THE TRADING OF ANCIENT GLASS BEADS: NEW ANALYTICAL DATA FROM SOUTH ASIAN AND EAST AFRICAN SODA–ALUMINA GLASS BEADS*

The occurrence of similar glass beads at archaeological sites in Africa and Asia bears witness to the trade relationship between the two continents. This paper reports elemental analysis results from a recent in‐depth laser ablation – inductively coupled plasma – mass spectrometry (LA–ICP–MS) study of a group of archaeological glass beads with a specific alumina‐rich composition from East Africa, India and Sri Lanka. Based on the concentrations of the trace elements, two different subgroups were identified. One subgroup occurs at early periods (fourth century bce to fifth century ace ) in South India and Sri Lanka. The second subgroup appears at later dates in Africa and was identified at different Kenyan sites dated from the ninth to the 19th century ace , and at the contemporaneous site of Chaul in western India.     

COMPLEMENTARY COMPOSITIONAL ANALYSIS OF FORMATIVE PERIOD CERAMICS FROM THE TEOTIHUACAN VALLEY

During the Classic Period, Teotihuacan was an economic centre of central Mexico, but little is known about the development of this system. This paper presents a pilot study in multi‐method analysis of Formative Period (1500/1400 bc –ad 150) ceramics from the Teotihuacan Valley. Pottery was characterized by instrumental neutron activation analysis, laser ablation inductively coupled plasma mass spectrometry, thermal ionization mass spectrometry and petrography. It appears that most pottery was made from local raw materials that differ from later Postclassic materials. Some inter‐village interaction is suggested by stylistic choices, and one settlement had a group of ceramics made from unequivocally distinct raw materials. The study demonstrates how complementary methods can be used to draw greater anthropological meaning from compositional differences.     

AN ARCHAEOMETRIC STUDY OF MEDIEVAL GLASS FROM THE FIRST BULGARIAN CAPITAL,PLISKA (NINTH TO TENTH CENTURY AD)

Glass finds from the first Bulgarian capital, Pliska, have been analysed by instrumental neutron activation analysis. The analytical data, together with previous results from analysis of glass samples from the second Bulgarian capital, Preslav, were subjected to cluster and discriminant analysis. The local origin of part of the analysed samples was proven and some conclusions about the technology of production were possible.     

ROMAN AND MEDIEVAL GLASS FROM THE ITALIAN AREA: BULK CHARACTERIZATION AND RELATIONSHIPS WITH PRODUCTION TECHNOLOGIES*

Compositional investigations were performed on 81 Roman and medieval glass fragments (first to 14th centuries ad ) from four Italian archaeological sites. The samples were soda–lime–silica in composition, with natron as flux for the Roman and early medieval glass samples, and with plant ash as flux for the late medieval ones. The varying colours are due to the differing FeO, Fe ₂ O ₃ , MnO and Sb ₂ O ₃ contents. Hierarchical cluster analysis identified six compositional groups related to age, which were compared with those found in the literature. In this way, technological continuity from the Roman to the early medieval period and the appearance of plant ash technology in the ninth century, 200 years in advance of the period previously believed, are demonstrated.     

STAINING OF ARCHAEOLOGICAL GLASS FROM MANGANESE‐RICH ENVIRONMENTS*

It has been suggested that both internal and external sources of manganese may produce the black or brown staining that often occurs in buried archaeological glass. Modern potash glass of a manganese‐free medieval composition was scratched, etched and immersed in an aqueous solution containing dissolved manganese. After several weeks, immersion samples were sectioned and examined by SEM–EDX. Manganese was shown to be present in fissures and cracks within in the glass, where alkali had been depleted. Manganese from an external source is capable of blackening buried medieval potash glass.     

CHEMICAL AND MINERALOGICAL CHARACTERIZATION OF SASANIAN AND EARLY ISLAMIC GLAZED CERAMICS FROM THE DEH LURAN PLAIN,SOUTHWESTERN IRAN*

One hundred and seventy‐five glazed ceramics from Sasanian and Early Islamic period sites located on the Deh Luran Plain in southwestern Iran were examined by instrumental neutron activation analysis for characterizing differences in ceramic pastes and by laser‐ablation inductively coupled plasma mass‐spectrometry for identifying the constituents of the ceramic glazes. The results of the analysis reveal that alkaline‐based glazed ceramics have paste compositions that are distinct from contemporary and later ceramics decorated with alkaline–low‐lead and lead‐based glazes.     

