The trade of glass beads in early medieval Illyricum: towards an Islamic monopoly PDF
Preview The trade of glass beads in early medieval Illyricum: towards an Islamic monopoly
ArchaeologicalandAnthropologicalSciences(2019)11:1107–1122 https://doi.org/10.1007/s12520-017-0583-5 ORIGINALPAPER The trade of glass beads in early medieval Illyricum: towards an Islamic monopoly ElisabettaNeri1&BernardGratuze1&NadineSchibille1 Received:23August2017/Accepted:29November2017/Publishedonline:12January2018 #TheAuthor(s)2018.Thisarticleisanopenaccesspublication Abstract ThetradeofglassbeadshaslongbeenassumedtohavebeenunderIslamicdominanceduringtheearlycenturiesfollowingthe Arab conquest of the Middle East, judged by the prevalence of Islamic beads in the archaeological contexts from Viking ScandinaviatomedievalMorocco.ThispaperexplorestheimpactoftheByzantine-Slavictransitionontheuseandbyextension tradeofglassbeadsintheBalkansfromtheseventhtotheninthcenturyCE.Aseriesof48glassbeadsand4vesselfragments fromtwoexcavatedsitesinmoderndayAlbaniahavebeenanalysedmorphologically,technologicallyandchemicallybyLA- ICP-MS.Theseventh-centurybeadsfromLezhahavetypologicalparallelsamongcentralEuropeanassemblagesandaremade fromrecyclednatron-typeglass.Thepresenceofahighlead-iron-natronvariantisofparticularinterestasitpotentiallyreflectsa regional production. The ninth-century beads from Komani are made from soda-rich plant ash glass from the eastern Mediterranean and Mesopotamia and correspond to an Islamic typology. The chronological and geographical differences are reflectedinthedistinctivecobaltsourcesusedforthetwogroups.WhilethebeadsfromLezhaarecolouredwithacobaltnot correlatedwithanyparticularelement,thecobaltsourceoftheKomanisamplesisassociatedwithzinc,typicalofIslamicglass making.ItthusappearsthatthesupplyofbeadsduringtheseventhcenturywhentheBalkanswereunderSlavicoccupationrelied onregionalproductionandrecycledmaterial,andthatalong-distancetradewiththeeasternMediterraneanwasrevivedfollowing theByzantinere-conquestofthesouth-easternAdriaticintheninthcentury.Intriguingly,theAlbanianfindsconfirmtheIslamic controloftheproductionandtradeofglassbeadsduringthisperiodandhighlightthemediatoryroleoftheByzantineEmpire. Keywords Glassbeads .EarlyMiddleAges .Illyricum .Recyclednatronglass .Blackleadglass .Islamicsodaashglass .Cobalt . Nickel .Zinc .Indium .Leadtincalx .Commercialnetwork .Balkans Introduction chemicalsignatureofglassbeadsislinkedtotheirmorpholo- gyandtechnology,whichinturnareconnectedtogeo-cultural The multidisciplinary study ofglassbeadsinearly medieval traditions(PionandGratuze2016).InearlymedievalEurope, contextshasprovedparticularlyfruitfultoelucidatecommer- for example, only wound beads, manufactured by rotating cialandculturalnetworks(Pion2014;PionandGratuze2016; molten glass around a mandrel (metal rod), were produced. Koleini et al. 2016; Wood 2012; Dussubieux et al. 2008; WorkshopsofwoundbeadsaredocumentedinLombardItaly Dussubieux and Soedewo 2016). Ithas been shown that the (e.g. Aiano Torraccia: Cavalieri and Giumlia-Mair 2009), in continental Europe during Merovingian times (e.g. Maastricht, Wijnaldum and Huy: Pion 2014), in Viking Electronicsupplementarymaterial Theonlineversionofthisarticle Scandinavia at Haithabu, Paviken and Ribe (Sode 