X-RAY FLUORESCENCE AND DENSITY MEASUREMENTS ON SURFACE-TREATED ROMAN SILVER COINS*

Some 630 Roman silver coins excavated at Augusta Raurica (Switzerland) have been analysed by non-destructive X-ray fluorescence and X-ray diffraction. Furthermore, the density and the weight have been determined. The measured average density of plated and massive depletion-silvered coins is lower than the density calculated from the chemical composition, whereas massive coins display equal values for both of the densities. Based on experimental X-ray investigations of modern silver (tempering, acid treatment, production of corrosion layers), the nature of corrosion products on silver, their impact on surface analysis, and aspects of wearing-off by circulation are briefly discussed.     

NON-DESTRUCTIVE RADIOISOTOPE X-RAY FLUORESCENCE ANALYSIS OF OLD SILVER COINS

The paper presents the results of a feasibility study of the application of X-ray fluorescence analysis to nondestructive analysis of coins. Radioisotope sources ⁵⁵Fe, ²⁴¹Am, ¹⁰⁹Cd and ²³⁸Pu were used for excitation and a Si/Li detector with a multichannel analyser for the measurement of characteristic X-ray lines. Silver and copper in Polish renaissance coins have been analysed. Analysis using Ag K and Ag L lines allows one to distinguish between blanched and unblanched coins. The accuracy of the silver determination using Ag K X-rays is claimed to be ± 0.5% Ag for homogenous coins and ± 1.0% Ag for blanched but well-preserved uncorroded coins.     

COMPARISON OF METHODS OF ANALYSIS OF SILVER AND GOLD IN SILVER COINS

A series of silver coins was analysed for silver and gold contents by three methods—chemical wet analysis, activation analysis and X-ray fluorescence using a point source linear spectrometer (milliprobe). The results indicate that while the X-ray fluorescence technique gives better agreement with chemical analysis for major components the use of activation analysis with automated equipment results in a considerable saving of time and has a high sensitivity for some minor components.     

Average and core silver content of ancient-debased coins via neutron diffraction and specific gravity

The measurement of the fineness of debased ancient silver coins has proven to be a very difficult issue, which has been studied for a long time. In this paper, this subject is analysed, and the various consequences of the silver surface enrichment (SSE) are discussed exploiting the most recent investigations. A new model is proposed for the complex object that is an ancient-debased silver coin, based on the silver profiles measured on some sectioned specimens. The model is applied to a sample of 43 coins, mainly Roman victoriati, Cisalpine and Illyrian drachms (from late III to I century B.C.). The coins are investigated in two different ways: neutron diffraction (ND) and specific gravity (SG). The results of the two measurements are combined via the proposed model to provide a more complete numismatic information of the original fineness of the monetary alloy. As a result, a relation between SSE thickness and SG is derived, which, for these coinages, allows to estimate the original alloy silver content from a simple SG measurement; the same method can be used to study other debased coinages, provided that all the procedure (ND and SG) is applied.     

ANALYSIS OF THE NOTCHES OF ANCIENT SERRATED DENARS*

A number of serrated silver denars of the Roman Republic and a Greek bronze coin were investigated, paying special attention to the notches, in order to reveal their production technique. Particular interest was devoted to three contemporary forgeries of serrated denars, because the official pure silver issues were also available for inspection. Several microbeam analytical techniques were applied, such as scanning electron microscopy (SEM), electron probe micro‐analysis (EPMA) and secondary ion mass spectrometry (SIMS). The surfaces of the notches, which show traces of the tools used, were investigated by SEM. In the case of the forged coins, the thickness of the silver layer (inside the notches as well as on the surface of the coin) was determined by SEM and SIMS. The main components of the surfaces were similar in both cases as measured by EPMA. Combining the results, it is possible to reconstruct the steps in the production of the serrated denars. The investigations also permit a review of different opinions about the purpose of the notches.     

AN ANALYSIS OF SOME THIRD-CENTURY ROMAN COINS FOR SURFACE SILVERING AND SILVER PERCENTAGE OF THEIR ALLOY CONTENT

The silver content within the body and at the surface of 22 Roman ‘bronze’coins dating to a.d. 274–305 was determined by X-ray fluorescence to discover whether these coins were silver dipped and/or issued with a deliberately added amount of silver in their alloy. Results of this analysis indicate that antoniniani and fractional coins of the period 274–294 were probably both silver dipped and minted in an argentiferous alloy. Radiate and laureate fractions issued after 295 do not seem to have had an argentiferous alloy, nor does this analysis provide any evidence that they were silverdipped.     

