


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nace.Incontactwiththeoxygenoftheairsomeoftheironintheslagnearthesurfaceissufficientlyoxidisedtoformmagnetitecrystals.Thisskin is thencoveredby thenextflowofslagandisthereforepreservedinthecontactzonebetweenthetwoflows.Often,thesetwoflowsexhibitdif-ferentcrystalsizes,duetodifferentcoolingspeeds.

The samples have different amounts of sulphide andmetalinclusions(Fig.11).Theyalsohavevarioussilicatecrystals,mostlypyroxeneandbarium-richfeldspars,andaremoreporousthanthepreviousgroupofleadslags.Theirchemicalcompositiondifferssignificantly;theyarericherinironoxide(35–40wt%)andhavemuchlesslime(lessthan5wt%).Inaddition,threehavehighlevelsofleadoxide (2wt%PbO)andzincoxide(3wt%ZnO),whilethefourthhas only 0.3wt%PbO and 0.9wt%ZnO.High bariumoxidelevelsaremostcertainlyduetothepresenceofbaryte(BaSO4)asaganguemineral,atypicalcomponentofmanyleadores.Allsamplescontainedmetalandsulphideprills;inS2A theseweremostly ironarsenide (70–90wt%Fe,10–30wt%As)andlowamountsofcopperandantimony,whilethesulphideswerepredominantlyleadsulphide.InsampleS2Bweonlyfoundleadsulphideinclusions,whileinsampleS2Dasinglegoldprillwasfound(91wt%Au, 8wt%Feand1wt%Zn),andnumerouslead-ironsulphideprills.Overall,itisreasonabletoassumethatthethreesam-plesS2A,BandDareallleadsmeltingslags,althoughthepresenceofdifferentmetallicphasesindicatesthattheorewasrelativelycomplex,andthatothermetalscouldhavebeenproducedaswell.ThereislessindicationhereforthepresenceofsilverintheslagscomparedtotheTangcountysite;nofragmentsoflithargeorothercupellationremainswerefoundduringfieldwork.

However, in viewof the complex compositionof theleadslagsinthisgroupitisnotsurprisingtonotethattheothertwosamplesfromthissite,S2CandE,areconsider-ablyricherincopper(3–6wt%)anddifferinotherdetails,too.Theiroverallchemicalcharacteristicsarequitesimi-lar though,with a high barium content and very similarironoxideandlimelevels.SampleS2Ccontainednumer-ousmetalandsulphideprills:someprillshadanaveragecompositionof90wt%Pb,7wt%Cuandafewpercentarsenic;otherswere70wt%Cuand30wt%As;yetoth-erswerenearlypureironmetalwithalowcoppercontent.Thesulphideinclusionswerebothlead-andcopper-rich.SampleS2Ehadahugemetallicprilltrappedinit;SEM–EDSanalysisgaveanaveragecompositionofabout70wt%Cu,15–20wt%As,5–8wt%Fe,andminorquantitiesoflead,sulphur,antimonyandzinc.Occasionally,individualsmallprillsintheslagS2Ewereidentifiedasbeinglead-oriron-dominated,butalwayswithahighcoppercontent.Overall,weinterpretthesesamplesascopperslag,possi-

blyexploitingthesameoredepositbutobtainingdifferentmineralsfromit.

Thus,wesee twodifferent,butclosely relatedmetal-lurgical processes here: one smelting leadmetal and theotherarsenicalcopper.ThehighbariumcontentofsamplesS2CandS2Ematchesthecopperslagcompositioninlate

Sample MgO Al2O3 SiO2 P2O5 SO3 K2O CaO TiO2 FeO CuO ZnO BaO PbOS2A 1.1 6.8 34.4 0.2 3.5 1.2 3.8 0.8 33.3 – 3.1 9.8 1.5S2B 1.1 6.7 33.9 0.2 3.0 1.1 4.1 0.8 34.3 – 3.3 9.5 1.8S2D 1.7 5.5 32.8 0.1 2.0 0.8 4.5 0.5 40.4 – 3.4 6.0 2.0S2C 0.8 3.0 21.5 0.1 9.2 0.3 1.5 1.0 40.8 6.4 0.9 12.3 0.3S2E – 2.2 23.0 – 5.7 – 1.5 – 42.7 2.9 0.9 20.6 –(P)ED-XRFdata,quantifiedbytheTurboquantmethod.Datanormalisedto100wt%.