2004; (https://doi.org/10.1007/s12520-017-0583-5)containssupplementary material,whichisavailabletoauthorizedusers. CallmerandHenderson1991),intheBalkansatPreslav,and in the ninth- to tenth-century Caucasus (Bezborodov 1959). * ElisabettaNeri Drawn beads obtained from segmented tubes, on the other [email protected] hand,aremorecommoninEgypt,intheLevantandinIndia * NadineSchibille (Francis 1990, 2002, 2004).There are two main methods of [email protected] drawn bead production: hot and cold cutting. Workshops of hot-cut beads have been found in Egypt, at Kom-el-Dikka 1 IRAMAT-CEB,UMR5060,CNRS/Universitéd’Orléans,3D,ruede near Alexandria, dating to the fifth and sixth centuries, and laFérollerie,45071Orléanscedex2,France 1108 ArchaeolAnthropolSci(2019)11:1107–1122 atseventh-toeleventh-centuryFustat(Arveiller-Dulong and Egorkov 2006; Jennings 2010; Schibille 2011; Šmit et al. Nenna 2011). No archaeological evidence of workshops for 2012). cold-cut beads have as yet been identified in the eastern Forty-eightbeadsandfourvesselfragmentswereselected Mediterranean. Anthropological studies attribute this tech- from the necropoleis of two late antique foundations on the nique to the Indo-pacific tradition of the ‘lada method’ still riverDrin,thecoastaltownofLezhaandthetownofKomani practisedtoday(Francis1990,Fig.2andpl.III,b;Kanungo locatedfurtherinland(Fig.1).Lezha(Alessio,Lissos,41.78 2004).Accordingtothismanufacturingtechnique,beadsare N, 19.64 E) was a long-lived (sixth to sixteen century CE) producedbydrawingtheglassusingataperedirontubewitha fortifiedsettlementwithaseventh-centurychurchandanas- largeend,theso-calledlada,intoglasscylindersthatarethen sociated cemetery extra muros used from the sixth to the cold-cutintobeads(Francis2002;PionandGratuze2016). twelfthcentury.Komani(Koman,42.08N,19.82E),bycon- ThestudyofMerovingianandLombardbeadsshowedthat trast,wasamuchlargertownwithsixchurchesandanexten- most of the beads produced in central Europe between the sive necropolis. There is evidence of two distinct periods of sixthandeighthcenturywerewoundbeadsmadefromnatron urbandevelopment,thefirstduringthesixthandseventhcen- typeglassderivedfromtheprimarysourcesinEgyptandthe tury, and a second phase in the ninth and tenth century. The Levantorfromrecycledcullet(Mathisetal.2013;Pionand site was finally abandoned in the thirteen century (Nallbani Gratuze2016;Pion2014;Poulainetal.2013;Verità2012).In etal. 2016a).Theeighteenbeads fromLezha were found in addition to these locally produced wound beads, segmented thecontextofdressedinhumations(Fig.2)datedtothesev- drawn beads produced from soda plant ash glass and small enthcenturyCEbasedontheassociatedfinds,andtwomedi- Indo-Pacificbeadsofhighaluminoussodaglassweresimul- evalsamplesfromanIslamicgrave(Table1)(Nallbanietal. taneously imported (Pion and Gratuze 2016). This provides 2016a). The 33 beads from Komani were part of the grave ampleevidenceoflong-distancetradenetworksthatconnect- goodsfromsixdifferenttombs,twoofwhichhavebeendated ed western Europe with the eastern Mediterranean and the by 14C to the ninth or tenth century. The other graves and Indian Ocean during the fifth and early sixth century CE. gravegoodscanbeattributedtothesameperiodbyassocia- Theseeasternimportsceasedsometimeduringthelatersixth tion (Nallbani et al. 2016b). In