Glass beads from Kissi (Burkina Faso): chemical analysis and archaeological interpretation

97

Glass Beads from Kissi (Burkina Faso)

Glass Beads From Kissi (Burkina Faso): Chemical Analysis and Archaeological Interpretation

Peter Robertshaw, Sonja Magnavita, Marilee Wood, Erik Melchiorre, Rachel Popelka-Filcoff & Michael D. Glascock

AbstractChemical analysis, using LA-ICP-MS, of 37 glass beads from the cemetery of Kissi 13 in Burkina Faso revealed the presence of three main types of glass. Soda-lime-silica glass, manufactured using plant ash as the flux, was the glass type from which almost all the beads were made. Western Asia, specifically the region east of the Euphrates River, was the probable source of most of this glass, except for four beads made from glass likely manufactured in the Levant. One bead is made of a high-alumina, high-lime glass manufactured in West Africa. Another has white stripes from the probable use of the mineral pyromorphite as a coloring agent. Although chemical analysis aids in the identification of the sources of the glass, the analysis does not shed light on where the beads themselves were made.

RésuméL'analyse chimique, utilisant LA-ICP-MS, de 37 perles de verre du cimetière de Kissi 13 au Burkina Faso ont révélé la présence de trois types principaux de verre. Le verre silico-sodo-calcique, fabriqué utilisant la cendre de plante comme le flux, constitue la matière première de presque toutes les perles. L'Asie de l'Ouest, en particulier la région à l'est du fleuve Euphrate, était la source probable de la plus grande partie de ce verre. Seules quatre perles ont été réalisées avec un type de verre comparable mais probablement fabriqué dans le Levant. Une autre perle est faite d'un verre à forte concentration d’aluminium et de cal-caire, fabriqué en Afrique d'Ouest. Un autre présente des raies blanches dues à l’utilisation probable de la pyromorphite comme colorant. Bien que l'analyse chimique aide à l'identification des sources du verre, l'analyse ne permet pas de mettre en lumière la localisation géographique des ateliers de fabrication de perles.

IntroductIon

Archaeological research by a team of the Frankfurt Joint Research Project discovered and subsequently excavated a cluster of settlements and cemeteries near the Mare de Kissi in northeast Burkina Faso that span the period from the 4th century BC to the 12th or 13th century AD (MagnavIta et al. 2002). Numerous beads made from a wide variety of raw materials were re-covered during excavations. While glass beads were rarely found on the settlements, more than 1000 glass beads, out of a total of about 5000 beads, were found in the cemeteries (MagnavIta 2003). A preliminary description of the glass beads has been published previ-ously, together with the results of chemical analysis of seven glass beads from the cemetery of Kissi 3, which dates to the 5th–7th centuries AD (MagnavIta 2003). These first chemical results were recently rejected by the analyst, G. Brey, because of a program error that occurred during the analyses. A detailed study of the beads recovered at Kissi is presented in MagnavIta (2006), including further chemical analyses of glass beads done by R. Brill from Corning Museum of Glass (see also MagnavIta, this volume). In this paper we present the results of chemical analysis, using laser-ablation inductively-coupled mass spectrometry (LA-ICP-MS) at the University of Missouri Research Re-actor Center (MURR), of 37 glass beads, all of which

were discovered in the cemetery of Kissi 13 at depths of 100–120 cm. While this cemetery was in use in the ca 4th–11th centuries AD, the analyzed beads were chosen from an horizon with disturbed graves believed to date towards the end of the first millennium AD; two AMS radiocarbon dates from 100 cm and 110 cm below surface yielded calibrated ages (at two sigma) of 770–1020 AD and 670–970 AD respectively, while a grave about 90 cm below this level was dated to 330–610 AD. Beads presumed to date towards the end of the first millennium were targeted for analysis to provide comparative data for a larger chemical study of beads from the famous contemporary site of Igbo-Ukwu in Nigeria (Shaw 1970). We present the results of our chemical analyses of the beads from Kissi 13 and attempt to identify the likely source areas of the glass used to make the beads.

The analyzed beads (Fig. 1) have varied shapes (tubular, cylindrical, oblate, and barrel-shaped) and are manufactured from drawn tubes of glass, some of which have ends that have been reheated and/or ground flat. The beads vary in color, but all except three are monochromatic. The three exceptions are PR680 and 681, both of which have vertical white stripes on a purple-colored base, and PR716, a turquoise-colored bead with a blob of yellow. For this last bead, only the turquoise portion was analyzed.

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analytIcal Method

The bead samples were analyzed at MURR by Glascock and Popelka-Filcoff who used a high-resolution Axiom ICP-MS with a New Wave 213 nanometer laser-ablation system for the sample introduction system. As described in greater detail elsewhere (robertShaw et al. 2006; SpeakMan & neff 2005), each sample was measured for elemental concentrations using a continuous line scan of approximately 2 millimeters length to provide the most accurate bulk characterization. To eliminate the effects of surface contamination, each line was pre-ablated twice before the start of data collection.

The analytical menu consists of 47 elements rang-ing from lithium to uranium measured sequentially. Calibration lines for each element are established by analyzing SRM612 and SRM610 glass standards from the National Institute of Standards and Technology along with the Brill glasses (brIll 1999: II, 527–544) and obsidian glass from the Pachuca and Glass Buttes sources (glaScock 1999). Beads and standards are acquired by three or five runs through the analytical menu followed by blank runs to avoid memory effect. This method allows for averaging the results to account for variation occurring within the system during the run as well as between runs throughout the day.

Elemental concentrations for the beads were cal-culated using a normalization procedure described by gratuze et al. (2001) that sums the total concentration

of oxides to 100 %. Precisions reported as relative standard deviation for the elements range from 2 to 20 % depending upon the strength of the signal for each element. A comparison of the accuracy between our results for the calibration standards and published values for the standards is in the range of 5 to 10 % for most of the elements.

reSultS

The results of the analyses are presented in Table 1, where the beads are grouped according to their glass types (see below). Beads with their color information are presented along the rows, and calculated oxides of the elements of interest are presented along the columns following the order of the periodic table. Values not listed with a percentage (%) are presented as parts per million (ppm). Oxides containing less than 1000 ppm (0.1 %) are shown as ppm; higher amounts are shown as a percent-age. Major oxides in most glasses comprise Na2O, MgO, SiO2, Al2O3, K2O, and CaO, whereas other oxides are usually minor and trace compositions of the glass.

A common first step in the examination of glass compositional data is to calculate the reduced compo-sitions of the glass beads by normalizing seven major and minor oxides to 100 %. This normative reporting removes most of the compositional effects of addi-tives, such as most colorants, so that one can examine the main components of the glasses (brIll 1999: II, 8–11). The reduced compositions of the Kissi glass beads are presented in Table 2, where the oxides are marked with an asterisk to indicate that these represent reduced compositions.

There are three major types of glass represented in the results of the analyses. All except one of the beads were made from soda-lime-silica glass in which the source of the alkali used as a flux in the glass manu-facture was a plant ash derived from the burning of alkali-tolerant, halophytic plants growing in coastal, salt marsh or desert regions (barkoudah & henderSon 2006; tIte et al. 2006: 1285). Using the notation sys-tem for glass types devised by lankton & duSSubIeux (2006; see also duSSubIeux 2001), this is vNC glass (Tab. 3), where the initial v (“vegetal”) refers to the source of the alkali (plant ash in this case) and the N and C refer to the glass having relatively high con-centrations of soda and lime (calcia). This plant-ash soda-lime-silica glass has often been referred to in the literature as HMHK (high magnesia, high potash) or as HMG (high magnesia) glass (Sayre & SMIth 1961; henderSon 1985). The sole exception to the presence of vNC glass in our Kissi samples is PR715, which

Fig. 1. The analyzed glass beads from Kissi (not illustrated: PR698, 704, 705 and 711).

