Non-destructive pXRF of mafic stone tools

Archaeological use of non-destructive pXRF has been most systematically applied to the classification and provenancing of volcanic glass (obsidian) artefacts. Comparable work has yet to be developed for non-vitreous artefacts. We report results of pXRF analysis for a sample of grey to black (mafic) aboriginal hatchets from Sydney and adjacent coastal regions to the north and south. The study shows both broad and detailed classification is achievable depending on rock type and degree of elemental depletion or enrichment of the samples. PXRF analysis reveals not only distinct patterns of resource use between the three regions of this study but also enables a high degree of geographic resolution in the case of the basalt artefacts of our sample. We conclude that non-destructive pXRF is effective for reliable characterisation of non-vitreous stone artefacts that have a sufficiently complex and enriched compositional signature (i.e., unaltered basalts); with ∼50% of the basalt hatchets in our sample matched with spatially and geologically specific sources.     

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.     

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.     

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.     

The Early Bronze Age settlement of Fidvár,Vráble (Slovakia): reconstructing prehistoric settlement patterns using portable XRF

This paper presents first results of chemical analyses of sediment samples from the Early Bronze Age (EBA) settlement Fidvár near Vráble (Slovakia). Large-scale geomagnetic prospection revealed detailed architectural remains of a fortified settlement. Other structures such as an earthwork of the linear pottery culture and at least two Roman march camps were found too. An Auger programme provided sediment samples of different depths, A) from an EBA house and the outer fortification ditch, B) from a potential metal workshop area as indicated by surface finds, and C) from an area located in the settlement's centre. The samples were analysed by a portable X-ray fluorescence (pXRF) spectrometer in order to investigate the vertical and horizontal distribution of chemical signatures. The comparison of geophysical data and three-dimensional chemical patterns gives us the opportunity to determine the human impact and to reconstruct activity patterns. The potentials and limits in the application of pXRF in archaeological soil chemical surveys are evaluated by systematic comparisons with high resolution laboratory measurements, including atomic absorption spectrometry (AAS) and inductively coupled plasma optical emission spectrometry (ICP-OES). The pXRF analyses can be reproduced well and show a good accuracy. Whilst (p)XRF analyses reflect the total composition of archaeological soil samples, the results of the AAS and ICP-OES analyses are fundamentally influenced by the acid digestion or extraction methods used. The pXRF analyses of the Vráble soils showed typical patterns of human occupation. For example, there are strong positive correlations between phosphorous, strontium and calcium. Phosphorous shows an enrichment in pathways and the fortification ditch. It is less strongly enriched within the sediments of house structures. Similar results apply to calcium and strontium distribution. But compared to the respective concentrations in sediment samples from the ditch they show a considerably higher variation in samples associated with house structures; that is, individual samples of sediments from house structures contained high concentrations of both, calcium and strontium. The deposits of an area that according to surface finds was thought to represent a potential metal workshop did not show indicative chemical signatures. Targeted excavations confirmed the absence of such as workshop. Finally it was shown that the refill history of the innermost fortification ditch (sample area D) and the overall cultural occupation sequence at the site correlate strongly with the chemical signatures of the respective ditch profile. The systematic variation of key elements along the profile opens up an entirely new perspective for interpreting the site's history. Overall, the study shows the great potential of pXRF as valuable part of an archaeological survey toolkit.     

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.     

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.     

pXRF method development for elemental analysis of archaeological soil

Portable X-ray fluorescence (pXRF) is now widely used for detecting the elemental composition of a material. Elemental analysis can enhance archaeological interpretations, such as mapping, preservation analysis and identifying anthropogenic activities. However, validated and reproducible protocols for analysing archaeological soil are still required. The elemental concentrations detected with three sets of preparation methods were compared: in-situ (no preparation), in-field (analysing through plastic bags) and ex-situ analysis (laboratory-based preparation). Influential factors were also investigated: calibration parameter, moisture, homogeneity, sieve size and soil type. In-field analysis attempted to improve reliability without offsite processing, but instead substantially reduced elemental concentrations and skewed the proportional distributions. Ex-situ analysis significantly increased elemental concentrations and reduced variation. Proportional distribution was different between the three methods, but unchanged following homogenizing and sieving. These comparisons demonstrated that ex-situ analysis maximizes detection and ensures consistent samples.     

