Non-destructive PXRF analysis of museum-curated obsidian from the Near East

Non-destructive pXRF has the potential to expand sample populations of archaeological provenancing studies by facilitating access to museum collections of artefacts. In this study, we use museum-curated obsidian for the sites of Tell Brak, Mersin-Yümüktepe and Tell Arpachiyah and geological obsidian samples from central Turkey to demonstrate that non-destructive pXRF is comparable to other techniques in differentiating between Near Eastern obsidian sources. Secondly, we use multivariate analysis to evaluate whether non-destructive pXRF is sufficiently accurate and precise to enable comparison with legacy datasets from previous analysis using PIXE and ICP-MS. Multivariate analyses show that instrumental offsets between the results from pXRF and other analytic techniques are less than source-to-source variation typical for most Anatolian obsidian outcrops and pXRF-identified geochemical groups are directly comparable to legacy datasets. Non-destructive pXRF analysis indicates that during the Chalcolithic, East Göllü da? and Nenezi da? continued to be the major sources of obsidian to communities in central Anatolia and the Bingöl range and mountains surrounding Lake Van supplied sites east of the Levant. Variations in the analysed assemblages suggest a number of obsidian exchange networks existed during this period.     

Geochemical characterisation of north Asian glazed stonewares: a comparative analysis of NAA,ICP-OES and non-destructive pXRF

The analytical performance of non-destructive portable X-ray fluorescence (pXRF) is compared with that of Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) and Neutron Activation Analysis (NAA) for the elemental characterisation of a group of glazed stonewares from North-East Asia. As a non-destructive technique pXRF is potentially well suited to the elemental analysis of high value archaeological and museum collections but has yet to be critically evaluated for the analysis of archaeological stonewares. In this study we use multivariate evaluation to compare results from non-destructive pXRF in relation to ICP-OES and NAA analysis for the same group of samples. We conclude that, although pXRF is comparatively limited to a small number of major, minor and trace elements, these are sufficient to identify the same compositional groups as high dimensional ICP-OES and NAA datasets for this assemblage.     

A characterisation study of Ubaid period ceramics from As-Sabbiya,Kuwait, using a non-destructive portable X-Ray fluorescence (pXRF) spectrometer and petrographic analyses

The Ubaid cultural phenomena (6500–4200 BC) of southern Mesopotamia has been used to characterise other archaeological sites in the Arabian Gulf region. The aim of this inquiry is to explore the nature of the interaction between the homeland of the Ubaid and the wider Gulf region. Through the use of a non-destructive portable X-ray fluorescence (pXRF) spectrometer, this study seeks to characterise and identify the chemical and mineralogical compositions of the ceramic assemblage from the Bahra 1 site of the As-Sabbiya region, Kuwait. The chemical results demonstrated that a combination of six trace elements [rubidium (Rb), strontium (Sr), yttrium (Y), zirconium (Zr), niobium (Nb) and barium (Ba)] occur significantly enough to delineate clay-based artifact groups—local red coarse from Ubaid, while the mineralogical analysis confirms the pXRF result and identifies the source of the raw materials and temper as well. Also, the comparison between the Ubaid and Bronze Age assemblage results suggests that potters used different clay resources within their own regions and/or production techniques.     

Non-destructive provenance study of cuneiform tablets using portable X-ray fluorescence (pXRF)

Portable X-Ray Fluorescence (pXRF) apparatus of the last generation was tested to determine its potential for routine provenance determination of clay cuneiform tablets, which cannot be analyzed by “classical” intrusive methods. A group of tablets from Hattuša (Bo?azköy) and from el Amarna, which were previously provenanced using optical mineralogy (OM) and instrumental neutron activation analysis (INAA), was analyzed by pXRF and the results were used to establish the grouping according to their elemental concentrations. These groups were compared with the previous results retrieved by OM and INAA in order to confirm their validity. The results corroborate the high potential of the pXRF for non-destructive study of well-defined, ‘closed’ assemblages of clay-derived, delicate artifacts, such as cuneiform tablets, bullae, and fine-ware pottery. Consequently, a group of previously unexamined tablets from Hattuša was analyzed by pXRF and the results are discussed with implications on future research.     