Table 3

Sample Cu Sb Sr AsS2A 1100 75 1300 3200S2B 950 30 2000 1100S2D 830 25 1100 1350S2C 70000 – 1150 3700(P)ED-XRFdata,quantifiedbytheTurboquantmethod.

Table 4

prehistoricXinjing(Mei2000:52).Theyalsoshowhighcopperandarsenicconcentrations,andmanyinclusionsofcopper-arsenicalloy(Fig.12).Itislikelythattheseslagsoriginatefromthesmeltingofacomplexore,andthatbothleadandcopperwereproduced.Atthisstage,itappearsasifthereweretwophysicallyseparateoperations,andnotajoint lead-coppersmeltingprocess.However,moreworkandexcavationwouldbenecessarytoclarifythistechnicalaspect.Furthermore, it isuncertainwhether thesmeltingalsoincludedtheproductionofsilverorwhetherthiswaspredominantlyabasemetalmetallurgy.

From the above analyses, we summarise that samplegroupS2consistsofthreelead(silver?)slagsamples,andtwoarsenicalcopper(lead?)slagsamples.Thethreeleadslagsamples(S2A,S2BandS2D)aremostlyglassyandhaveonlysmallmetalorsulphideinclusions,whilethetwocopperslags(S2CandS2E)appear lessglassyandhavemanymoremetalandsulphideinclusions.Sofar,nofirmevidenceforsilverproductionhasbeenfoundamongtheslagsfromthissite.

Conclusions

Through scientific analysisof11 slag samples from twosites,wefindthatsevenareleadandpossiblylead/silversmeltingslags,twoareironslags,andtheremainingtwoarecopperslagsfromamixed(arsenic)copper-leadore.

Ifwecomparethecompositionofthelead-silverslagsfromthetwosites(seeTables1and3),wefindthatincon-sidering themajorelements,groupS2slagshavehigherconcentrationsofFeO,BaO,ZnO,SO3,TiO2andAs2O3thangroupT1,whilegroupT1slagshavehigherlevelsofSiO2,MgO,CaOandMnO.Amongthetraceelements,groupS2


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sampleshavemuchhigherconcentrationsofcopper,arsenicandstrontium,whilegroupT1samplesshowhigherlevelsofsilver.Thesedifferenceswereclearlycausedbydifferentoredepositsandspecificallyadoptedsmeltingprocesses,aswouldbeexpectedfromtheirdifferentgeologicalorigin.

FromtheTangcountysitethereisevidencefortheuseoftuyèrestoblowairintothefurnaces.Theyaremadefromahigh-qualityrefractoryclayandwouldhavelastedalongtimeevenathightemperatures.Itisassumedthattheyfilledwithslagwhentheblowingstoppedattheendoftheproc-essandtheslaglevelhadincreasedinthefurnace.Morefieldworkisnecessarytoinvestigatethisaspectfurther,bylookingatfragmentsoftuyèreswithoutslagfillingandpos-sibleotherfurnacefragmentsthatwouldprovideimportantinformationaboutthefurnacetype.Furtherarchaeologicalworkisalsonecessarytodatethemetallurgicalactivitiesatbothsites.

LeadsmeltinginChinabeganveryearlyandthemetalwasmass-producedintheChineseBronzeAgetomeettheenormousdemandforlead-containingbronzeobjects(Sunand Li 2003).Archaeological excavations have demon-stratedthatasearlyastheShangdynasty(16th–11thcen-turyBC),theChinesepeoplewereabletomakealmostpureleadmetal(Li1984).However,itisnoteworthythatalltheslagsstudiedherearefromatypetypicalofadvancedblastfurnacetechnology,asisknownfromancienttextandillus-trations(seealsoMeiandRehren2005).

EarlyleadslagsareknownfromnumeroussitesinancientEurope;fromtheBronzeAgethroughtheRomanperiodandtheMiddleAgesintotheearlymodernperiod.Thispapercannotgiveacomprehensiveoverviewoftheirchemistryandmineralogybutsufficeittosaythatleadslagsarefarmore variable in their appearance and composition thantypicalcopperorironslags,reflectingthewiderchemicalvariabilityofleadoresandtheassociatedgangueminerals.Theclosestparallelsintermsofbulkcomposition,glassyappearanceandstronglyreducingconditionsarefromvari-ousmedieval to earlymodern sites in theSchwarzwald,south-west Germany (Goldenberg 1994), thought to bebasedonawater-poweredblastfurnacetechnology.