Multivariate comparison of ICP-OES and PIXE/PIGE analysis of east Asian storage jars

In this paper we compare the results of proton-induced X-ray and gamma-ray emission (PIXE/PIGE) and simultaneous inductively coupled plasma–optical emission spectrometry (ICP-OES) using a multivariate modeling approach. Paired samples from 17th century east Asian stoneware jars recovered from dated shipwrecks provide the test population. The comparison highlights similar elemental behaviors irrespective of technique but shows that the additional elements available through ICP-OES provide identification of subgroups not evident in the PIXE/PIGE dataset. This study concludes that high dimensional datasets, such as those provided by ICP-OES, are preferable for modeling compositional groups where the archaeological samples are of unknown compositional range. It also highlights the power of multivariate approaches in assessing the quality of data generated by different techniques.     

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.     

Investigating ancient technology and ceramic composition at Al-Khidr site (Failaka Island,Kuwait): Geochemical analyses of Bronze Age pottery by pXRF and thin-section petrographic analyses

Pottery assemblages from the site of Al-Khidr on Failaka Island, Kuwait, were analysed in order to reconstruct the chemical composition of Bronze Age wares and to build a mineralogical database of Bronze Age pottery dated from Failaka Periods 1–3B (2000–1650 BCE). A total of 145 ceramic sherds from Al-Khidr, as well as reference groups, were analysed by non-destructive portable X-ray fluorescence (pXRF) spectrometry. Preliminarily petrographic thin-section analysis was applied to four samples to reconstruct possible clay paste recipes and to identify raw materials. The results indicate that geochemical analyses can successfully distinguish subgroups within a typological category of ceramic assemblages. The results identified two subgroups within the Al-Khidr typological category: the Dilmun Barbar tradition and the Mesopotamian tradition. Future comparative compositional studies can be conducted to explore other aspects of craft specialisation, such as ceramic technological choices and possibly the influence of sociopolitical units.     

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.     

New pieces: the acquisition and distribution of volcanic glass sources in northeast China during the Holocene

Little is known about the diversity of volcanic glass sources used in prehistoric northeast China. Although preliminary research established the presence of a number of sources in archaeological sites from this area, the exact location of these sources was not known (Jia et al., 2010). A recent geoarchaeological survey of three source areas and new data derived from portable X-ray Fluorescence elemental analysis (pXRF) has revealed not only the location and use of two new geological sources in northeast China but also extended our understanding of the geologic context of volcanic glass from Tianchi/Paektusan Volcano, the major geological source of volcanic glass in northeast China. Furthermore, understanding the geological history of these new sources clarifies why they were only found in archaeological sites dated to the Holocene.     

Pigment analysis in Bronze Age Aegean and Eastern Mediterranean painted plaster by laser-induced breakdown spectroscopy (LIBS)

Laser-Induced Breakdown Spectroscopy (LIBS) was used in the examination of Bronze Age painted plaster samples from several sites in the Aegean and Eastern Mediterranean. The elemental content of paint materials was determined in most cases leading to the identification of the pigment used in agreement with data from analyses of the same samples with other established techniques. The analyses demonstrate that a virtually non-destructive technique such as LIBS provides sufficient data for the elemental characterisation of painting materials while in parallel has the capability for routine, rapid analysis of archaeological objects enabling the quick characterisation or screening of different types of artefacts. This certainly shows an important way forward in technological studies of fragile and scarce archaeological material.     