three cases, entire necklaces century, the reasons for which are still unknown (Pion and werefoundintact(Fig.3).Inaddition,fourfragmentarylitur- Gratuze2016;CalligaroandPérin2013).Followinganinter- gicalglassvesselsfromtheannexofthemainchurchandfrom val of about two centuries, the long-distance trade of glass thesettlementaroundthechurchofSt.Georgewereanalysed beads experienced a revival in the ninth century, after the forcomparativereasons.Whilethebeadswereusedtodem- Abbasidcapitalandpoliticalfocushadshiftedeastwardsfrom onstrate status and prestige and were culturally associated DamascustoBaghdad(Sode2004;Robertshawetal.2010). with Slavic traditions (Wood 2012), the lamps and Thisreorientationarguablyplayedaroleintheconsolidation unguentarium fromthe ecclesiastical contextsare associated of networks of exchange and the influx of Mesopotamian with the Byzantine religious élite (Cheynet 2006). The con- beads to the Mediterranean region and as far as Viking siderationofthevesselfragmentswithinthisstudythusallows Scandinavia(Callmer1977;Steppuhn1997;Steppuhn1998; us to relate the objects types to specific socio-political Sode2004). contexts. This paper presents the first extensive study of medieval glass beads from south-western Illyricum in modern-day Material and methods Albania,combiningtypologicalwithanalyticalmethods.This geographicalregionisimportantbecauseitoccupiesacentral positionandwasacrucialcommercialhubthatconnectedthe Thesamplesanalysedinthisstudywereselectedtocoverthe eastern Mediterranean with western Europe. The glass beads entire range of different typologies, colours and techniques analysedarefromtwowell-datednecropoleisintheDrinval- identified among the assemblages from the two necropoleis ley.ThematerialfromLezhaisattributedtotheseventhcentu- at Lezha and Komani (Table 1). The cleaned but otherwise ry, while the beads from Komani come from ninth- to tenth- unpreparedglassbeadsandfragmentswereanalysedbyLaser centurycontexts.Thisis acriticalperiod inthe historyofthe Ablation Inductively Coupled Plasma Mass Spectrometry Balkans as it encompasses the Slavic invasion in the seventh (LA-ICP-MS). The analyses were conducted at the Centre century and the Byzantine re-conquest in the ninth (Bavant Ernest-Babelon of the IRAMAT (Orléans), using a 2004; Cheynet 2006; Popovic 1980; Lemerle 1980; Fine Thermofisher Element XR combined with a Resonetic UV 1983). The relationship between the vitreous materials and lasermicroprobe(ArF193nm)forthedirectanalysesofsolid bead morphologies of the two sites can thus reveal how the samples (Gratuze 2016; Schibille et al. 2017). Single-point transitionalperiodimpactedthetradeofbeadsandtheorgani- analyses were carried out with a laser beam diameter of sationofsupplymoregenerally(forpreviousstudiesonglass 100μm,operatedat5mJandapulsefrequencyof10Hz.A from the Balkans see, for example, Cholakova et al. 2016; pre-ablation time of 20 s, occasionally increased to 40 s to ArchaeolAnthropolSci(2019)11:1107–1122 1109 Fig.1 MapofAlbaniashowing thelocationofLezha(Lezhë)and KomaniintheDrinValley ensurethe removal ofpossible corrosion layers orothersur- Alamannecropoleis(Koch1977;Giesler-Müller1992).This face contaminations, was followed by 30 s collection time. is in contrast to the assemblages from two Serbian