THE PROVENANCE OF OBSIDIAN ARTEFACTS FROM THE WĀDĪ ATH‐THAYYILAH 3 NEOLITHIC SITE (EASTERN YEMEN PLATEAU) BY LA–ICP–MS

The geological sources of obsidian in the Red Sea region provide the raw material used for the production of obsidian artefacts found in prehistoric sites on both sides of the Red Sea, as far afield as Egypt, the Persian Gulf and Mesopotamia. This paper presents the chemical characterization of five obsidian geological samples and 20 prehistoric artefacts from a systematically excavated Neolithic settlement in highland Yemen. The major element concentrations were determined by SEM–EDS analysis and the trace element concentrations were analysed by the LA–ICP–MS method, an almost non‐destructive technique capable of chemically characterizing the volcanic glass. A comparison of archaeological and geological determinations allows the provenance of the obsidian used for the Neolithic artefacts to be traced to definite sources in the volcanic district of the central Yemen Plateau.     

NEUTRON ACTIVATION ANALYSIS OF AD 1660–1930 EUROPEAN COPPER-COLOURED BLUE GLASS TRADE BEADS FROM ONTARIO,CANADA

Blue glass trade beads from well-dated late seventeenth- to early twentieth-century sites and collections have been analysed non-destructively by instrumental neutron activation analysis. The beads display enough variations in their elemental contents to allow us to characterize the different chemistries. The implication of these results is that similar chemical analyses of blue beads from undated archaeological sites may be used to help date the sites, since each bead chemistry has a specific earliest period.     

CHEMICAL ANALYSES OF GLASS BEADS FOUND IN TWO SARMATIAN BURIALS*

The chemical compositions of 14 glass beads from two Early Sarmatian-period burials were determined. Al, Ca, Fe, Mg, K, Na, and Si were measured by electron probe microbeam analysis, while the Co, Cu, Ga, Mn, Ni, Pb, Rb, Sr, Th, Ti, Y, Zn, and Zr contents were measured using energy dispersive X-ray fluorescence. All the beads can be classed as low-magnesia soda-lime-silica glasses. The blue glass beads examined in this study were coloured with Co and Cu containing minerals. Cluster analysis and principal components analysis suggest that two distinct glass recipes were used to manufacture these beads.     

COLOUR ATTRIBUTES OF MEDIEVAL WINDOW PANES: ELECTRON PARAMAGNETIC RESONANCE AND PROBE MICROANALYSES ON STAINED GLASS WINDOWS FROM PAVIA CARTHUSIAN MONASTERY*

Stained glass windows from the Carthusian Monastery of Pavia, dating back to the 15th century, were studied by combining two analytical techniques: electron probe micro‐analysis (EPMA) and electron paramagnetic resonance (EPR). Chemical compositions and oxidation states of the transition ions, present as minor elements, were investigated by EPMA and EPR, respectively, in order to ascertain the role played by chromophorous ions in the glass coloration. The investigated glass can be defined as K–Ca glass, and the panes with red, green and blue colours were produced using flashing techniques.     

DEEPLY COLOURED AND BLACK GLASS IN THE NORTHERN PROVINCES OF THE ROMAN EMPIRE: DIFFERENCES AND SIMILARITIES IN CHEMICAL COMPOSITION BEFORE AND AFTER ad 150*

In this work we attempt to elucidate the chronological and geographical origin of deeply coloured and black glass dating between 100 bc and ad 300 on the basis of their major and trace element compositions. Samples from the western and eastern parts of the Roman Empire were analysed. Analytical data were obtained by means of a scanning electron microscope – energy‐dispersive system (SEM–EDS, 63 samples analysed) and laser ablation – inductively coupled plasma – mass spectrometry (LA–ICP–MS, 41 samples analysed). Among the glass fragments analysed, dark brown, dark purple and dark green hues could be distinguished. Only among the dark green fragments could a clear compositional distinction be observed between fragments dated to the periods before and after ad 150. In the early samples (first century bc to first century ad ), iron, responsible for the green hue, was introduced by using impure sand containing relatively high amounts of Ti. In contrast, a Ti‐poor source of iron was employed, containing Sb, Co and Pb in trace quantities, in order to obtain the dark green colour in the later glass samples. The analytical results obtained by combining SEM–EDS and LA–ICP–MS are therefore consistent with a differentiation of glassmaking recipes, detectable in glass composition, occurring in the period around ad 150.     

