Radiocarbon dating of pearls: Michael S. Krzemnicki 1, Irka Hajdas 2, Georges Bonani 2 Lukas Wacker 2 1 SSEF Swiss Gemmological Institute, Switzerland, 2 Laboratory of Ion Beam Physics, Radiocarbon Dating, ETH Zurich, Switzerland 21 st International Radiocarbon Conference Paris, 9-13 July 2012 Pearl: Product of biomineralization Columnar calcite Aragonite CaCO3 (orthorhombic) Tabular aragonite Calcite CaCO3 (trigonal) 1
Natural pearls versus cultured pearls Naturalpearlsareformingaccidentallyandwithoutanyhuman interventioninawildshell,livinginitsnaturalhabitat. Culturedpearlsareproducedinmolluscsinapearlfarm,eitherwitha shellbeadinthecentreorwithoutbead. Cultured pearls from Indonesia 2
Bahrain und Qatar 2010 Visit of the impressive pearl exhibition in Qatar, Verdana, 10pt, normal Radiocarbon Dating of Pearls: as an additional method to distinguish between natural and cultured pearls 1900 2000 Onlynatural pearlsinthe trade CulturedpearlsMarketshare Pre1900 Girst attemps forpearl cultivation (mostly Mabé)in Japan, Australia, Europe 1916 Mikimoto beaded saltwater cultured pearls. Pinctada( fucata( Southern Japan 1960 beaded saltwater cultured pearls. Pinctada( maxima( Northern Australia 1980 beaded saltwater cultured pearls. Pinctada( margaritifera( French Polynesia 1983 Chinese beadless freshwater cultured pearls. nio( 2008 Keshi beadless saltwater cultured pearls. Pinctada( maxima( 2009 saltwater cultured pearlswith natural pearlbeads Pinctada( maxima( 3
Recent shells: ShellfromPinctada(radiata((Orient( pearl(oyster)(fromthearabiangulf, personallycollectedin2009. OneSigma [1954.50(Jul)1954.81(Oct)]0.127141 [1998.10(Feb)2000.06(Jan)]0.872859 TwoSigma [1954.28(Apr)1955.05(Jan)]0.150058 [1997.12(Feb)2000.80(Oct)]0.849942 Note:300yearsofINTCAL04datahavebeen prependedtothisdataset Calibrationof1.099000±0.003000withLevin 14 Cdataset Smoothing:1.000000 I.LevinandB.Kromer(2004)Thetropospheric 14 CO 2 levelinmidlatitudesofthenorthernhemisphere.radiocarbon 46(3):12611272. I.Levin,S.Hammer,etal.(2008)RadiocarbonobservationsinatmosphericCO2:DeterminingfossilfuelCO 2 over EuropeusingJungfraujochobservationsasbackground.ScienceoftheTotalEnvironment391:211216. Recent shells: ShellfromPinctada(maxima( (Silverlip(pearl(oyster)(fromthe Philippines,collected1990(pers. comm.h.a.hänni) OneSigma [1959.61(Aug)1959.81(Oct)]0.092576 [1989.67(Sep)1992.10(Feb)]0.907424 TwoSigma [1959.47(Jun)1960.07(Jan)]0.118790 [1988.98(Dec)1992.65(Aug)]0.881210 Note:300yearsofINTCAL04datahavebeen prependedtothisdataset Calibrationof1.162000±0.004000withSH1.14cdataset Smoothing:1.000000 QHuaandMBarbetti(2004)ReviewofTroposphericBomb 14 CDataforCarbonCycleModelingand AgeCalibrationPurposes,Radiocarbon46:12731298 4