Parameters in the use of pXRF for archaeological site prospection: a case study at the Reaume Fort Site,Central Minnesota

Field portable/hand-held x-ray fluorescence (pXRF) analyzers have been characterized as potentially useful for archaeological site prospection, but little has been published on the parameters of their use in this manner. The purpose of this study is to explore whether the variability of surface geochemistry as characterized with a pXRF analyzer corresponds with subsurface archaeological features at a site subsequently excavated, and what conditions influence the success of this endeavor, including feature depths, soil moisture, and sample processing. A 520 m² within-site area was systematically surveyed on a 2 m interval, within which several types of archaeological features were excavated (chimney bases, wall trenches, and a bonebed of faunal waste), taking readings in situ and collecting samples for ex situ testing (undried, dried but not powdered, and dried/powdered). The four different tests of each grid location, analyzed through univariate and multivariate tests, showed that the pXRF surface data does correspond with some types of subsurface features when those features are very shallow (within 5 cm of surface level) and are associated with clayey fills. Further, the data from the subsurface samples provides excellent distinction of feature fills from other sediments, regardless of sample preparation. In situ surface survey with pXRF analyzers may however be adequate for sites with a thorough baseline geochemical database.     

An atypical Ancient Egyptian pillow from Sedment el-Gebel: evidence for migrant worker trading and technology

Archaeological artefacts are irreplaceable information resources. Consequently analytical methods must be non-destructive or use the minimum of sample so that an artefact remains accessible and unchanged for future research. The significance and innovation of the current study is the application of micro- and non-destructive analytical methods to an ancient Egyptian pillow in order to gain new knowledge about funerary customs, population composition, trade routes, and technological expertise. In this study, the analytical results highlight the funerary customs of a migrant community within ancient Egypt with an ephemeral technological expertise.     

pXRF: a study of inter-instrument performance

Integrating portable X-ray fluorescence (pXRF) instrumentation into archaeological investigations has generated as much interest as skepticism because several characteristics of the technique limit analytical accuracy and precision. This paper seeks to explore inter-instrument performance in order to assess the potential pXRF instrumentation has in examining the elemental composition of lithic raw materials. Two pXRF instruments, Delta and Omega models both manufactured by Olympus Innov-X Systems, were utilized to obtain the trace element signatures of five fine-grained volcanic sources and four obsidian sources in the Great Basin. We compared the two portable instruments to a wavelength-dispersive instrument extensively calibrated with geologic standards and to a commercial benchtop energy-dispersive system. Our results suggest that the relationships between the data produced by these different instruments are complex, and as we look to the future of pXRF use in archaeological analysis we argue that that the same strict protocols applied in laboratory-based XRF analyses, involving instrument calibration, evaluation of inter-instrument performance, and comparison to accepted geologic standards, need to be applied in pXRF analysis.     

Characterization of New Zealand obsidian using PXRF

New Zealand has some of the most active areas of rhyolitic volcanism in the world and this has produced numerous obsidian sources in the northern half of the North Island. In total archaeologists have recognized 27 named locations from which obsidian can be obtained scattered across 4 geological source regions. Shortly after colonization in the late 13th century AD Polynesian settlers began transporting this material some thousands of kilometers throughout the country and across the sea in small quantities to distant neighbors in the Kermadecs and Chatham islands. Although considerable research has been conducted on obsidian sourcing in New Zealand the complexity of geochemical source discrimination and the lack of a practical method of non-destructive geochemical analysis has hindered progress. We present the results of our use of PXRF to provide geochemical data on New Zealand obsidian sources and to compare the use of discriminant analysis and classification tree analysis to discriminate among sources and attribute archaeological samples to sources. Our research suggests that classification tree analysis is superior to discriminant analysis in sourcing studies. A large case study using an important settlement phase site (S11/20) from the Auckland region demonstrates the utility of the methods and the results support a model of high degrees of mobility and interaction during the early settlement of New Zealand.     