NEUTRON ACTIVATION ANALYSIS OF SIXTEENTH- AND SEVENTEENTH-CENTURY EUROPEAN BLUE GLASS TRADE BEADS FROM THE EASTERN GREAT LAKES AREA OF NORTH AMERICA*

Sixteenth- and seventeenth-century European blue glass trade beads from aboriginal sites in the eastern Great Lakes area of North America have been analysed non-destructively using low neutron dose instrumental neutron activation analysis, so that the beads could be returned to their keepers. Dark blue (cobalt-coloured) beads are readily separable from turquoise (copper-coloured) beads. Differences in the chemistries of the turquoise blue beads appear to be useful in separating glass beads from the two centuries. Low calcium, sixteenth-century turquoise beads tend to distintegrate by a leaching of the alkali metals.     

THE USE OF TRACE ELEMENT ANALYSIS OF ENTRAPPED SLAG INCLUSIONS TO ESTABLISH ORE – BAR IRON LINKS: EXAMPLES FROM TWO GALLO‐ROMAN IRON‐MAKING SITES IN FRANCE (LES MARTYS,MONTAGNE NOIRE,AND LES FERRYS,LOIRET)*

Knowledge of the iron trade in ancient times rests on determining the source of the objects recovered during archaeological excavations. Unfortunately, attributing the origin is not always possible using archaeological tools alone. Trace element data of the ore and the archaeological material (reduction and reheating slags, entrapped slag inclusions from the bloom, bar iron and iron blades) from two Gallo‐Roman iron‐making centres, Les Martys (Montagne Noire) and Les Ferrys (Loiret), were determined using ICP–AES/MS and LA–ICP–MS. The results highlight a continuity of composition that makes it possible to establish a link between the initial ore and the semi‐finished iron products.     

SCANNING ELECTRON MICROSCOPY-ENERGY DISPERSIVE SPECTROMETRY AND PROTON INDUCED X-RAY EMISSION ANALYSES OF MEDIEVAL GLASS FROM KOROINEN (FINLAND)*

Thirteenth- to fourteenth-century ecclesiastical window glass, excavated from the administrative centre of Koroinen, Finland, represents the earliest window glass in the country and includes the only emerald green window glass known from Finland at this time. This was examined, together with some excavated vessel glass. X-ray analysis, using scanning electron microscopy-energy dispersive spectrometry and proton induced X-ray emission, reveals that while the vessels are made from potash-lime, soda-lime, mixed alkali and lead-silica glasses, the window glasses are lead-silica and wood ash-lead-silica glasses; they resemble similar glasses from central Europe and suggest that Koroinen shared the trading network of other European religious centres.     

THE BLUE ENAMELS IN THE BAROQUE DECORATIONS OF THE CHURCHES OF PALERMO,SICILY: FE2+‐COLOURED GLASSES FROM LIME KILNS*

Deep blue glasses coloured by octahedral Fe²⁺ cations are often reported as textbook examples of blue pigmentation. However, despite the possibility of laboratory synthesis under reducing conditions, to date there are no well‐reported occurrences of their production and use in the past. A thorough historical, ethnographic, mineralogical, and chemico‐physical investigation of the ‘smaltini di calcara’ from several baroque churches in Palermo, Sicily, has revealed that the blue enamels widely used for altar decorations in the 17th and 18th centuries are actually a unique case of ancient blue glasses pigmented by divalent iron cations in distorted octahedral coordination. This mixed‐alkali glass was accidentally produced under severely reducing conditions in the local kilns during production of lime.     