Innovative application of portable X-ray fluorescence (XRF) to identify Göktepe white marble artifacts

An efficient and non-destructive method to classify white marble artifacts by using a hand-held, portable XRF analyzer (pXRF) is here reported. The identification is based on the uniquely high strontium content of this marble and has been verified by testing 32 artifacts, most of which had already been provenanced, using conventional micro-destructive analyses. Besides strontium, other potential provenance indicators, such as manganese and iron, were analyzed and their concentration values obtained after empirical calibration of the instrument by using 17 quarry samples of known composition. The results show that Göktepe/non-Göktepe discrimination is almost always possible (30 artifacts) and that additional analyses are required only when the Sr value is at the lower edge of the Göktepe field (2 artifacts). The success of the method, however, resides in the particular composition relative to trace elements of Göktepe and is not easily extended to other marble varieties. Main reasons are related to insufficient accuracy at low concentration values, intrinsic trace variability of marble artifacts, surface effects that may produce not representative results. Interest in the method therefore is tightly linked to the exceptional importance of Göktepe as a sculptural marble, in which case, detailed data, obtained with a fast and totally non-destructive method, may provide relevant information concerning chronology, workshops, and places of production of the artifacts.     

Quantitative EDXRF Studies of Obsidian Sources in Northern Hokkaido

Quantitative trace element data from six obsidian sources on the Japanese island of Hokkaido is presented. Previous work by Japanese scholars has utilized neutron activation analysis (NAA) focusing on the rare earth elements, or qualitative energy dispersive X-ray fluorescence (EDXRF). In this study, non-destructive EDXRF is used to generate trace element data for 9 elements. Bivariate plots of the incompatible trace elements (Ba, Rb, Sr, Y, and Zr) can be used to separate the obsidian sources in this study. Source separation was confirmed by using linear discriminant analysis. Stepwise discriminant analysis indicates that Ba, Sr, Rb, Ti, Y, and Zr are the most discriminating elements.     

Reassessing the northern limit of maize consumption in North America: stable isotope,plant microfossil,and trace element content of carbonized food residue

In combination, the analysis of carbonized food residue for stable C and N isotopes, elemental composition, and plant microfossils (phytoliths and starch granules) offers a powerful tool for understanding patterns of prehistoric maize (Zea mays) consumption in small-scale societies. Using this approach, we conclude that maize was more widely consumed in North America than previously suspected. Between ∼AD 700 and 1600, despite little or no archaeological evidence of gardening, corn was a widespread component of diet on the eastern Canadian prairies. This pattern, furthermore, extended into the adjacent boreal forest at about the same time. However, carbon (δ¹³C) and nitrogen (δ¹⁵N) values on food residue samples vary widely, suggesting significant overall dietary differences from one region to the next. Analysis of a subset of residue samples for elemental composition (using ICP-OES [inductively coupled plasma–optical emission spectrometry]) may help identify broad trends in the provenience of foods consumed at these sites.     

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.     

Geochemical Methods for Sourcing Lava Paving Stones from the Roman Roads of Central Italy

This paper documents the results of in situ analysis of 306 lava paving stones and 74 possible source rocks using pXRF. Data were collected from sites both in the city of Rome—on major roads beyond the city (including the Viae Flaminia, Cassia, Clodia, Praenestina and Appia)—and in the city of Ostia. Comparison of the pXRF data with lava compositional data from the geological literature allows broad identification of possible sources. The results point to quite distinctive patterns of exploitation for the city of Rome and Ostia, utilizing the Alban Hills lava flows, and the roads of the middle Tiber Valley, drawing on lava flows associated with the Vico and Sabatini volcanoes. The results show the potential of pXRF to produce data to elucidate the exploitation of lava flows for paving the Roman roads.     

Portable XRF analysis of zoomorphic figurines, “tokens,” and sling bullets from Chogha Gavaneh,Iran

This study examines small finds from the site of Chogha Gavaneh, Iran, including zoomorphic clay figurines, geometric-shaped objects (often referred to as “tokens”), and sling bullets in order to investigate the possible social and economic functions of these artifacts. While Chogha Gavaneh has been occupied from the Pre-Pottery Neolithic A (PPNA) (ca. 9000 B.C.E) period to the present, we focus on 87 small finds from the Early Chalcolithic period (ca. 5000–4000 B.C.E.). We explore how portable X-ray fluorescence spectrometry (pXRF) provides a new line of data with which to test the conventional wisdom about the uses of these small finds. Our findings suggest that local production is unlikely to account for the diversity in the elemental composition of the small finds. We argue that this supports claims that Neolithic and Chalcolithic people exchanged “tokens”. The presence of non-local zoomorphic figurines also raises interesting questions regarding their possible role in past societies.