Non‐Destructive Survey of Early Roman Copper‐Alloy Brooches using Portable X‐ray Fluorescence Spectrometry

This paper argues that portable X‐ray fluorescence spectrometry (pXRF) is a suitable elemental measurement technique to study the production of copper‐alloy artefacts. However, rather than try to imitate the accuracy and precision of laboratory techniques, it is more beneficial to deploy it in a survey role, one that attempts to model chronological and geographical changes within large quantities of artefacts. To achieve this, it was investigated to what extent corrosion and the issues surrounding surface measurements affect the potential of this type of research. Analyses on early Roman period brooches gathered in the Nijmegen region of the Netherlands were subsequently compared with published data.     

The technological versus methodological revolution of portable XRF in archaeology

Portable X-ray fluorescence (pXRF) instruments have gained considerable attention within the archaeological community. Few other recent instrumental developments have generated such debate. Much of this debate, which is dominated by scepticism over analytical performance, has occurred in informal settings. Rather than judge the use of pXRF based on unpublished work and conference banter, we conducted an extensive literature review of peer-reviewed research that used this technology. Our focus is developing an understanding of how, where, and why pXRF is being used in archaeology. What interests us most are research designs into which only pXRF could be integrated and the new research approaches these instruments may facilitate. Trends that emerged from the literature are surprising. For example, only 43% of the archaeological “pXRF” papers actually involve handheld instruments. In addition, more than four-fifths of handheld pXRF in archaeology is apparently conducted in laboratory contexts. Only 3% has been conducted in a fieldhouse or on-site laboratory, and 15% at an excavation, on a survey, or inside a historic structure. Here we argue that, while the technical capability to analyse archaeological materials using portable instruments may exist, it is not necessarily true the methodological and theoretical frameworks are in place to allow such activities to be archaeologically successful and significant. Because handheld pXRF is uniquely suited to in situ analysis, we expect the first changes in methodological and theoretical approaches will involve space, context, and related frameworks.     

X-ray and neutron-based non-invasive analysis of prehistoric stone artefacts: a contribution to understand mobility and interaction networks

Carbonate-rich archaeological artefacts are difficult to identify and correlate between them and with raw materials of such heterogeneous geological sources, especially when only non-invasive analysis is possible. A novel combination of X-ray and neutron-based non-invasive analysis is implemented and used for the first time to study prehistoric stone idols and vessels, contributing to culture identity, mobility and interaction in the recent Prehistory of Southern Iberia. Elemental composition was obtained by prompt gamma activation analysis (PGAA) and external beam particle-induced x-ray emission (PIXE); homogeneity of the stone artefacts and the presence/absence of internal fractures were obtained by neutron radiography (NR). These atomic and nuclear techniques, simultaneously used for complementary chemical information, have been demonstrated to be of great value as they provide non-destructive compositional information avoiding sample preparation, crucial in so singular and rare objects. The obtained results, especially of PGAA, are very promising and useful in general assessments of provenance. The stone artefacts show signs of both nearby and long-distance procurement, as well as of unknown attribution.     

ANALYSING ARCHAEOLOGICAL BASALT USING NON‐DESTRUCTIVE ENERGY‐DISPERSIVE X‐RAY FLUORESCENCE (EDXRF): EFFECTS OF POST‐DEPOSITIONAL CHEMICAL WEATHERING AND SAMPLE SIZE ON ANALYTICAL PRECISION*

Energy‐dispersive X‐ray fluorescence (EDXRF) has been commonly used to determine geological sources of volcanic glass artefacts, but its ability to discriminate between basaltic sources is less developed. We examine the precision and accuracy of non‐destructive EDXRF for basalt artefacts by analysing varying size and weathering characteristics. The experiments identified no appreciable effect in reproducibility or measured composition due to thickness (down to 1 mm) or natural weathering of pre‐contact flake scars for the 17 elements measured in this study. Samples with surface area less than 100 mm², however, show significant variability in measured composition and reproducibility.     