NEUTRON ACTIVATION ANALYSIS OF ANCIENT BURMESE SILVER COINS WITH A LOW FLUX AMERICIUM/BERYLLIUM NEUTRON SOURCE

Nondestructive neutron activation analysis is by now a well-established technique for the analysis of ancient silver coins. The high activation cross-section of silver for thermal neutrons makes it possible to also use this method with the low neutron fluxes available from an isotopic neutron source. In this case due consideration must be given to minimize the self-shielding effect which is encountered with coins above a few tenths of a millimetre thickness. A simple method for the determination of the silver, copper and gold content in silver coins based on the self-shielding properties of silver alloys of different fineness is described. The method has been found to be useful for the quick routine assay of silver coins for the purpose of their classification. Seventeen ancient Burmese silver coins from three different cultural periods of Burma, and two British coins for comparison have been analyzed by this method.     

ROME AND THE EAST. PRODUCTION OF ROMAN PROVINCIAL SILVER COINAGE FOR CAESAREA IN CAPPADOCIA UNDER VESPASIAN, AD 69–79

During the first three centuries AD several eastern provinces of the Roman empire produced silver coinages of specifically local denominations and types. It has been claimed that at certain periods the mint of Rome was employed to strike some of these coinages, rather than the provincial mints to which the coins are traditionally attributed. This claim is based mainly on stylistic observations, but because style is regarded as subjective, some other form of evidence to support these observations is desirable. In this paper three types of coin are submitted to metallurgical analysis: silver denarii struck at Rome; Roman-style provincial silver coinage; and 'local'style provincial silver coinage. The aim is to discover whether the Rome-style and 'local'style coins have different trace element profiles, and whether these might indicate different ore sources or refining techniques. The results are then compared with Roman denarii to see whether there are any similarities between the denarii and the Rome-style provincial silver coins.     

Determination of the Fineness of Medieval Coins—Evaluation of Methods in a Case Study of a Medieval Pfennig

The original fineness of coins is very important information that can help us to understand the commercial situation in a wide historical context. This paper deals with a comparison of analytical methods suitable for the evaluation of the actual and original fineness of coins based on a detailed case study of a medieval coin sample. Both non‐destructive (i.e., scanning electron microscopy/energy‐dispersive X‐ray spectroscopy, X‐ray fluorescence, atomic force microscopy and hydrostatic weighing) and destructive (i.e., inductively coupled plasma – mass spectrometry and the Volhard titration method) techniques were used. The original fineness can be also deduced from knowledge of the internal structure of the coin (limited miscibility of copper and silver). A new analytical method based on a combination of a micrograph of the metallographic cross‐section with consequent image analysis was developed for determination of the original fineness. The proposed approach is relatively simple and provides reliable values. Sample heterogeneity and its impact on the determination of fineness are also discussed.     

The coinage of ancient Hadramawt The Pre-Islamic coins in the al-Mukallâ Museum

The pre-Islamic coins in the al-Mukallâ Museum come principally from Shabwa, the capital of the kingdom of Hadramawt. The collection consists of 76 coins, three of which could not be identified because of their poor condition. Sixty-seven silver and bronze Hadrami coins; five silver and bronze Himyarite and Sabaean coins; and one gold Roman coin comprise the collection. This material provides a general overview of the coinage of the ancient Hadramawt, permitting us to distinguish the issues of certain individual Hadrami rulers.     

A Trial PIXE/PIGME analysis of Pre-Islamic Arabian Coinage

Eight previously published (1) pre-Islamic coins minted in Arabia were subjected to non-destructive ion beam analysis by Proton Induced X-Ray (PIXE) and Gamma-Ray Emission (PIGME) at Lucas Heights. The results (2) were interpreted using Principal Components Analysis (PCA). The relative X-ray intensities of fifteen elements, supplemented with additional L alpha lines for two of the elements, were extracted for this analysis. PCA (results appended) was first carried out on the whole dataset where the distinctive high iron and nickel composition of two coins (331 and 335) resulted in their position as outliers. A second analysis of the subset of silver coins showed the compositional similarity between four coins (44, 222, 226, 359) and distinguished two separate outliers. One of these (369) has a high lead and tin content while the other (354) has a greater proportion of elements present as impurities (?) including iron and nickel. The two outliers and the relatively homogenous compositions of the group of four coins suggest that three compositional types of silver coinage are represented in the dataset: 1. a relatively silver-rich group of four coins; 2. silver coins debased with lead; and 3. silver coins debased with iron and nickel.     