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Abb. 48. Die chemisch analysierten Perlen. 9000-9019: Analysen durch R.H. Brill; PR681-716:Analysen durch P. Robertshaw (PR698, 704, 705 und 711: o. Abb.).

1cm

PR... 681 686 682 683 684 685

PR...687 688 689 690 691 692 693 694

PR... 695 696 697 699

PR... 700 701 702 703 706 707 708

PR... 709 710 712 713 714 715 716

9000 (Ki13/-70)

9001 (Ki14/-60)

9004 (Ki13/-170)

9005 (Ki13/-90)

9002 (Ki13/-100)

9003 (Ki13/-10)

9006 (Ki13/-90)

9007 (Ki13/-120)

9008 (Ki14/-60)

9009 (Ki14/-40)

9010 (Ki14/-60)

9011 (Ki14/-0)

9012 (Ki3/-250-260)

9015 (Ki13/-40)

9013 (Ki13/-110)

9014 (Ki13/ -110)

9016 (Ki13/-10)

9017 (Ki14/-70)

9018 (Ki14/-60)

9019 (Ki14C,Grab2, Nr. H60)

Anhang C

I

PR680 PR680-W PR681 PR681-W PR682 PR683 PR684 PR685 PR686

violett weiss violett weiss hellgrün türkis türkis blau blau

Li2O 51.2 47.1 44.2 0.6 70.3 34.4 44.6 52.7 55.4

Na2O 13.04% 13.88% 10.35% 0.21% 12.17% 7.80% 10.68% 11.17% 12.83%MgO 4.05% 4.87% 3.41% 1.24% 2.00% 2.60% 4.01% 3.26% 4.38%Al2O3 2.93% 1.09% 3.14% 2.20% 2.22% 2.75% 2.36% 2.89% 4.04%SiO2 67.10% 56.27% 70.32% 29.80% 68.25% 74.10% 70.06% 68.46% 64.52%

P2O5 0.26% 0.47% 0.25% 13.63% 0.54% 0.34% 0.24% 0.30% 0.37%

K2O 2.76% 2.70% 2.81% 0.28% 2.79% 2.58% 2.92% 2.55% 3.46%CaO 6.80% 4.86% 7.06% 14.27% 9.39% 6.81% 7.36% 9.42% 7.02%TiO2 0.12% 531.8 0.14% 636.7 0.13% 0.17% 0.14% 0.15% 0.15%

V2O5 31.8 16.7 32.1 258.7 22.5 31.8 27.4 27.2 30.6Cr2O3 71.4 15.6 74.1 30.2 13.5 78.4 73.7 42.9 75.6

MnO 1.68% 345.6 1.76% 248.8 1.09% 577.9 382.2 0.30% 1.34%Fe2O3 0.57% 0.37% 0.56% 0.44% 0.88% 0.72% 0.55% 0.78% 1.24%

CoO 571.7 2.0 13.4 3.9 28.7 7.8 2.8 485.9 959.2NiO 10.3 7.4 32.2 12.8 22.8 87.8 83.7 150.5 225.6

CuO 359.2 127.7 79.3 206.0 100.8 1.77% 1.42% 0.16% 0.11%

ZnO 102.3 66.5 39.4 595.4 56.4 188.7 33.0 57.4 145.1As2O3 6.9 315.2 3.2 236.1 8.9 40.9 32.9 38.1 17.8Rb2O 20.0 17.6 22.9 3.0 10.8 30.9 14.4 14.9 25.7

SrO 500.5 470.5 437.2 662.5 333.3 485.5 519.9 672.6 526.6Y2O3 4.8 3.2 6.6 9.8 6.5 5.6 5.8 6.9 6.3ZrO2 116.4 17.1 135.9 23.1 202.6 167.0 208.3 133.5 166.2

NbO2 2.9 1.2 3.1 1.6 3.1 3.6 2.8 2.7 3.4MoO2 4.2 0.5 2.3 0.2 3.6 0.6 0.8 4.0 2.9

InO 13.8 234.3 0.1 337.3 0.2 1.6 1.0 0.7 1.6Sb2O5 7.4 10.9 1.7 11.3 4.8 32.4 61.2 0.17% 10.0SnO2 0.24% 4.50% 21.7 6.57% 57.7 279.9 255.6 77.3 227.5Cs2O 0.3 0.2 0.2 0.0 0.6 0.5 0.2 0.2 0.2BaO 331.1 75.6 247.3 828.0 831.5 142.0 115.6 213.3 407.4

La2O3 5.7 3.1 6.2 9.6 7.0 10.7 7.5 8.6 7.3Ce2O3 10.6 5.7 11.0 10.7 12.6 13.8 14.5 14.6 13.1Pr2O3 1.6 0.9 1.3 1.7 1.4 1.6 1.6 1.9 1.6Nd2O3 6.5 3.1 5.3 7.0 6.5 9.1 6.3 8.1 7.9Sm2O3 1.1 0.5 0.6 1.2 1.0 1.3 1.0 1.8 1.6Eu2O3 0.9 0.0 1.1 0.3 0.8 0.9 1.0 0.7 0.8Gd2O3 1.8 0.5 1.4 1.1 1.5 2.3 1.9 1.3 1.7Tb2O3 0.1 0.1 0.1 0.2 0.1 0.1 0.1 0.2 0.2Dy2O3 1.0 0.4 0.7 0.9 0.9 1.0 0.9 1.2 1.1Ho2O3 0.2 0.1 0.1 0.2 0.2 0.2 0.2 0.2 0.2Er2O3 0.5 0.2 0.5 0.6 0.6 0.5 0.5 0.9 0.7

Tm2O3 0.1 0.0 0.0 0.1 0.1 0.1 0.1 0.1 0.1Yb2O3 0.5 0.3 0.5 0.6 0.6 0.5 0.8 0.8 0.7Lu2O3 0.1 0.0 0.1 0.1 0.1 0.0 0.1 0.1 0.1HfO2 2.1 0.4 2.2 0.4 4.3 2.2 2.7 2.9 3.0

PbO 0.23% 10.75% 822.1 30.95% 0.36% 0.13% 691.2 0.19% 0.24%

ThO2 1.5 0.6 1.4 0.8 2.7 2.1 2.1 1.8 2.2U3O8 0.8 0.3 0.6 1.5 1.1 0.6 0.8 1.1 0.9

Analysenresultate Glas

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1cm

PR... 681 686 682 683 684 685

PR...687 688 689 690 691 692 693 694

PR... 695 696 697 699

PR... 700 701 702 703 706 707 708

PR... 709 710 712 713 714 715 716

9000 (Ki13/-70)

9001 (Ki14/-60)

9004 (Ki13/-170)

9005 (Ki13/-90)

9002 (Ki13/-100)

9003 (Ki13/-10)

9006 (Ki13/-90)

9007 (Ki13/-120)

9008 (Ki14/-60)

9009 (Ki14/-40)

9010 (Ki14/-60)

9011 (Ki14/-0)

9012 (Ki3/-250-260)

9015 (Ki13/-40)

9013 (Ki13/-110)

9014 (Ki13/ -110)

9016 (Ki13/-10)

9017 (Ki14/-70)

9018 (Ki14/-60)

9019 (Ki14C,Grab2, Nr. H60)