sites of Blanks were run after every ten samples to determine the Viminacium and Singidunum where drawn beads are preva- offset.Theresponsecoefficient(k)foreachelementwascal- lent(Ivaniševićetal.2006). culatedbasedonasetoffiveglassstandards(NISTSRM610, The ninth-and tenth-century beads fromKomaniand the CorningB,C,DandAPL1,anin-housestandard)toconvert twomedievalbeadsfromLezhavarylikewisegreatlyinshape the signals into quantitative data. Corning A and NIST 612 (umbilical,annular,tubular,mosaic,metalsandwich)andcol- glassstandardsweresystematicallymeasuredatregularinter- our(yellow,blue,white),buttheyaremostlydrawnandhot- valstodetermineaccuracyandprecision.Theanalyticalpre- cut,withorwithoutahotfinish(Table1).Similardrawnand cisionreflectedintherelativestandarddeviation(σ)wasgen- hot-cutbeadshavebeenfoundinsixth-andseventh-century erally better than 5% for most elements and accuracy was Serbiancontexts(Ivaniševićetal.2006),amongfifth-tosixth- mostlybetterthan10%(Supplementarymaterial,TableS1). century Merovingian assemblages (Pion 2014), a sixth to seventh-century southern Italian necropolis (Corrado 2012), some ninth- to eleventh-century Viking sites (Sode 2004) as Results well as across the Islamic Mediterranean (Francis 2004). A handful of small beads from a necklace retrieved from a Typologyandgeographicaldistribution tenth-centurytombarecold-cutandapparentlyproducedwith the ‘lada method’ (K_008, K_009, K_010, K_011). Indian Theseventh-century beadsfromLezhaare all woundbeads, cold-cut beads are known to have been imported to western but vary in shape and manufacturing technique, including Europeuptothesixthcentury(PionandGratuze2016).The monochromebeadsofvariousshapes(spherical,annular,spi- beads from Komani suggest that Indian ‘lada beads’ might ral-shaped, bi-conic), monochrome beads with applied fila- have been imported to the Mediterranean region as late as ments, pinched flower-shaped or three-lobed and moulded the tenth century. Several types of wound beads from beads (Table 1). All these types are widely attested in Komani such as the spherical beads with eye decorations Merovingian (Pion 2014), Lombard (Giostra 2012) and (K_033)orpolychromerods(K_029)showsimilaritieswith 1110 ArchaeolAnthropolSci(2019)11:1107–1122 the ninth- and tenth-century samples show a soda-rich plant ashsignature,reflectedinhighpotassium,magnesium(Fig.5) and phosphorus oxide contents. Two opaque yellow beads (Lz_012, K_013,) have unusually high lead contents (PbO 70%) with very low quantities of formers and modifiers. Similar compositions have been observed in some Islamic greenandyellowbeadsatAl-Basra(Robertshawetal.2010) andtheSerçeLimanishipwreck(Brill2009).Inthecaseofthe Albanianbeads,theexceptionallyhighleadcontentcouldbe theresultofpureleadstannate,usedasahalf-productsuchas ‘anima’ known fromVenetian recipes (Morettiand Hreglich 1984). A crucible with comparableresidues of lead stannate for bead-making was retrieved fromthe Merovingian siteof Schleitheim (Heck et al. 2003). However, it cannot be ruled out that the two beads represent highly devitrified lead stannate coloured glass, but the low phosphorus contents makethislesslikely. Natronglassbeads The majority of the seventh-century wound glass beads, as well as three ninth- to tenth-century colourless beads (n= 12)haveanatron-typebaseglasswithelevatedlevelsofmag- nesium, titaniumand iron,associatedwithslightly increased vanadium, chromium and zirconium. These characteristics correspondtothe so-called Foy-2 compositional group (Foy Fig. 2 Seventh-century dressed inhumation (tomb T157) at Lezha (Nalbanietal.2016,photo:DidierDubois) et al. 2003). Foy-2 glass appears to have been a relatively widespread glass type during the sixth and seventh century the wound Islamic beads excavated at different Viking sites and is believed to be of an Egyptian provenance (Nenna (Sode 2004; Callmer and Henderson 1991; Steppuhn 2014; Ceglia et al. 2015; Cholakova et al. 2016; Neri et al. 1997; Steppuhn 1998). The colourless ovoidal flat bead 2017;Schibilleetal.2017). (K_027)andthecolourlessbeadsdecoratedwithawhiteoc- Therearefouroutliersintermsoftheelementsassociated ulus (K_006, K_026) usually occupy the most prominent withthesilicasources(Fig.6).Thewhiteglassofthespherical placewithinthenecklace(Fig.3). wound bead (K_026) has high calcium and low aluminium Theglassfragmentsincludedinthisstudycanbeattributed oxidecontents,highchromium,magnesium,titaniumandlow toecclesiasticallamps,datedtypologicallytothefifthtoelev- strontium levels. This profile is typical of so-called Egypt II enth century (Fig. 4a–c) (Antonaras 2008). While they are glassthatwasfirstidentifiedamongeighth-andninth-century relatively common elsewhere, for instance in Thessaloniki, Islamic glass weights from Egypt (Gratuze and Barrandon this is the first time they have been identified in Albania 1990). One colourless wound bead (Lz_017) has a (Antonaras 2008, Jennings 2010). Finally, the last fragment Levantine composition, exceptfor its lower alumina content with a marvered decoration belongs to a spindle-shaped (1.25%). The flower-shaped wound bead (Lz_004) with unguentarium, usually dated to between the tenth and four- equally low alumina (1.5%) and high antimony oxide teenthcentury(Fig.4d)andislinkedtoanAbbasid produc- (2.5%)concentrationsbearssimilaritieswithRomanantimo- tion. A similar object was found in Montenegro (Antonaras nydecolouredglass,butforitsrelativelyhighlimeconcentra- 2010a). tion (Jackson 2005). The somewhat unusual trace element patterns,includinglowtitaniumbuthighzirconium,relatively lowstrontiumandelevatedcopperlevelssuggestsomedegree Chemicalsignatureofthebeads of recycling and mixing of Roman antimony glass with an- other glass type. The polygonal transparent blue bead TheLA-ICP-MSanalysisofthebeads(Table2)clearlyiden- (Lz_016)hashighantimonyoxide(2%)levels,possiblyasa tifiestwodistinctgroupsaccordingtothealkalinesourcethat resultofrecycledblueRomanmosaictesseraeopacifiedwith correspond to the chronology of the beads. Whereas all the antimony.Someofthecompositionalvariationsareprobably seventh-centurybeadsarenatron-typeglasses,themajorityof due to the recycling and mixing of new base glass with ArchaeolAnthropolSci(2019)11:1107–1122 1111 Table1 GlassbeadsfromLezhaandKomani Photograph Base glass Sample (scale bar: 1 cm) Archaeological context Typology Date Colorants & opacifiers Natron, Foy 2.1 Lezha Lz_001 Wound with filaments 7thc. Red: Cu tomb 157 White: SnO Mesopotamian Lezha Drawn, incised and hot Lz_002 13thc. plant ash tomb 34 finished Blue: Co-Zn Lezha Natron, Foy 2.1 