Recent shells: OneSigma [1958.76(Oct)1959.31(Apr)]0.228138 [1960.03(Jan)1960.91(Nov)]0.365475 [1983.87(Nov)1984.62(Aug)]0.406388 TwoSigma [1958.50(Jul)1961.26(Apr)]0.617661 [1983.61(Aug)1985.05(Jan)]0.382339 Note:300yearsofINTCAL04datahavebeen prependedtothisdataset Calibrationof1.215000±0.0040000withLevin 14 Cdataset Smoothing:1.000000 I.LevinandB.Kromer(2004)Thetropospheric 14 CO 2 levelinmidlatitudesofthenorthernhemisphere.radiocarbon 46(3):12611272. I.Levin,S.Hammer,etal.(2008)RadiocarbonobservationsinatmosphericCO2:DeterminingfossilfuelCO 2 over EuropeusingJungfraujochobservationsasbackground.ScienceoftheTotalEnvironment391:211216. ShellfromPinctada(radiata((Orient( pearl(oyster)(fromthearabiangulf, collectedin1990(pers.comm H.A.Hänni). Recent pearl Beadlesssaltwaterculturedpearl,Keshitype Pinctada(maxima,(Indonesia ~2000AD 5
Recent pearl Beadless freshwater cultured pearl nio, China ~ 2000 AD Pearl before bomb peak Saltwaternaturalpearl NovaScotia,Canada ~1950?? 6
Case study from a client: Natural or cultured pearl? Sinceabout2009:culturedpearls withnaturalpearlasbead Conclusion: Naturalpearl,ascultivation methodsforpinctadamaxima pearlswithnaturalpearlswere notdevelopedbefore2009. ETH46319: 365±30BP 68.2%probability 1450AD(45.9%)1530AD 1570AD(22.3%)1620AD 95.4%probability 1440AD(51.5%)1530AD 1540AD(43.9%)1640AD Calibrated*C14*ages*(Calendar*time*intervals)*using*OxCalv3.10* INFORM:ReferencesAtmosphericdatafromReimeretal(2009);** OxCalv3.10BronkRamsey(2005) 7
Radiocarbon Dating of Pearls: To support the documented historical provenance of a pearl. Renaissance necklace with pearls 8
La Peregrina Pearl soldfor11mios$atchristie sauctioninnewyork,dec.2011? 9
Historic pearls: PearlsfromPinctada(radiatafrom thearabiangulf,probablyfrom 1860(pers.Comm.T.Faerber, Geneva) ETH46322: 130±30BP68.2%probability 1680AD(20.9%)1740AD 1750AD(1.1%)1770AD 1800AD(7.8%)1820AD 1830AD(27.0%)1890AD 1910AD(11.4%)1940AD 95.4%probability 1670AD(37.9%)1780AD 1790AD(57.5%)1950AD Calibrated*C14*ages*(Calendar*time*intervals)*using*OxCalv3.10* INFORM:ReferencesAtmosphericdatafromReimeretal(2009);** OxCalv3.10BronkRamsey(2005) Historic freshwater shell 2200BP 2100BP 2000BP 1900BP 1800BP 1700BP 1600BP Atmospheric data from Reimer et al (2004);OxCal v3.10 Bronk Ramsey (2005); cub r:5 sd:12 prob usp[chron] PC14_6b : 1930±35BP 68.2% probability 25AD ( 9.1%) 40AD 45AD (40.3%) 90AD 95AD (18.8%) 125AD 95.4% probability 40BC (95.4%) 140AD Freshwatershell Switzerland ~1910 2200CalBP 2000CalBP 1800CalBP 1600CalBP Calibrated date Problemof old agesduetounknowncorrection forcarbonreservoir. 10
Conclusions Firstresultsonalimitednumberofsamplesshowthatradiocarbonage datingofpearlsispossible. Radiocarbondatingmayresultinadditionaldata(usingthebombpeak) whichenablesaunambiguousdistinctionbetweenculturedandnatural pearls. Radiocarbondatingofhistoricpearlsmustbefurtherinvestigatedwithwell documentedsamples. Extractionmethodstoavoiddestructionofpearlshavetobefurther developedbyminimisingthesampleweight. Formostpearls,thegeographiclocalitywheretheyformedisnotknownor onlyvaguely.thisresultsinproblemswhencorrectionsforthecarbon reservoiragesarerequired. Ingeneral,freshwatershellsandpearlsgive fancy ages(carbonreservoir). Thank you for your attention Acknowledgements: ThomasFaerber,Geneva, JoséCasares(Shanghai Gems),Geneva, HenryA.Hänni(GemExpert), Basel;ImuraDaiji(RAK Pearls),RasAlKaihmah; AndyMuller(Hinata Trading),Kobe,Japan, A.R.Mahmood,Bahrain. 11