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70


1cm

PR... 681 686 682 683 684 685

PR...687 688 689 690 691 692 693 694

PR... 695 696 697 699

PR... 700 701 702 703 706 707 708

PR... 709 710 712 713 714 715 716

9000 (Ki13/-70)

9001 (Ki14/-60)

9004 (Ki13/-170)

9005 (Ki13/-90)

9002 (Ki13/-100)

9003 (Ki13/-10)

9006 (Ki13/-90)

9007 (Ki13/-120)

9008 (Ki14/-60)

9009 (Ki14/-40)

9010 (Ki14/-60)

9011 (Ki14/-0)

9012 (Ki3/-250-260)

9015 (Ki13/-40)

9013 (Ki13/-110)

9014 (Ki13/ -110)

9016 (Ki13/-10)

9017 (Ki14/-70)

9018 (Ki14/-60)

9019 (Ki14C,Grab2, Nr. H60)

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1cm

PR... 681 686 682 683 684 685

PR...687 688 689 690 691 692 693 694

PR... 695 696 697 699

PR... 700 701 702 703 706 707 708

PR... 709 710 712 713 714 715 716

9000 (Ki13/-70)

9001 (Ki14/-60)

9004 (Ki13/-170)

9005 (Ki13/-90)

9002 (Ki13/-100)

9003 (Ki13/-10)

9006 (Ki13/-90)

9007 (Ki13/-120)

9008 (Ki14/-60)

9009 (Ki14/-40)

9010 (Ki14/-60)

9011 (Ki14/-0)

9012 (Ki3/-250-260)

9015 (Ki13/-40)

9013 (Ki13/-110)

9014 (Ki13/ -110)

9016 (Ki13/-10)

9017 (Ki14/-70)

9018 (Ki14/-60)

9019 (Ki14C,Grab2, Nr. H60)

680

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1cm

PR... 681 686 682 683 684 685

PR...687 688 689 690 691 692 693 694

PR... 695 696 697 699

PR... 700 701 702 703 706 707 708

PR... 709 710 712 713 714 715 716

9000 (Ki13/-70)

9001 (Ki14/-60)

9004 (Ki13/-170)

9005 (Ki13/-90)

9002 (Ki13/-100)

9003 (Ki13/-10)

9006 (Ki13/-90)

9007 (Ki13/-120)

9008 (Ki14/-60)

9009 (Ki14/-40)

9010 (Ki14/-60)

9011 (Ki14/-0)

9012 (Ki3/-250-260)

9015 (Ki13/-40)

9013 (Ki13/-110)

9014 (Ki13/ -110)

9016 (Ki13/-10)

9017 (Ki14/-70)

9018 (Ki14/-60)

9019 (Ki14C,Grab2, Nr. H60)

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1cm

PR... 681 686 682 683 684 685

PR...687 688 689 690 691 692 693 694

PR... 695 696 697 699

PR... 700 701 702 703 706 707 708

PR... 709 710 712 713 714 715 716

9000 (Ki13/-70)

9001 (Ki14/-60)

9004 (Ki13/-170)

9005 (Ki13/-90)

9002 (Ki13/-100)

9003 (Ki13/-10)

9006 (Ki13/-90)

9007 (Ki13/-120)

9008 (Ki14/-60)

9009 (Ki14/-40)

9010 (Ki14/-60)

9011 (Ki14/-0)

9012 (Ki3/-250-260)

9015 (Ki13/-40)

9013 (Ki13/-110)

9014 (Ki13/ -110)

9016 (Ki13/-10)

9017 (Ki14/-70)

9018 (Ki14/-60)

9019 (Ki14C,Grab2, Nr. H60)

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1cm

PR... 681 686 682 683 684 685

PR...687 688 689 690 691 692 693 694

PR... 695 696 697 699

PR... 700 701 702 703 706 707 708

PR... 709 710 712 713 714 715 716

9000 (Ki13/-70)

9001 (Ki14/-60)

9004 (Ki13/-170)

9005 (Ki13/-90)

9002 (Ki13/-100)

9003 (Ki13/-10)

9006 (Ki13/-90)

9007 (Ki13/-120)

9008 (Ki14/-60)

9009 (Ki14/-40)

9010 (Ki14/-60)

9011 (Ki14/-0)

9012 (Ki3/-250-260)

9015 (Ki13/-40)

9013 (Ki13/-110)

9014 (Ki13/ -110)

9016 (Ki13/-10)

9017 (Ki14/-70)

9018 (Ki14/-60)

9019 (Ki14C,Grab2, Nr. H60)

I

PR680 PR680-W PR681 PR681-W PR682 PR683 PR684 PR685 PR686

violett weiss violett weiss hellgrün türkis türkis blau blau

Li2O 51.2 47.1 44.2 0.6 70.3 34.4 44.6 52.7 55.4

Na2O 13.04% 13.88% 10.35% 0.21% 12.17% 7.80% 10.68% 11.17% 12.83%MgO 4.05% 4.87% 3.41% 1.24% 2.00% 2.60% 4.01% 3.26% 4.38%Al2O3 2.93% 1.09% 3.14% 2.20% 2.22% 2.75% 2.36% 2.89% 4.04%SiO2 67.10% 56.27% 70.32% 29.80% 68.25% 74.10% 70.06% 68.46% 64.52%

P2O5 0.26% 0.47% 0.25% 13.63% 0.54% 0.34% 0.24% 0.30% 0.37%

K2O 2.76% 2.70% 2.81% 0.28% 2.79% 2.58% 2.92% 2.55% 3.46%CaO 6.80% 4.86% 7.06% 14.27% 9.39% 6.81% 7.36% 9.42% 7.02%TiO2 0.12% 531.8 0.14% 636.7 0.13% 0.17% 0.14% 0.15% 0.15%

V2O5 31.8 16.7 32.1 258.7 22.5 31.8 27.4 27.2 30.6Cr2O3 71.4 15.6 74.1 30.2 13.5 78.4 73.7 42.9 75.6

MnO 1.68% 345.6 1.76% 248.8 1.09% 577.9 382.2 0.30% 1.34%Fe2O3 0.57% 0.37% 0.56% 0.44% 0.88% 0.72% 0.55% 0.78% 1.24%

CoO 571.7 2.0 13.4 3.9 28.7 7.8 2.8 485.9 959.2NiO 10.3 7.4 32.2 12.8 22.8 87.8 83.7 150.5 225.6

CuO 359.2 127.7 79.3 206.0 100.8 1.77% 1.42% 0.16% 0.11%

ZnO 102.3 66.5 39.4 595.4 56.4 188.7 33.0 57.4 145.1As2O3 6.9 315.2 3.2 236.1 8.9 40.9 32.9 38.1 17.8Rb2O 20.0 17.6 22.9 3.0 10.8 30.9 14.4 14.9 25.7

SrO 500.5 470.5 437.2 662.5 333.3 485.5 519.9 672.6 526.6Y2O3 4.8 3.2 6.6 9.8 6.5 5.6 5.8 6.9 6.3ZrO2 116.4 17.1 135.9 23.1 202.6 167.0 208.3 133.5 166.2

NbO2 2.9 1.2 3.1 1.6 3.1 3.6 2.8 2.7 3.4MoO2 4.2 0.5 2.3 0.2 3.6 0.6 0.8 4.0 2.9

InO 13.8 234.3 0.1 337.3 0.2 1.6 1.0 0.7 1.6Sb2O5 7.4 10.9 1.7 11.3 4.8 32.4 61.2 0.17% 10.0SnO2 0.24% 4.50% 21.7 6.57% 57.7 279.9 255.6 77.3 227.5Cs2O 0.3 0.2 0.2 0.0 0.6 0.5 0.2 0.2 0.2BaO 331.1 75.6 247.3 828.0 831.5 142.0 115.6 213.3 407.4