MINERALOGICAL INVESTIGATIONS OF MEDIEVAL BRICK SAMPLES FROM BÉKÉS COUNTY (SE HUNGARY)

Brick samples from nine archaeological sites representing seven contemporary medieval settlements in Békés County (SE Hungary) were analysed by quantitative X‐ray powder diffraction, optical microscopic, scanning electron microscopic and coupled thermal analytical – evolved gas analytical methods. The aims of this study were to give a mineralogical–petrographical characterization of the brick samples, to gain possible information on the raw clay and the admixed materials, and to determine the firing techniques applied in medieval southeastern Hungary. The mineralogical composition of the samples suggests that the locally extracted clay was mixed with fluvial sand and wheat (Triticum monococcum L.) chaff. The moulded bricks were fired in clamps. The different degrees of calcite consumption suggest that the firing temperature ranged from ～750°C to ～950°C. Moreover, the well‐developed reaction coronas on calcite grains indicate long firing times, lasting perhaps several days.     

ANALYSIS OF FIRST MILLENNIUM bc GLASS VESSELS AND BEADS FROM THE PICHVNARI NECROPOLIS,GEORGIA*

The Pichvnari necropolis on the Black Sea coast of Georgia lies in an area known in the late first millennium as ‘Colchis’, on part of the trade route leading to the Orient. The burials of the necropolis date to the late fifth century bc and frequently contain grave goods, including extremely well‐preserved polychrome glass beads and core‐formed vessels. This paper presents a study of these vessels both stylistically and archaeologically and using SEM–WDS and LA–ICPMS. It reveals that the vessels have compositional differences that may point to multiple manufacturing sites. One of the vessels appears stylistically unique and may exhibit one of the earliest uses of manganese as a decolorizer. Major and minor element data for the vessels suggest that they may belong to the same ‘Levantine’ group as many Roman glass objects, suggesting that a source of sand on the coast of the Levant could have been used in their production. The beads clearly show glass with both natron‐ and plant ash‐based flux with distinct rare earth compositions, showing multiple sites of production, some of which were probably either in the Middle East or the Indian subcontinent.     

THE SUPPLY OF CAMPANIAN‐MADE SIGILLATA TO THE CITY OF POMPEII

Pompeii is an important temporal reference in the study of Roman ceramics, yet until now the origins of red slip tableware or sigillata found in the city have largely been classified by visual evaluations of the pottery. This investigation employs petrographic and elemental analyses to establish the provenance of sigillata found in two pre–ad 79 contexts of Pompeii. In contrast to previous studies, the results suggest that pottery workshops in the vicinity of Somma‐Vesuvius played a vital role in the supply of sigillata to the city.     

The Supply of Glass at Portus Ilicitanus (Alicante,Spain): A Meta‐Analysis of HIMT Glasses

Portus Ilicitanus (Picola, Alicante) was the main sea harbour of the Roman Colonia Iulia Ilici Augusta and as such played a crucial role in the supply of fundamental commodities to the Iberian Peninsula. Excavations yielded large quantities of glass in fourth‐ and early fifth‐century contexts. Elemental analysis of 60 samples by laser ablation – inductively coupled plasma – mass spectrometry (LA–ICP–MS) confirmed that the glasses were imported from the Eastern Mediterranean. A majority of the glasses correspond to the HIMTa primary production group, which originates from Egypt. The statistical evaluation of published data of 589 HIMT glasses further revealed differential distribution patterns of the HIMTa and HIMTb subtypes between the Eastern and Western Mediterranean, suggesting chronological trends that are linked to wider geopolitical changes. This demonstrates the need for systematic large‐scale approaches to identify supply patterns and possible factors underlying geographical differences and/or chronological developments.     

CUERDA SECA CERAMICS FROM AL‐ANDALUS,ISLAMIC SPAIN AND PORTUGAL (10TH−12TH CENTURIES AD): INVESTIGATION WITH SEM–EDX AND CATHODOLUMINESCENCE*

Since little is known about the cuerda seca technique, our aim has been to complete an initial analysis of 11th‐century cuerda seca by studying fragments from the 10th century (Pechina, Almería) and the 12th century (Mértola and Almería), so as to establish the diachronic evolution of this technique. Characteristics specific to cuerda seca ceramic glazes were investigated using scanning electron microscopy (SEM) and quantitative chemical analysis with energy‐dispersive X‐ray spectrometry (EDX). The chemical compositions of the different‐coloured glazes (green, black, yellow and white) have given us valuable indications about the evolution of the technique. The opacification mode and the firing process were also investigated. With the help of cathodoluminescence (CL) and the study of modern ‘cuerda seca’ glazed ceramics, new hypotheses regarding the number of firing stages, taking into account glaze and paste transformations and their interactions, are put forward.