江阴高城墩遗址出土良渚文化玉器的无损分析研究

为判断江阴高城墩遗址出土良渚文化玉器的地质成因和产地,利用外束质子激发X荧光技术(PIXE)、X射线衍射(XRD)、激光拉曼光谱(LRS)等无损分析技术对出土玉器进行了化学成分、矿物学特征分析。实验结果显示,46件玉器中67.4%的样品主要矿物组成为透闪石,玉料的质量较好,可能来自同一种成矿类型的矿床。研究表明无损伤分析技术是古代玉器研究的有效手段。研究结果为探索良渚文化遗址出土玉器的玉料来源提供了科学证据。     

Non-invasive characterization through X-ray fluorescence and neutron radiography of an ancient Japanese lacquer

Oriental lacquer artefacts represent very interesting objects of investigation, involving a huge variety of materials and manufacturing techniques. Lacquers are very attractive not only for their stylistic features but also for understanding the variety of production processes, time evolution, use and artistic applications involved in their manufacturing. Till recently, the research activity on these materials has been mainly based on standard, more or less invasive, analytical methods. With the aim to characterise a nineteenth century Japanese lacquer in a totally non-invasive and non-destructive way, in situ X-ray fluorescence (XRF) and neutron radiography (NR) have been employed. While XRF suggested an identification of the pigments embedded into superficial layers, NR allowed revealing, in a single measurement, the average bulk properties of the sample.     

A novel and non-destructive approach for ZooMS analysis: ammonium bicarbonate buffer extraction

Bone collagen is found throughout most of the archaeological record. Under experimental conditions, collagen is apparently preserved as an intact molecule, with amino acid compositions and isotopic profiles only changing when almost all of the protein is lost. The ubiquity of collagen in archaeological bone has lead to the development of the use of collagen peptide mass fingerprints for the identification of bone fragments—Zooarchaeology by Mass Spectrometry (ZooMS). We report a novel, but a simple method for the partial extraction of collagen for ZooMS that uses ammonium bicarbonate buffer but avoids demineralisation. We compared conventional acid demineralisation with ammonium bicarbonate buffer extraction to test ZooMS in a range of modern and archaeological bone samples. The sensitivity of the current generation of mass spectrometers is high enough for the non-destructive buffer method to extract sufficient collagen for ZooMS. We envisage that a particular advantage of this method is that it leaves worked bone artefacts effectively undamaged post-treatment, suitable for subsequent analysis or museum storage or display. Furthermore, it may have potential as a screening tool to aid curators in the selection of material for more advanced molecular analysis—such as DNA sequencing.     

REPRODUCIBILITY OF ELEMENTAL ANALYSES OF BASALTIC STONE ARTEFACTS BY QUADRUPLE ICP–MS USING DIFFERENT SAMPLE SIZES AND DIGESTION METHODS,WITH IMPLICATIONS FOR ARCHAEOLOGICAL RESEARCH

Using high‐precision inductively coupled plasma mass spectrometry (ICP–MS), we measured >40 elements in basalts sampled by diamond micro‐drills to evaluate the effectiveness of different digestion methods and the reproducibility of elemental analysis for different sample sizes from 5 mg to 100 mg. The results indicate that those elements that are most suitable for geochemical characterization, such as rare earth elements (REE), high‐field strength elements (HFSE) and certain mobile elements (Rb, Sr, Th, U), show excellent reproducibility with an average relative standard deviation (RSD) of 3% between open‐beaker and pressured ‘bomb’ digestion methods. This observation rules out the presence of refractory phases such as zircon, which can only dissolve in pressured ‘bombs’, and suggests that the results from open‐beaker digestion are reliable. The ICP–MS data for powders of different weights ranging from 10 to 100 mg collected from two fine‐grained basalt artefacts display excellent reproducibility, with a RSD of <5% for the most important elements. The reproducibility is reduced when including the 5 mg weight fraction (RSD of ～2–9%), which is still sufficient for archaeological applications. Our results demonstrate the usefulness of 10 mg samples for elemental measurement, which is valuable for geochemical characterization and sourcing of fine‐grained basalt artefacts from museum collections that require minimal destructive sampling.     