La2O3 5.7 3.1 6.2 9.6 7.0 10.7 7.5 8.6 7.3Ce2O3 10.6 5.7 11.0 10.7 12.6 13.8 14.5 14.6 13.1Pr2O3 1.6 0.9 1.3 1.7 1.4 1.6 1.6 1.9 1.6Nd2O3 6.5 3.1 5.3 7.0 6.5 9.1 6.3 8.1 7.9Sm2O3 1.1 0.5 0.6 1.2 1.0 1.3 1.0 1.8 1.6Eu2O3 0.9 0.0 1.1 0.3 0.8 0.9 1.0 0.7 0.8Gd2O3 1.8 0.5 1.4 1.1 1.5 2.3 1.9 1.3 1.7Tb2O3 0.1 0.1 0.1 0.2 0.1 0.1 0.1 0.2 0.2Dy2O3 1.0 0.4 0.7 0.9 0.9 1.0 0.9 1.2 1.1Ho2O3 0.2 0.1 0.1 0.2 0.2 0.2 0.2 0.2 0.2Er2O3 0.5 0.2 0.5 0.6 0.6 0.5 0.5 0.9 0.7

Tm2O3 0.1 0.0 0.0 0.1 0.1 0.1 0.1 0.1 0.1Yb2O3 0.5 0.3 0.5 0.6 0.6 0.5 0.8 0.8 0.7Lu2O3 0.1 0.0 0.1 0.1 0.1 0.0 0.1 0.1 0.1HfO2 2.1 0.4 2.2 0.4 4.3 2.2 2.7 2.9 3.0

PbO 0.23% 10.75% 822.1 30.95% 0.36% 0.13% 691.2 0.19% 0.24%

ThO2 1.5 0.6 1.4 0.8 2.7 2.1 2.1 1.8 2.2U3O8 0.8 0.3 0.6 1.5 1.1 0.6 0.8 1.1 0.9

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is a high-lime high-aluminum (HLHA) glass known only from West Africa (lankton et al. 2006). PR715 contains a relatively large amount of potash (K2O) compared with the published analyses of HLHA glass, though it is not too different from the levels found in crucible glass at Ife (lankton et al. 2006: tab. 2). The third type of glass is not represented by a complete bead but only by the white stripes in PR681: this is a lead-silica glass with high concentrations of phosphorus and lime (PbSiPC glass). This glass is most unusual; it may represent the use of the mineral pyromorphite (Pb5[Cl:(PO4)3]: palache et al. 1951: 889–895; an-thony et al. 2000: 482), heated with high levels of lime, as a coloring agent1. The use of pyromorphite in specialty glass manufacture continues to the present day (Shackelford & doreMuS 2008).

We have identified two sub-types of vNC glass among the Kissi beads. PR693 and PR694 have quan-tities of lead (PbO) (see Tab. 1) that far exceed what is expected when lead stannate is added as a yellow coloring agent. Moreover, these beads are blue-green, not yellow. The lead in this vNC-Pb glass may have been added during its initial manufacture or during a subsequent recycling or bead-making process. Work-ing with this leaded glass would have required rather different technological processes than those used with regular vNC glass.

PR682, PR 683, PR685 and PR705 have rather low levels of magnesia (MgO) and to a lesser extent potash (K2O), probably indicative of the use of a different plant ash from that of the majority of the beads, since these magnesia levels are not so low as to warrant identifica-tion as mineral-soda glass. PR683 is also depleted in soda, probably as a result of leaching. We group these four beads (PR682, 683, 685, 705) as sub-type vNC-a (see Tab. 2).

PR712 is the only vNC bead for which the alumina level exceeds that of the lime, an observation that might warrant labeling this as a vNCA glass, an attribution that would be significant since this glass type is often thought to originate in a different part of the world from vNC glass. However, PR712 also has a low level of soda indicating that it is a glass from which some of the soda has been leached by natural chemical weathering processes. Since leaching may affect the quantities of

1 It seems odd that the white stripes of PR680 do not appear to have been made from the same glass. The glass of these stripes is a vNC glass, though with higher concentrations of lead and tin, which are usually indicative of their addition together as a (yellow) coloring agent (lead stannate).

several oxides, including increasing the relative level of alumina (duSSubIeux et al. 2009), caution precludes us from assigning this bead to the vNCA type.

Various minerals were used as coloring agents. The turquoise and blue-green beads were colored with copper, while cobalt, often in combination with copper, was used to color the blue beads. Lead mixed with tin was frequently used as a yellow colorant and opaci-fier; cerussite (PbCO3), which is often associated with manganese (MnO), is a possible lead source. Manga-nese may also have been used as a colorant, as in the purple-colored beads.

SourceS of the glaSS

It is generally and correctly assumed that the chemistry of a glass reflects the geochemistry of the region or regions where the ingredients used in the making of the glass were acquired. Thus, glass manufactured in a particular region will tend to have a distinctive chemical signature that will persist over time, assuming no major changes occur in the choice of raw materials. It is also assumed that once glass has been made, its chemical composition will not change significantly through time. These assumptions generally hold true, but exceptions have been noted; for example, cullet (raw or waste glass) was widely traded across Western Asia, as is evi-dent from the Serçe Limani shipwreck (baSS 2004), as were coloring agents like cobalt (henderSon 1998). In addition glass beads were often made at centers different from, and sometimes even continents away from, glass manufacturing sites so in theory glasses from different sources could have been used in making even a single bead. Glass may also undergo chemical weathering and surface hydration over time, particularly after burial, thereby altering its chemical composition, though in predictable ways (duSSubIeux et al. 2009).

High-alumina high-lime (HLHA) glass is known only from West Africa, where it was manufactured using ingredients and technology very different from those of the rest of the glass-making world (freeStone 2006a). There is good archaeological evidence that this glass was manufactured at Ile-Ife in southern Nigeria from early in the second millennium AD if not before (lankton et al. 2006). In addition to the single bead (PR715) of this glass found in the present study, beads of HLHA glass have been discovered at several West African sites, though HLHA glass is comparatively rare at most sites, which are dominated, like Kissi, by vNC glass (ibid.). We cannot assign a reliable date to the HLHA bead from Kissi 13 because the graves in this cemetery had been disturbed prior

100


to archaeological excavation, though a late first millen-nium AD age seems probable (see above).

The white stripes in PR681, as noted above, may represent the use of the mineral pyromorphite. Two beads made from a glass of similar composition, but of a black color and very heterogeneous, have been analyzed from the site of al-Basra in Morocco in de-posits of the late 10th century AD (robertShaw et al. in press). Pyromorphite is a secondary lead mineral found in the oxidized zones of lead deposits (MIndat.org 2008). It is, thus, widely distributed and probably often overlooked in geological surveys. Therefore, it may be of little help in finding the provenance of the glass in which it occurs.