Ofparticularinterestistheevidenceformultiplemetal-lurgicaloperationsatbothsites.InTangcounty,thelead-silver slag ismixedwith typical iron blast furnace slag;themacroscopicandmicroscopicappearanceofbothslagsissosimilarthatitcanbeassumedthatverysimilarfur-naceswereemployedintheirproduction,eventhoughtheir

chemicalcompositionissignificantlydifferent,asbefitsthesmeltingoftwosuchdifferentmetals.IntheShizhucountysite,tworelatedmetalswereproduced:leadandcopper.Wecanspeculatethattheycamefromthesameoredeposit,butmayhavebeensmeltedseparately.Clearly,thesesiteshaveahugepotentialforfurtherarchaeologicalandarchaeomet-allurgicalwork.

Acknowledgements

WewouldliketoexpressourgratitudetothelateProfessorP.UckooftheUCLInstituteofArchaeology,whoasExecutiveDirectorofthe InternationalCentre forChineseHeritageandArchaeology fa-cilitatedPengfeiXie’sstudyatUCL;theInstituteofHistoricalMet-allurgyandMaterialsofUSTB,andinparticularProfessorKoandProfessor Li Yanxiang, for permission to study the material; and DrMarcosMartinón-Torres,SimonGroomandKevinReevesoftheUCLInstituteofArchaeologyfortheirgeneroushelpinvariousas-pectsofthisresearch.

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ForewordbyWeidongLuo,Chancellor,UniversityofScienceandTechnologyBeijing viiForewordbyRobertMaddin,ChairmanoftheBUMAStandingCommittee ixPreface xiAcknowledgements xiiiListofcontributors xviiIntroduction xxi

Early metallurgy across Eurasia

AncientmetallurgyintheEurasiansteppesandChina:problemsofinteractions 3EvgenijChernykh

EarlymetallurgyinChina:somechallengingissuesincurrentstudies 9JianjunMei

MetaltradeinBronzeAgeCentralEurasia 17LiangrenZhang

Documentaryandarchaeologicalevidenceforanantiquecopper-nickelalloy(baitong) 26productioninsouthernChinaanditsexportationtoIndiaFrançoisWidemann

MetaltradebetweenEuropeandAsiainclassicalantiquity 35AlessandraGiumlia-Mair,MichelJeandinandKen’ichiOta

TheblackbronzesofAsia 44PaulCraddock,MaickelvanBellegem,PhilipFletcher,RichardBlurtonandSusanLaNiece

Bronze casting technologies in ancient China

OriginsandevolutionofthecastingtechnologyofAnyangbronzeritualvessels:anexploratorysurvey 55YuLiu

ThreeWesternZhoubronzefoundrysitesintheZhouyuanarea,Shaanxiprovince,China 62WenliZhou,JianliChen,XingshanLei,TianjinXu,JianrongChongandZhankuiWang

Newresearchonlost-waxcastinginancientChina 73WeirongZhou,YaweiDong,QuanwenWanandChangsuiWang

IncipientmetallurgyinYunnan:newdataforolddebates 79TzehueyChiou-Peng

Contents

METALLURGYANDCIVILISATION:EURASIAANDBEYOND

vi

AstudyofthesurfacecraftofweaponsfromtheBa-ShuregionofancientChina 85ZhihuiYaoandShuyunSun

ProductionofsignatureartifactsforthenomadmarketinthestateofQinduring 90thelateWarringStatesperiodinChina(4th–3rdcenturyBCE)KatherynM.Linduff

Ancient iron and steel technologies in Asia

Anearlyiron-usingcentreintheancientJinstateregion(8th–3rdcenturyBC) 99RubinHanandHongmeiDuan

FromwesternAsiatotheTianshanMountains:ontheearlyironartefactsfoundinXinjiang 107WuGuo

SouthIndianIronAgeironandhighcarbonsteel:withreferencetoKadebakeleand 116comparativeinsightsfromMel-siruvalurSharadaSrinivasan,CarlaM.Sinopoli,KathleenD.Morrison,RangaiahGopalandSrinivasaRanganathan

SurvivaloftraditionalIndianironworking 122VibhaTripathiandPrabhakarUpadhyay

Finestructures:mechanicalpropertiesandoriginofironofanancientsteelsword 129excavatedfromanoldmoundinJapan MasahiroKitada

Specialisationiniron-andsteel-makingintheearlyMiddleEastandCentralAsia: 134myths,assumptionsandareassessmentofearlymanuscriptevidence BrianGilmourAncient metallurgical and manufacturing processes

Theearlyhistoryoflost-waxcasting 147ChristopherJ.Davey

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