QUANTITATIVE ANALYSIS OF COPPER-TIN BRONZES BY MEANS OF GLOW DISCHARGE OPTICAL EMISSION SPECTROMETRY

Glow discharge optical emission spectrometry (GDOES) has been used for obtaining calibration curves for copper, tin, lead, silver, antimony, arsenic, zinc and iron from standards including copper-base alloys (Cu 61.33-99.95%) and from bronze Punic coins. The GDOES results were calibrated using atomic absorption spectroscopy with inductively coupled plasma atomization (ICPAAS) to analyse the standards and coins. For all these materials, the results show that via GDOES it is possible to obtain reliable and reproducible calibration curves for copper, tin, lead, zinc and iron with a linear behaviour as a function of the content. The quantitative GDOES and ICPAAS data for the coins have been also compared with those obtained via X-ray fluorescence (XRF) and it is shown that GDOES, ICPAAS and XRF agree well with one another considering that the bronze coins are inhomogeneous to some degree. As an example of GDOES analytical features, a depth concentration profile through a thin bronze patina is shown and briefly discussed.     

FINGERPRINTING OF ROMAN MINTS USING LASER‐ABLATION MC–ICP–MS LEAD ISOTOPE ANALYSIS*

In this paper we present data to demonstrate the applicability of laser‐ablation MC–ICP–MS isotope analysis to archaeological artefacts, in this case Roman silver coins. The technique requires no chemical preparation, does minimal damage to the sample and yields external reproducibility that is better than conventional TIMS analysis; ²⁰⁷Pb/²⁰⁶Pb =±0.015% 2σ in comparison with ²⁰⁷Pb/²⁰⁶Pb =±0.04% 2σ, respectively. We show that Pb isotope compositions give isotope fingerprints to mints despite the likely reworking of the metal during coin production.     

汉代铸钱夹砂陶背范的分析研究

与汉代铸钱相关的遗物中,铸钱夹砂陶背范出土数量最多,是由泥质面层与夹砂背层组成。为了揭示铸钱夹砂陶背范的制作工艺并探讨陶范多次使用的可能性及夹砂层的作用,对陕西西安窝头寨汉代铸钱遗址出土的铸钱夹砂陶背范进行分析研究。结果表明,泥质面层采用细泥料制作,其作用是保证所铸造的金属钱币具有优良的表面质量;夹砂背层是在制范泥料中掺杂了较多的肉眼可见的砂砾,其作用是提高陶范的机械性能,减小陶范受热后的变形,有利于它与金属范合范铸钱。铸钱夹砂陶背范的制作过程是:先制作夹砂层,然后在夹砂层上制作细泥层,在细泥层上印制钱币的背郭型腔,与金属范组成铸型铸造钱币。证实夹砂层可以重复使用,当泥质面层损坏后可以除掉表面的细泥层或直接在原型腔面上另加一层细泥重新制作背郭型腔,再次进行钱币的铸造,夹砂层可以一直使用到被损坏为止,从而极大地提高了铸钱效率。     

The circulation of precious metals in the Arab Empire: the case of the near and the Middle East*

The analysis by nuclear activation techniques and by inductively coupled plasma mass spectrometry combined with an UV laser of a large number of gold coins issued in the Arab Empire from the seventh to the 12th century ad showed that several different supplying sources were used, according to the region and to the period. The aim of this paper is to point out the circulation of gold in the Near and Middle Eastern mints of the Arab Empire and to make a parallel with the mints’ policies running in the other regions of the Empire, such as North Africa, the Iberian Peninsula and the Sicily. The identification of different gold ores by means of characteristic trace elements indicated recycling of the ancient coinage and, after ad 750, the minting in the entire Arab Empire of different new gold ores: Egyptian type, North Eastern type and West African type. The analysis of a small number of silver coins from the same periods and regions also showed a change in the ore supply after ad 750.     