Soda-lime-silica glass was manufactured in Meso-potamia and Egypt as early as the 2nd millennium BC and continued to be made across Western Asia and the Mediterranean until modern times. However, from the mid-1st millennium BC until the late 1st millennium AD this glass was fluxed with mineral soda (natron or trona) rather than plant ash in the Mediterranean and Syria-Palestinian regions (freeStone 2005). Nevertheless, plant ash (vNC) glass continued to be manufactured east of the Euphrates for most of the 1st millennium AD (SMIth 1963; freeStone 2006b). In the Syria-Pal-estinian region and eastern Mediterranean plant ash (v) replaced mineral soda as the source of the alkali used in glass manufacture beginning in the late 8th or early 9th century AD when political unrest in Egypt disrupted the supply of natron (whItehouSe 2002; henderSon et al. 2004; Shortland et al. 2006). More generally, it

seems that in Western Asia in the 1st millennium AD large quantities of glass were manufactured from raw materials at a small number of primary workshops that supplied numerous secondary workshops with raw glass that was turned into vessels, beads and other artifacts (freeStone 2005, 2006b). Raw glass (cullet) was thus widely traded in the ancient world.

Where in Western Asia was the vNC glass found at Kissi manufactured? Given the disturbed context of the Kissi 13 cemetery, the beads can be dated with confidence only broadly to the 1st millennium AD. If they date to the last two centuries of the 1st millennium and are thus Islamic, they could in theory have been made of plant-ash glass manufactured anywhere in Western Asia. If they date earlier in the 1st millennium and are thus attributable to the Sasanian, the glass was most probably manufactured in a workshop or work-shops east of the Euphrates. Fortunately, comparisons of the chemistry of the Kissi beads with glasses from Western Asia allow us to place the origin of most of the Kissi vNC glass to the east of the Euphrates, with the vNC-a subtype probably manufactured in the Syria-Palestinian or more broadly, eastern Mediterranean region (Fig. 2).

Several chemical analyses of Sasanian glass have been published (notably brIll 1999; MIrtI et al. 2008), while there are numerous analyses of Islamic glass of the late 1st and early 2nd millennium AD (notably brIll 1995a, 1999; freeStone 2002, 2006b; freeStone et al. 2000; henderSon et al. 2004). On the basis of many of these analyses, freeStone (2006b: fig. 2) has argued

Fig. 2. Map of glass workshops and other sites mentioned in the text.

101


that Sasanian glass can be distinguished from Islamic glass of the Syria-Palestinian region by the fact that the former is characterized by quantities of both K2O and MgO generally in excess of 3.5 %, whereas the latter has quantities of these oxides between 2 and 3.5 %. Many, but not all, of the analyzed glass samples from the Islamic city of Nishapur in Iran also contain high levels of K2O and MgO (brIll 1995a). This pattern is revealed to some extent in Figure 3, where “East” designates the samples from east of the Euphrates, which comprise all the Sasanian samples plus the Is-lamic glasses from Nishapur, and “West” the Islamic glasses from the Syria-Palestinian region and the east-ern Mediterranean (see Tab. 4 for the sources of the comparative data). freeStone (2006b) has suggested that the differences in oxide levels may be explained either by the use of different plant species burnt to make the ash or by the fact that the high magnesia levels in the eastern glasses reflect the magnesia-rich alluvium of the Euphrates and Tigris valleys.

The pattern in Figure 3 is admittedly not entirely clear; there are several samples, which we discuss be-low, that do not conform to the expected pattern. The Kissi vNC samples are also characterized by relatively high Al2O3 and low CaO levels, whereas the western and eastern comparative glass samples are generally distinguishable by their lower or higher CaO levels, though again the pattern is not entirely clear (Fig. 4).

We can begin to clarify matters by combining Figures 3 and 4 by means of calculating the ratios of pairs of oxides and examining the data by site and period (Sasanian/Islamic), which we do in Figures 5 and 6.

Most of the Kissi beads have high Al2O3 levels and thus low ratios of lime to alumina (~1.5–3), compa-rable to some of the Sasanian glass and to a cluster of glasses evident in Figure 6 deriving from the sites of Nishapur and al-Raqqa. In the case of Sasanian glass, MIrtI et al. (2008) have identified two types of vNC glass in their samples from Seleucia and Veh Ardašīr; the Kissi beads, excluding the vNC-a subtype, are a good match with their Type 1 in terms not only of the ratios of the oxides shown in Figure 5, but also in terms of phosphorus levels (P2O5 >0.2 %). In the case of the Islamic glass, two major clusters are evident in Figure 6, distinguished primarily on the basis of the lime/alumina ratio. Both Nishapur and al-Raqqa have two clusters of vNC glasses, one with high and one with low alumina, while most of the remaining samples from the Syrian-Palestinian region, including the Serçe Limani shipwreck, have high lime/alumina and low magnesia/potash ratios. This pattern probably reflects first the use of two different silica sources, sand for the high alumina glass and quartz pebbles for the low alumina glass (see below), and second the use of different plant species in the preparation of the plant ash.

Fig. 3. Reduced composi-tions of Kissi vNC and com-parative glasses – magnesia and potash.

102


Fig. 4. Reduced compositions of Kissi vNC and comparative glasses – lime and alumina.

Fig. 5. Reduced compositions of Kissi vNC and Sasanian glasses.

103


Most of the Kissi vNC beads, excluding the vNC-a subtype, fit best with the Sasanian samples and with the high alumina glasses from Nishapur, also east of the Euphrates, as well as with those from the primary glass workshop at al-Raqqa in Syria. In the al-Raqqa case, most of the Kissi vNC glass appears to be similar to its Type 4 plant ash glass. henderSon et al. (2004: 457–458) argue that the type 4 al-Raqqa glass was made by adding plant-ash to sand, with the high levels of alumina, correlated with the levels of titanium oxide and iron2, being indicative of the silica source but not the alkali. Moreover, the comparatively broad ranges in the quantities of various oxides in al-Raqqa Type 4 glass also indicated that this glass was “the result of experimentation with raw ingredients and of the subsequent recycling or reuse of cullet (of Type 4) resulting from such experimentation”, sug-gesting an early stage in the development of Islamic plant-ash glass (henderSon et al. 2004: 457). Al-Raqqa Type 4 glass is also very similar in composi-tion to colored, but not colorless, plant ash glass from

2 For the Kissi vNC glasses, excluding the vNC-a and vNC-Pb subtypes, Al2O3, TiO2, and Fe2O3 are all significantly correlated with each other at p<0.001.

Nishapur, suggesting that a variant of the sand-plant ash recipe used at al-Raqqa was employed at Nishapur (henderSon et al. 2004: 463; see henderSon 2003 for further discussion). However, we would argue that Nishapur and/or Sasanian glass is a better match for the Kissi samples than the Type 4 glass at al-Raqqa because the latter exhibits a negative correlation be-tween alumina and magnesia, which is not the case for the Kissi vNC glasses. In this regard, the Kissi vNC beads perhaps reflect a less experimental and more mature phase of primary glass manufacture than is the case for al-Raqqa Type 4 glass. Furthermore, the colorless/white beads of vNC glass at Kissi are a good chemical match for the colorless glass at Nishapur, since both are characterized by small quantities of alumina, indicative of a quartz rather than sand source for the silica component of these glasses.

While the regular vNC glass beads from Kissi appear to have been made from glass manufactured east of the Euphrates, the four specimens of the vNC-a subtype, with their smaller quantities of magnesia and potash, are much more similar to the Islamic glasses from the Syria-Palestinian and eastern Mediterranean region, particularly perhaps the glass recovered from the Serçe Limani shipwreck.

Fig. 6. Reduced compositions of Kissi vNC and Islamic glasses. Note that the scales differ from those of Fig. 5.