Lz_003 Wound,monochrome 7thc. tomb 157 Blue: Co-Ni Lezha Wound, incised flower- Lz_004 7thc. Natron, Foy 4 tomb 146 shaped Lezha Wound, monochrome, Lead iron manganese natron Lz_007 7thc. tomb 157 annular Black: Fe-Mn Lezha Natron, Foy 2.1 Lz_008 Wound, bi-conic 7thc. tomb 146 White: SnO Lezha Wound, monochrome, High lead iron manganese natron Lz_009 7thc. tomb 146 ovoidal Black: Pb-Fe Lezha Wound, deformed by Natron, Foy 2.1 Lz_010 7thc. tomb 157 gravity Blue: Co-Ni Natron, Foy 2.1 Lezha Wound, deformed by Lz_011 7thc. Blue: Co-Ni tomb 157 gravity Lezha Wound, monochrome, Devitrified Lz_012 7thc. tomb 157 circular Yellow: SnPb Lezha Wound, monochrome, High lead iron manganese natron Lz_013 7thc. tomb 157 annular Black: Fe-Mn Lezha Natron, Foy 2.1 Lz_014 Wound, bi-conic 7thc. tomb 157 White: SnO Lezha Natron, Foy 2.1 Lz_015 Wound annular 7thc. tomb 157 Blue: Co-Ni Lezha Wound, moulded Natron, Foy 2.1+Foy4 Lz_016 7thc. tomb 50 polygonal monochrome Blue: Co 1112 ArchaeolAnthropolSci(2019)11:1107–1122 Table1 (continue) Lezha Wound, ovoidal, Lz_017 7thc. Natron, Foy low in alumina (Levantine) tomb 50 monochrome Lezha, Wound, ovoidal, High lead iron manganese natron Lz_018 7thc. tomb 50 monochrome Brown: Pb-Fe Mesopotamian Lezha Drawn, monochrome, Lz_019 13thc. plant ash tomb 34 hot-finished Green: Cu, SnPb Lezha Wound, monochrome, Natron, Foy 2.1 Lz_020 7thc. tomb 157 spiral-shaped Yellow: SnPb Lezha Wound, monochrome, High lead iron manganese natron Lz_021 7thc. tomb 157 three-lobed Black: Pb-Fe-Mn Lezha Wound, with filaments Natron, Foy 2.1 Lz_022 7thc. tomb 157 applied (body) Yellow: Sn(Sb)Pb Mesopotamian plant ash White: Sn+Pb Komani Drawn, mosaic with eye K_001 9th-10thc. Yellow: SnPb (As, Sb) tomb 321 decoration Blue: Co-Zn Green: Cu/ SnPb Red:Cu Mesopotamian Komani Wound, with eye plant ash K_002 9th-10thc. tomb 321 decoration Blue: Co-Zn White: SnO Mesopotamian Komani Wound, deformed by K_003 9th-10thc. plant ash tomb 321 gravity and pressed Blue: Co-Zn Komani Drawn, monochrome, Mesopotamian plant ash K_004 9th-10thc. tomb 321 annular Yellow: SnPb Mesopotamian Komani Drawn, monochrome, K_005 9th-10thc. plant ash tomb 321 annular Blue: Co-Zn Komani Wound, circular with Natron, Foy 2 K_006 9th-10thc. tomb 321 oculus (body) White: SnO ArchaeolAnthropolSci(2019)11:1107–1122 1113 Table1 (continue) Mesopotamian Komani Drawn, monochrome, K_007 9th-10thc. plant ash tomb 321 annular White: SnO Komani Drawn, cold-cut, Levantine plant ash K_008 9th-10thc. tomb 319 monochrome, annular Green: Cu/Fe/SnPb Drawn, cold-cut, hot- Komani Levantine plant ash K_009 finished, monochrome, 9th-10thc. tomb 319 Green: Fe/Cu annular Drawn, cold-cut, hot- Komani Levantine plant ash K_010 finished, monochrome, 9th-10thc. tomb319 Green: Cu/Fe annular Drawn, cold-cut, hot- Komani Levantine plant ash K_011 finished, monochrome, 9th-10thc. tomb 319 Purple: Fe/Mn annular Mesopotamian Komani Drawn, monochrome, K_012 9th-10thc. plant ash tomb 319 annular White: SnO Komani Drawn, monochrome, devitrified K_013 9th-10thc. tomb 321 annular Yellow: PbSn (As, Sb) Mesopotamian Komani Drawn, monochrome, K_014 9th-10thc. plant ash tomb 319 annular Blue: Co-Zn Mesopotamian plant ash Komani Drawn, mosaic with eye White: SnO K_015 9th-10thc. tomb 319 decoration Yellow: SnPb (As, Sb) Blue: Co-Zn