A long-distance copper alloy trade to the North Eastern Baltic during the late pre-Roman and Roman Iron Age (250 BCE–450 CE) explored with lead isotope MC-ICP-MS

The North Eastern Baltic has no copper resources of its own, meaning that Cu alloy was imported either as raw material or as finished objects. The north-eastern coastline of Estonia during the late pre-Roman and Roman Iron Age was connected to the south by sea to the long-distance ‘amber’ trade route and to the east by Russian river systems. This study quantitatively assesses the direction of the Cu alloy supply in the region before and after brass enters circulation at the beginning of the Roman Iron Age. After an initial portable X-ray fluorescence (pXRF) survey, 18 objects were chosen for Pb isotope analysis. This isotope analysis resolved a group of nine brass artefacts from the Roman Iron Age amongst a ‘melting pot’ of other Cu alloys. The similarity between the isotope ratios found in the Roman world suggests the presence of the same ‘melting pot’ in the North Eastern Baltic, possibly created by a large amount of Roman Cu alloy being traded north. No evidence for Cu alloy from Scandinavia or the Ural Mountains could be found. The hypothesis from this small study is that the Cu alloy entering Estonia was dominated by metal from Southern Europe from the late pre-Roman Iron Age and the Roman period.     

ARAMAIC BASALT STATUES FROM TELL HALAF,SYRIA: LOCATING THE ANCIENT QUARRIES

Tell Halaf is the locality of the ancient Aramaic city of Guzāna (c. 1000–800 bc ) in Syria. The statues of Tell Halaf were made from monolithic basalt blocks, comprising massive as well as amygdaloidal types. However, the exact location of the original quarries was as yet unknown. Reconnaissance mapping and sampling concentrated on the four basaltic centres in the vicinity of Tell Halaf, covering both south‐eastern Turkey and north‐eastern Syria. In addition, basaltic artefacts from the two archaeological sites of Tell Beydar (c. 2700–2300 bc ) and Djebelet el Beda (c. 2600–2350 bc ) were investigated. All basalt samples were analysed for their bulk rock major and trace element compositions by X‐ray fluorescence, ICP–MS analysis and the mineral chemistry of individual minerals by combined electron microprobe analysis and laser‐ablation ICP–MS. The data show that basalt works of art from all three archaeological sites were derived from the Syrian basalt plateau of Ard esh‐Sheikh, approximately 57 km south of Tell Halaf. Accordingly, this basalt quarry was actively exploited over a considerable time span of c. 1900 years. This study demonstrates that petrographic and geochemical investigations of basalt, combined with electron microprobe and laser‐ablation ICP–MS analysis of minerals, are powerful tools to discriminate between possible sources of raw materials, especially if isotopic data yield unsatisfying results.     

NO STONE UNBURNED: A COMPOSITIONAL ANALYSIS OF OBSIDIAN MICRODEBITAGE BY LASER ABLATION TOF–ICP–MS

Obsidian is an effective material for the study of prehistoric raw material use and exchange, due to the high degree of homogeneity and redundancy of obsidian materials and manufactured objects in the archaeological record. The destructive nature of many analytical techniques often impedes compositional research because of the damage that may occur to priceless archaeological artefacts. The combination of time‐of‐flight (TOF) ICP–MS with a laser ablation sample introduction system provides a highly efficient means of chemically characterizing obsidian. This study shows that sample size limit capabilities of TOF–ICP–MS analysis of obsidian can reach less than 100 μm. Sampling and analysis of microartefacts enables researchers to overcome problems of sampling bias with very little damage to the valuable existing materials within the archaeological record and expands the potential for chemical compositional analyses in archaeology.     

CHARACTERIZATION OF ARCHAEOLOGICAL AND IN SITU SCOTTISH WINDOW GLASS

Scottish window glass from both archaeological sites and historic buildings was examined using portable X‐ray fluorescence (pXRF) and scanning electron microscopy – energy‐dispersive X‐ray micro‐analysis (SEM–EDX). The elemental composition of the glass provides information regarding the materials used and, subsequently, an approximate range of dates of manufacture. pXRF is shown to be more vulnerable than SEM–EDX to the effects of surface corrosion and matrix effects in archaeological samples. The study showed that the production of window glass in Scotland from the 17th century onwards appears to closely parallel that in England. It also demonstrated the potential of pXRF for in situ studies of window glass in historic buildings. pXRF was used to assess two Scottish buildings; one in state care and one in private ownership. The building in state care, the Abbot's House at Arbroath Abbey, showed a uniform glass type, suggesting that the building was re‐glazed completely at some point during the late 19th or early 20th century. The building in private ownership, Traquair House, had a range of glass types and ages, demonstrating a different maintenance and repair regime. This type of data can be useful in understanding historic buildings in the future, particularly if re‐glazing is being considered.