104


There remain four Kissi beads of vNC glass that merit further discussion. Two of these beads (PR693 and PR694) comprise the leaded sub-group of vNC glass mentioned earlier. The two beads are chemically almost identical (Fig. 7), indicating that they were made from the same batch of glass, perhaps even the same drawn tube that was segmented into beads. The only other examples of this glass type found in Africa and known to us are a few beads, mostly also blue-green in color and probably also dating to the late first millennium AD, from Essouk in Mali (lankton 2008; robertShaw 2008) and one bead from Jenné-jeno, also in Mali (sample #5527; brIll 1995b). There are also two artifacts of this glass type, though with even higher concentrations of lead, from the contempora-neous site of al-Basra in Morocco (robertShaw et al. in press). Lead in combination with tin was often added to glass as a yellow-coloring agent, lead stan-nate; for example, a sample (#5367; brIll 1999, II: 158) of yellow opaque glass from the Sasanian site of Ctesiphon contains about 20 % lead, but we know of no examples of leaded vNC glass from Western Asia where the lead was not added to color glass yellow. However, the reduced compositions, i.e. excluding the lead component, of the glass from which PR693 and 694 were made are broadly similar to high alumina plant-ash glass from east of the Euphrates. Perhaps lead was added during the recycling of a batch of plant ash glass.

PR685 is also an unusual vNC glass because it contains an anomalously high concentration (0.17 %) of antimony (Sb2O5). Antimony was used either in combi-nation with lead as a yellow colorant or as an opacifier of mineral soda glass in the late first millennium BC, being first combined with manganese (MnO) and then replaced by it in Western Asia in the first centuries AD (Sayre & SMIth 1963; henderSon 1985: 284). Since PR685 also contains 0.3 % manganese, it may date to very early in the first millennium AD, though one would expect such an early glass to have been fluxed with mineral soda rather than plant ash.

The final unusual specimen of vNC glass from Kissi is PR710; this has a surprisingly large quantity (0.18 %) of zirconia (ZrO2). This could be due to the addition of silica from sand which possessed a signifi-cant amount of detrital (sedimentary) zircons. These would be common in sand derived from the erosion of continental cores of uplifted, igneous rock, suggestive of a source near a plate boundary.

Several researchers have attempted to character-ize different cobalt-rich ores based on the minerals associated with the cobalt (CoO) and thereby pinpoint the sources of the cobalt used as a colorant in ana-lyzed glass. Additive levels of cobalt are present in many of the Kissi beads, including the single bead of HLHA glass. This and all the vNC beads with additive

1

10

100

1000

10000

100000

1000000

Na

Ca K

Mg Al Ti Sr V Cr

Zr Li Rb La Ce Pr

Nd

Sm Eu

Gd Tb Dy

Ho Er

Tm Yb Lu

PR693

PR694

Chondrite-normalized area

Fig. 7. Logarithmic graph of chemical elements in the leaded vNC glass beads PR693 and 694, with chondrite-normalized REE values (MagnavIta 2006: fig. 88). Apart from a Terbium (Tb) anomaly, the graphs are almost identical.

105


cobalt also contain greater quantities of nickel (NiO)3, but not of zinc (ZnO)4, thus likely ruling out use of the better-known European and Western Asian cobalt sources (gratuze et al. 1992; freeStone & Stapleton 1998; henderSon 1998). There are also possible, but apparently chemically little-known, cobalt sources within West Africa (lankton et al. 2006: 135). HLHA glass results from other West African sites, reported many years ago by davISon (1972: 256), exhibit a correlation between manganese (MnO) and cobalt at a ratio of about nine to one (lankton et al. 2006: 135); this ratio in our single HLHA glass specimen is 7.2:1.

Several of the Kissi beads, are morphologically very similar to beads, also dated to the late first mil-lennium AD, found at sites in southern Africa, notably in the Shashe-Limpopo area, as well as in West Africa, notably at Igbo-Ukwu in eastern Nigeria (Shaw 1970). Many of these tubular to cylindrical beads are rela-tively large for beads made by the technology of being drawn, rather than wound; they are mostly translucent to opaque dark blue or yellow in color but blue-green and green occur as well (wood 2000: 79). In southern Africa they are termed “Zhizo” beads after the first site at which they were excavated. All chemically analyzed specimens, including those from Kissi, were manu-factured from vNC glass. Lead isotope analyses of a sample of these beads from Igbo-Ukwu and southern Africa revealed that some of them have lead isotope ratios not incompatible with lead ore deposits in Iran (robertShaw et al. in prep.). These isotope data, in combination with the elemental analyses, strengthen the case for a Western Asian provenance for much of the vNC glass and provide encouragement for further investigation of the possibility of a glass source or sources east of the Euphrates, likely in Iran.

3 T=3.205; df=36; p<0.01

4 T=0.942; df=36; p>0.05

SuMMary

Chemical analysis of 37 glass beads recovered from the cemetery of Kissi 13 in Burkina Faso reveals the presence of three major types of glass. One bead was manufactured from a high-alumina, high-lime glass known to have been made in West Africa (lankton et al. 2006). Another bead has white stripes that probably result from the use of the mineral pyromorphite as a coloring agent. Otherwise, all the other beads were made from soda-lime glass, in which a plant ash was the source of the alkali used as a flux. This glass was almost certainly made in Western Asia, with most speci-mens being made of glass that was manufactured east of the Euphrates, while those of the vNC-a subtype were made from glasses manufactured further west in the Islamic world. Two beads of the vNC glass contain much greater quantities of lead; these beads may have been made by recycling Western Asian glass and add-ing lead to it. However, these two blue-green beads show no obvious morphological or technological dif-ferences from most of the other analyzed vNC beads; lead isotope analysis might shed further light on their origins. Finally, there are two vNC beads, one with a comparatively large amount of antimony and the other with considerable zirconia, that may respectively rep-resent a very old bead at Kissi and the use of sand from uplifted igneous rocks.

acknowledgeMentS

Jim Lankton made valuable comments on an earlier version of this paper, though he should not be held responsible for its content. The research on which this paper is based was funded by the National Science Foundation (BCS-0209681).

106


AN

IDSa

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Col

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60.9

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0.84

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0.4

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125.

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26.8

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0%13

.63%

0.28

%14

.27%

636.

725

8.7

30.2

248.

80.

44%

3.9

12.8

206.

059

5.4

236.

13.

066

2.5

9.8

AN

IDZ

rO2

NbO

2M

oO2

InO

Sb2O

5Sn

O2

Cs 2O

BaO

La 2O

3C

e 2O3

Pr2O

3N

d 2O3

Sm2O

3E

u 2O3

Gd 2O

3T

b 2O3

Dy 2O

3H

o 2O3

Er 2O

3T

m2O

3Y

b 2O3

Lu 2O

3H

fO2

PbO

ThO

2U

3O8

PR68

616

6.2

3.4

2.9

1.6

10.0

227.

50.

240

7.4

7.3

13.1

1.6

7.9

1.6

0.8

1.7

0.2

1.1

0.2

0.7

0.1

0.7

0.1

3.0

0.24

%2.

20.

9PR

706

116.

53.

12.

415

.13.

40.

33%

0.4

232.

87.

212

.91.

66.

40.

90.

20.

60.

21.

00.

20.

60.

10.

60.

12.

02.

19%

2.0

0.8

PR70

717

3.4

2.9

2.0

0.2

0.0

6.8

0.1

307.

46.

810

.41.

44.

70.

90.

11.

30.

21.

00.

20.

60.

10.

70.

12.

893

.02.

00.

8PR

708

108.

42.

73.

68.

67.

60.

21%

0.2

247.

15.

89.

91.

24.

80.

80.

20.

90.

21.

00.

20.

50.

10.

70.

12.

12.

03%

1.8

0.8

PR70

910

7.7

2.8

4.2

5.4

8.9

0.10

%0.