Red: Cu Mesopotamian Komani Drawn, monochrome, K_016 9th-10thc. plant ash tomb 319 spherical Blue: Co-Zn Mesopotamian Komani Drawn, segmented, K_017 9th-10thc. plant ash tomb 375 spherical, monochrome Yellow: SnPb (As, Sb) Drawn, segmented, Mesopotamian Komani K_018 metal sandwich, 9th-10thc. plant ash tomb 375 monolobed Silver metal leaf Drawn, segmented, Mesopotamian Komani K_019 metal sandwich, 9th-10thc. plant ash tomb 375 monolobed Silver metal leaf Mesopotamian Komani Drawn, segmented, K_020 9th-10thc. plant ash tomb 375 metal sandwich, bilobed Silver metal leaf 1114 ArchaeolAnthropolSci(2019)11:1107–1122 Table1 (continue) Mesopotamian Komani Drawn, segmented, K_021 9th-10thc. plant ash tomb 375 metal sandwich, bilobed Silver metal leaf Mesopotamian Komani Drawn, monochrome, K_022 9th-10thc. plant ash St. George, US1011 annular Yellow: SnPb Mesopotamian plant ash Komani Drawn, mosaic with White: SnO K_023 9th-10thc. St. George, US1011 eye decoration Yellow: SnPb Green blue: Cu Red: Cu Mesopotamian plant ash White: SnO Komani Drawn, mosaic with eye K_024 9th-10thc. Yellow: SnPb St. George, US1011 decoration Green blue: Cu Red: Cu Blue: Co-Zn Natron, Foy2.1 Komani Wound, spherical with K_026 9th-10thc. Natron, Egypt II Tomb 340 oculus (body) White: SnO Komani Wound, pressed, K_027 9th-10thc. Natron, Foy 2.1 Tomb 340 ovoidal, monochrome Drawn, segmented, hot- Mesopotamian Komani K_028 finished, metal 9th-10thc. plant ash Tomb 340 sandwich (ext.) Silver metal leaf Mesopotamian plant ash Body: Cu+SnPb Komani Wound, covered with White: SnO K_029 9th-10thc. Tomb 340 polychrome rods (ext.) Red: Cu Green: Cu Yellow: SnPb Blue: Co-Zn Mesopotamian Komani Wound, with eye plant ash K_033 9th-10thc. tomb 340 decoration Blue: Co-Zn White: SnO Mesopotamian Komani Drawn, segmented, K_034 9th-10thc. plant ash tomb 340 monochrome, polylobed Blue: Co-Zn ArchaeolAnthropolSci(2019)11:1107–1122 1115 ratio (4:1) that is congruous with a cobalt source associated withelevatednickelthatappearstohavebeenexploitedsince thesixthcentury(Schibilleetal.2017). The black glass beads fromLezha(n=5)havea peculiar composition with high lead (PbO 28–34%) and iron (FeO 7.7–15.2%) contents, similar to some sixth- to seventh- century Merovingian beads (Poulain et al. 2013; Mathis et al. 2013; Pion and Gratuze 2016). They are probably the result of a mixture of recycled natron glass witha high lead andironcomponent,introducedintheformofleadandiron oxides or metallurgical scrap (Mecking 2013; Gratuze et al. 2003).Thetrilobedbead(Lz_021)appearstobesomewhatof anoutlier,differingnotonlyinshapebutalsoincomposition Fig.3 Necklacefromaninth-ortenth-centurytomb(T319)inKomani from the other black beads. It has significantly lower soda (photo:DidierDubois) contents,whilemanganeseandaluminiumarenotablyhigher. These features suggest that this bead is the product of a dif- tesseraeandculletofvariousorigins.Inparticular,thetraces ferentsecondaryworkshop. ofcobalt(CoO0.01–0.03%)andcopper(CuO0.15–0.5%)in colourless oryellowbeads and elevatedphosphorusand po- Sodaashglass tassium contents (e.g. K_026) can indicate the recycling of colouredcullet(Table2). Theninth-totenth-centurydrawnandwoundbeadsaremade Judging from the compositional analysis, the colourants fromsodaplantashglass,characterisedbyhigherpotashand