庚子之后制钱铸造体系的规复与解体

制钱铸造在庚子之变中遭受重创,此后经历了一个艰难规复、地方实践、观念转型、民间转向与最终解体的复杂过程。面对庚子后的钱荒危机,清政府通过批准开铸铜元、重建中央铸钱局、改铸新制钱、推广粤式制钱等钱法改革,于光绪三十三年初步规复传统的制钱铸造体系。但随着各省对铜元余利的倚重与货币本位制改革的推进,朝野人士对主、辅币关系形成新的认识,铜元超越制钱被纳入主辅币方案,一文铜元亦在光绪三十四年逆转一文制钱成为推行全国的一文新钱。由此,钱法改革从属于本位制改革,政府币制改革观念亦由银钱并行、分层开展转型为统筹划一、建立银本位,故制钱被排除在新币制之外,长期亏赔的宝泉局最后亦被撤销。同时,民间私钱历经泛滥与衰落之后,在宣统朝转入消亡期。至宣统三年,虽然官私制钱仍在广泛流通,但相关铸造活动已全面停止,这标志着自秦代以后运行两千余年的传统铸钱体系最终解体。     

AN ANALYSIS OF THIRTY-ONE COINS FROM THE HELLENISTIC PERIOD

Thirty-one silver coins of the Hellenistic period were examined by the particle induced X-ray emission (PIXE) method, and the results incorporated into a wider study of the coins. Some tentative conclusions reached in the study are mentioned, together with an outline of the PIXE method. A number of patterns emerged in the results, the most important being an apparent deterioration in silver content among the later Seleucid and Ptolemaic issues; some high concentrations of particular elements were also noted.     

Metallurgical study on some Sasanian silver coins in Sistan Museum

Elemental analyses and microstructural studies of historical metal artifacts provide researchers with invaluable and priceless information about metal extraction technology and the procedure of creating artifacts. In addition, the information is helpful for knowing about the metallurgical processes of the artifacts. This study was conducted by a microscopic examination and elemental analyses of seven Sasanian silver coins preserved in the Sistan Anthropology Museum, Iran. For the purpose of this study, three methods were employed: first, the proton induced X-ray emission microanalysis (micro-PIXE), to determine the main and trace elements of the coins; second, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), to perform elemental analysis to identify impurities of the metal; and third, microstructural analysis of the coins which was carried out with an optical microscope (OM). The elemental analyses identified Ca, Cu, Ag, Au, and Pb in the coins. The high quantity of Ag in samples validated the application of advanced and accurate cupellation technology for refining silver and separating impurities from raw ore. The gold concentration in the coins indicated the use of non-galena ore for silver extraction. Additionally, the microstructural analyses of samples pointed to the application of thermo-mechanical processes on coins.     

THE USE OF SPECIFIC HEAT IN THE NON-DESTRUCTIVE ANALYSIS OF SILVER/COPPER ALLOY COINS

Using partly plastic apparatus, specific heats of coins have been found calorimetricly to an accuracy of ± 3% for most coins. For silver/copper alloys the specific heat varies approximately linearly with the weight percentage composition, so the latter can be calculated for coins of unknown composition.     

Enhancing Understanding of the Emergence of Global Trade: Analysis of 17th‐ to 19th‐Century Spanish Coins Recovered from Western Australian Shipwrecks Using Laser Ablation – Inductively Coupled Plasma – Mass Spectrometry (LA–ICP–MS)

This research uses legacy data from shipwrecks to further our understanding of global silver movement in the 17th to 19th centuries by analysing a collection of silver coins held by the Western Australian Museum. Three hundred and eighty‐nine silver coins were analysed for their trace element fingerprint in order to identify provenance. The coins are a selection from the ships Batavia, Vergulde Draeck, Zuytdorp, Rapid and Correio da Azia, all wrecked off the coast of Western Australia between 1629 and 1816. Analysis was undertaken using laser ablation – inductively coupled plasma – mass spectrometry (LA–ICP–MS), a relatively non‐destructive technique with a sensitivity of parts per million to parts per billion. Data were interpreted using linear discriminant analysis (LDA), which allowed the coins of known provenance to be sorted into identifiable subgroups on the basis of their trace and minor elemental fingerprints, while 27 unidentified coins were compared with this database and their mint of origin predicted. These results have implications for the provenance determination of archaeological artefacts of many materials.