136

9.1

7.5

13.3

1.7

6.8

1.2

0.0

0.7

0.2

1.2

0.2

0.7

0.1

0.9

0.1

2.1

0.85

%1.

60.

9PR

710

####

2.3

3.6

3.6

5.3

686.

60.

023

7.7

5.8

11.2

1.4

4.9

0.9

0.0

0.6

0.1

1.0

0.2

0.6

0.1

0.8

0.1

5.2

0.55

%1.

80.

9PR

712

197.

54.

22.

15.

82.

70.

13%

0.0

706.

87.

812

.01.

46.

31.

30.

00.

50.

21.

10.

20.

70.

10.

70.

13.

50.

62%

2.7

0.9

PR69

710

4.4

3.0

1.2

3.2

1.4

499.

20.

615

2.2

5.6

9.5

1.1

4.5

0.6

0.1

0.9

0.1

0.6

0.1

0.4

0.0

0.4

0.1

1.6

0.87

%1.

51.

0PR

699

91.8

2.9

2.2

9.3

6.5

0.39

%0.

134

3.7

6.9

13.9

1.7

7.1

1.2

0.4

1.2

0.2

1.1

0.2

0.6

0.1

0.8

0.1

2.2

2.99

%1.

80.

8PR

713

109.

52.

53.

20.

80.

765

.50.

032

9.6

6.1

10.8

1.4

5.7

1.1

0.0

0.6

0.1

0.8

0.1

0.4

0.1

0.7

0.1

2.0

530.

31.

80.

9PR

714

114.

02.

13.

24.

33.

091

7.0

0.1

326.

05.

910

.21.

36.

01.

20.

01.

30.

21.

00.

20.

60.

10.

50.

11.

70.

84%

1.5

0.7

PR71

112

5.0

2.8

3.2

4.3

3.5

850.

00.

127

4.1

8.0

13.5

1.6

6.9

1.4

0.0

0.7

0.1

0.9

0.2

0.6

0.1

0.7

0.1

1.9

0.70

%1.

71.

0PR

695

161.

13.

91.

50.

20.

545

.20.

230

5.4

9.7

17.3

2.3

7.6

1.6

0.3

1.5

0.3

1.1

0.2

0.7

0.1

0.8

0.2

2.5

294.

52.

51.

0PR

698

150.

43.

91.

85.

45.

098

7.3

0.3

267.

38.

015

.21.

87.

71.

00.

42.

20.

31.

00.

20.

60.

10.

60.

12.

20.

86%

2.2

1.0

PR69

617

3.5

3.9

0.9

2.0

0.5

232.

20.

326

1.1

7.4

12.1

1.6

5.2

1.2

0.3

1.1

0.2

1.0

0.2

0.6

0.1

0.7

0.1

2.7

346.

42.

41.

1PR

680

116.

42.

94.

213

.87.

40.

24%

0.3

331.

15.

710

.61.

66.

51.

10.

91.

80.

11.

00.

20.

50.

10.

50.

12.

10.

23%

1.5

0.8

PR68

113

5.9

3.1

2.3

0.1

1.7

21.7

0.2

247.

36.

211

.01.

35.

30.

61.

11.

40.

10.

70.

10.

50.

00.

50.

12.

282

2.1

1.4

0.6

PR68

420

8.3

2.8

0.8

1.0

61.2

255.

60.

211

5.6

7.5

14.5

1.6

6.3

1.0

1.0

1.9

0.1

0.9

0.2

0.5

0.1

0.8

0.1

2.7

691.

22.

10.

8PR

692

186.

02.

90.

618

.927

.50.

44%

0.1

100.

27.

613

.81.

76.

81.

10.

40.

80.

10.

60.

10.

40.

10.

50.

12.

90.

49%

1.9

0.8

PR71

627

1.2

3.1

0.6

1.2

46.8

331.

90.

010

2.6

9.6

18.3

2.0

9.3

1.3

0.0

0.6

0.1

1.1

0.2

0.6

0.1

0.6

0.1

5.2

358.

82.

60.

9PR

680-

whi

te17

.11.

20.

523

4.3

10.9

4.50

%0.

275

.63.

15.

70.

93.

10.

50.

00.

50.

10.

40.

10.

20.

00.

30.

00.

410

.75%

0.6

0.3

PR68

921

0.8

2.7

4.9

5.7

12.5

0.12

%0.

135

5.0

8.6

14.3

1.8

7.2

1.2

0.6

1.4

0.1

1.1

0.2

0.6

0.1

0.7

0.1

3.6

0.45

%2.

30.

9PR

690

209.

22.

53.

241

.415

.71.

41%

0.1

313.

98.

512

.91.

45.

91.

10.

61.

70.

10.

80.

20.

50.

10.

80.

13.

60.

36%

2.2

0.7

PR69

119

7.7

2.8

4.3

8.8

7.0

0.50

%0.

034

4.3

7.7

14.8

1.7

7.7

1.3

0.8

1.6

0.1

0.9

0.2

0.5

0.1

0.7

0.1

4.0

0.35

%2.

10.

8PR

687

81.6

2.3

1.7

26.2

4.0

0.55

%0.

352

1.9

6.0

12.0

1.4

5.7

1.2

0.5

1.2

0.1

0.8

0.2

0.6

0.1

0.7

0.1

1.8

4.36

%1.

60.

7PR

688

115.

82.

41.

411

.94.

00.

34%

0.5

381.

06.

412

.01.

55.

71.

20.

81.

70.

21.

10.

20.

70.

10.

80.

12.

33.

53%

2.0

0.9

PR70

011

5.2

2.6

1.3

27.2

2.4

0.59

%0.

232

6.0

6.6

12.3

1.5

6.5

1.0

0.4

1.1

0.2

1.0

0.2

0.6

0.1

0.7

0.1

1.9

5.92

%1.

70.

7PR

701

76.6

1.6

1.1

25.5

0.9

0.56

%0.

241

9.7

6.0

12.3

1.4

5.6

1.1

0.3

0.9

0.2

0.8

0.2

0.5

0.1

0.6

0.1

1.6

5.80

%1.

50.

7PR

702

153.

54.

01.

915

.83.

60.

61%

0.2

369.

38.

414

.22.

07.

21.

30.

31.

30.

21.

20.

20.

60.

10.

60.

12.

54.

00%

1.9

0.9

PR70

388

.82.

71.

923

.84.

20.

73%

0.1

362.

78.

414

.11.

77.

01.

20.

61.

40.

20.

90.

20.

70.

10.

60.

11.

84.

64%

1.7

0.8

PR70

413

3.3

2.6

1.9

18.2

5.1

0.45

%0.

239

0.0

7.3

12.3

1.6

5.7

1.3

0.2

0.9

0.2

0.9

0.2

0.5

0.1

0.6

0.1

2.2

4.35

%1.

70.

7PR

693

103.

62.

90.

478

.710

6.5

1.79

%0.

221

4.6

6.6

11.8

1.4

5.9

1.1

0.3

1.0

0.1

1.0

0.2

0.6

0.1

0.6

0.1

2.0

19.1

1%2.

10.

9PR

694

89.6

2.7

0.3

84.2

60.4

1.60

%0.

221

7.1

6.5

11.0

1.4

6.2

1.0

0.3

0.8

0.2

0.9

0.2

0.6

0.1

0.6

0.1

1.7

18.5

7%1.

70.

8PR

682

202.

63.

13.

60.

24.

857

.70.

683

1.5

7.0

12.6

1.4

6.5

1.0

0.8

1.5

0.1

0.9

0.2

0.6

0.1

0.6

0.1

4.3

0.36

%2.