and opacifying agents used include tin oxide to obtain the magnesiacontents(>2%)associatedwiththeplantashcom- whitebeadsandleadstannatetoobtainyellow,botharetyp- ponent. Two sub-groups can be distinguished on account of icaloftheearlymedievalperiodafterthefourthcentury,when their varying lanthanum, chromium, titanium and zirconium tin increasingly replaced antimony as opacifier (Tite et al. contents that reflect different silica sources (Fig. 7a, b). The 2008). The blue beads are coloured with cobalt (500– differentsilicagroupsalsoexhibitdifferencesinrelationtothe 900 ppm). The cobalt used for the natron-type beads is not alkalicontentswithdistinctmagnesiumandphosphorusratios unambiguously associated with any particular impurities, (Fig.7c).Thelargestgroupcomprisingallbutfourplantash which is a trademark of Roman cobalt sources (Gratuze beads fromKomaniand Lezha (n=24),has veryhighmag- etal. 1992).One sample(K_026) has a lowcobaltto nickel nesium contents (MgO>3.5%), relatively low phosphorus levelsandamuchlowerpotassiumtomagnesiumratiocom- paredtothefourbeadsfromKomanithatclearlyformasep- arategroup(Table2,Fig.7).Thesecharacteristicsaretypical ofplantashglassesfromSasanianandAbbasidMesopotamia (Mirti et al. 2009; Pion and Gratuze 2016; Henderson et al. 2016),anattributionthatisconfirmedbytheirlowlanthanum andelevatedchromiumcontents(Shortlandetal.2007).The fourseparatebeadshaveonaveragehighertitaniumtozirco- niumratios,clearlypointingtodifferencesinthesilicasource and by extension different origins (Fig. 7a, b). Intriguingly, thesefoursmallbeads(K_008,K_009,K_010,K_011)have been manufactured by cold-cutting in imitation of the Indo- Pacific‘lada’technique.Hence,theyformtypologicallyand compositionally a very tight group, suggesting a common provenance.Nocompositionalparallelsamongpublisheddata ofNearEasternorMesopotamianplant-ashglasseshavebeen identified, neither for the silica source (higher alumina con- tents) nor for the alkali sources (lower calcium and higher potassium oxides levels) (Henderson et al. 2004, 2016; Fig.4 GlassartefactsfromKomani.aSnaketrailedlamp(similartotype Henderson and Allan 1990; Gratuze and Barrandon 1990; 3.ii in Antonaras 2008). b Lamp with handle (similar to type 4 in Antonaras2008).cLampwithhandle(similartotypeII.iinAntonaras Katoetal.2010).Apossibleexceptionaresomesamplesfrom 2008).dSpindle-shapedunguentarium Raqqa group 4 that are high in alumina and magnesia 1116 ArchaeolAnthropolSci(2019)11:1107–1122 Table2 LA-ICP-MSdataoftheLezhaandKomanisamples.Majorandminoroxides[wt%],includingchlorine,andtraceelements[ppm];n.i.not identified (Henderson2003a).Ithasbeenarguedthatthesemightbethe zinc-rich cobalt is generally associated with Islamic glass resultofexperimentation(Hendersonetal.2004). making (Gratuze et al. 1992; Henderson 2003b; Wood Someofthecolourantsrepresentedamongtheplant-ash 2012)andhasbeenidentifiedamongtheearlyIslamicglass glass beads similarly confirm the chronological and geo- from Tyre (Freestone 2002) and the al-Barsa beads graphical attribution of the groups. The cobalt in the blue (Robertshaw et al.2010). The yellow and greenish yellow beadsisstronglycorrelatedwithzinc(Fig.8).Thistypeof samples contain lead stannate pigments that occasionally
Description:The list of books you might like