71.

1PR

683

167.

03.

60.

61.

632

.427

9.9

0.5

142.

010

.713

.81.

69.

11.

30.

92.

30.

11.

00.

20.

50.

10.

50.

02.

20.

13%

2.1

0.6

PR68

513

3.5

2.7

4.0

0.7

0.17

%77

.30.

221

3.3

8.6

14.6

1.9

8.1

1.8

0.7

1.3

0.2

1.2

0.2

0.9

0.1

0.8

0.1

2.9

0.19

%1.

81.

1PR

705

164.

63.

35.

232

.322

.80.

73%

1.2

0.11

%7.

713

.51.

87.

31.

20.

30.

90.

21.

00.

20.

60.

10.

60.

12.

711

.42%

2.0

0.9

PR71

525

.23.

20.

80.

00.

07.

317

.832

5.9

4.0

27.1

1.3

5.1

1.1

0.1

0.6

0.1

0.6

0.1

0.5

0.0

0.3

0.0

0.5

72.3

1.1

1.2

PR68

1-w

hite

23

.11.

60.

233

7.3

11.3

6.57

%0.

082

8.0

9.6

10.7

1.7

7.0

1.2

0.3

1.1

0.2

0.9

0.2

0.6

0.1

0.6

0.1

0.4

30.9

5%0.

81.

5

Tab.

1. T

he c

hem

ical

com

posi

tions

of b

eads

from

Kis

si (w

here

% is

not

indi

cate

d, th

e va

lues

are

giv

en in

ppm

)

108


ANID BEAD ID Color Na2O* MgO* Al2O3* SiO2* K2O* CaO* Fe2O3* Glass Type

PR686 7 blue 13.16 4.50 4.15 66.17 3.55 7.20 1.27 vNCPR706 30 blue 14.46 5.28 3.87 63.63 3.93 7.90 0.92 vNCPR707 31 blue 13.67 4.24 3.32 67.34 3.25 7.21 0.98 vNCPR708 32 blue 13.55 4.50 3.33 67.87 3.33 6.48 0.95 vNCPR709 33 blue 15.28 5.59 3.54 63.53 3.95 7.17 0.93 vNCPR710 34 blue 14.41 4.80 3.33 66.25 3.58 6.74 0.89 vNCPR712 36 blue 6.40 3.89 6.60 72.95 2.60 5.78 1.78 vNCPR697 21 light green 14.02 4.07 4.04 66.37 3.95 6.78 0.76 vNCPR699 23 olive green 13.91 5.49 3.14 67.30 3.83 5.66 0.68 vNCPR711 35 pale blue 10.85 5.76 4.02 68.54 3.77 6.03 1.04 vNCPR713 37 pale blue 13.10 4.65 3.21 67.67 4.31 6.20 0.85 vNCPR714 38 pale blue 12.41 3.89 2.98 70.52 3.30 6.21 0.69 vNCPR695 19 pale blue-green 10.08 3.79 3.56 70.36 3.58 7.84 0.78 vNCPR698 22 pale green 12.10 3.68 4.31 67.60 4.07 7.24 1.01 vNCPR696 20 pale greenish-blue 12.03 4.72 3.98 69.46 3.32 5.66 0.82 vNCPR680 1 purple 13.41 4.16 3.02 69.00 2.84 6.99 0.59 vNCPR681 2 purple 10.60 3.49 3.21 72.01 2.88 7.23 0.57 vNCPR684 5 turquoise 10.90 4.10 2.41 71.53 2.98 7.52 0.56 vNCPR692 14 turquoise 12.79 3.93 1.84 72.37 3.04 5.48 0.55 vNCPR716 40 turquoise 13.71 5.27 2.15 65.54 3.88 8.88 0.57 vNCPR680-white 1 white 16.51 5.79 1.29 66.96 3.21 5.78 0.45 vNCPR689 10 white/colorless 12.61 5.48 1.94 69.99 3.50 5.95 0.52 vNCPR690 11 white/colorless 13.14 5.24 2.00 69.54 3.28 6.34 0.46 vNCPR691 12 white/colorless 11.64 5.77 2.15 70.55 3.64 5.79 0.46 vNCPR687 8 yellow 14.47 3.54 2.92 68.99 3.82 5.65 0.61 vNCPR688 9 yellow 12.60 5.03 3.43 68.49 4.00 5.61 0.85 vNCPR700 24 yellow 14.87 4.58 3.55 66.51 3.24 6.62 0.62 vNCPR701 25 yellow 14.94 4.47 2.90 68.12 3.36 5.60 0.61 vNCPR702 26 yellow 13.78 3.62 3.51 68.05 3.86 6.46 0.71 vNCPR703 27 yellow 10.11 4.28 3.77 71.68 3.22 6.13 0.81 vNCPR704 28 yellow 11.82 4.01 3.07 71.44 3.10 5.99 0.55 vNC

PR693 15 blue-green 12.43 4.79 4.98 65.86 2.49 8.62 0.83 vNC-PbPR694 16 blue-green 12.60 4.12 4.21 67.67 2.48 8.16 0.77 vNC-Pb

PR682 3 light olive green 12.45 2.05 2.28 69.86 2.85 9.61 0.90 vNC-aPR683 4 turquoise 8.01 2.67 2.83 76.11 2.65 7.00 0.74 vNC-aPR685 6 blue 11.34 3.30 2.94 69.48 2.59 9.56 0.79 vNC-aPR705 29 yellow 12.82 2.76 2.78 68.07 3.28 9.19 1.09 vNC-a

PR715 39 grayish blue 2.06 0.15 16.92 56.78 11.00 12.47 0.63 HLHA

PR681-white 2 white 0.44 2.56 4.53 61.51 0.58 29.46 0.91 PbSiPC

Tab. 2. Reduced compositions of the Kissi glass beads.

Tab. 3. Means, standard deviations, and ranges of the reduced compositions of the vNC glass, including sub-types.

Na2O* MgO* Al2O3* SiO2* K2O* CaO* Fe2O3*

mean 12.62 4.36 3.26 68.74 3.37 6.87 0.78s.d. 1.97 0.90 0.97 2.59 0.49 1.17 0.26min 6.40 2.05 1.29 63.53 2.48 5.48 0.45max 16.51 5.79 6.60 76.11 4.31 9.61 1.78

109


Site Location Date (centuries AD) Reference Number of samples

Fustat Egypt 9th–13th brIll 1999: II: 168–170 20Banias Israel 11th–13th freeStone et al. 2000 17Al-Raqqa Syria late 8th–early 9th henderSon et al. 2004 102Siraf Iran 9th–10th brIll 1999: II: 173 9Tyre Lebanon 10th–11th freeStone 2002 10Nishapur Iran 9th–11th brIll 1999: II: 162–166 47Ramla Israel 9th–10th freeStone 2006b 6Serçe Limani Turkey late 10th-early 11th brIll 1999: II: 178–187 95Seleucia Iraq 1st–3rd MIrtI et al. 2008 1Veh Ardašīr Iraq 3rd–6th MIrtI et al. 2008 26Jezaziyat Iraq 2nd–6th brIll 1999: II: 152–153 21Tell umm Jirin Iraq 5th–6th brIll 1999: II: 154 5Choche Iraq 3rd–early 5th brIll 1999: II: 155–156 11Ctesiphon Iraq 3rd–8th brIll 1999: II: 157–158 15

Tab. 4. Comparative Western Asian plant-ash glass samples.

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Glass beads from Kissi (Burkina Faso): chemical analysis and archaeological interpretation

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