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.     

A STUDY OF THE SILVERING PROCESS OF THE GALLO‐ROMAN COINS FORGED DURING THE THIRD CENTURY AD*

We have observed by fast neutron activation analysis (FNAA) that the global composition of the official silver coins of the Gallic emperor Postumus is not the same as those from the contemporary unofficial mints. In order to explain this phenomenon, we have carried out a metallographic study of the artefacts. Then, we have re‐created the silvering process of unofficial coins in order to better understand the manufacturing process of silvering. The different steps of the replication process are explained in this paper.     

Chronological discrimination of silver coins based on inter‐elemental ratios using laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS)

This paper details the application of a statistical method for the chronological discrimination of silver coins using counts per second trace elemental, inter‐elemental ratios. The statistical method described is based on a method that has been applied to similar archaeological materials to determine their provenance. The method makes use of the inter‐element association patterns of multi‐element analytical data determined using laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS). The majority of the 266 coins analysed for this study have already been successfully identified by their mint markings. The data from LA‐ICP‐MS analyses, together with what is known about the coins through visual identification, were used to discriminate the reigning sovereign, and in the case of Mexico, the year of minting, of individual coins within the elemental fingerprint of different mints. Subsequently, unidentified coins can be placed in the confusion matrix, and their trace element information used to identify their year of minting when compared with other, identified coins from the same mint. The interpretational statistical technique linear discriminant analysis (LDA) was used to explore an identification of year of minting of coins that have previously not been identified by other means based on a statistical comparison against a database of compositional analysis of silver coins of known year of minting.     

Potentialities of X-ray fluorescence analysis in numismatics: the case study of pre-Roman coins from Cisalpine Gaul

X-ray fluorescence (XRF) is a well-known technique for the analysis of ancient metals. Thanks to the availability of portable instruments (p-XRF), it is extensively used for the chemical characterization of coins directly in museums. In this work, the potentialities of the technique have been investigated, through its application to a case study concerning the Cisalpine Gaul coinage. More than 200 drachmas have been analysed to discriminate different productions on the base of minor elements. Major elements, on the other hand, have been used to trace alloy changes through the centuries. As concerns the quantification of the silver content (fineness), XRF and neutron diffraction results have been compared, in order to check the presence of surface-enriched layers.     

NEUTRON ACTIVATION ANALYSIS OF BIRD BOWLS AND RELATED ARCHAIC CERAMICS FROM MILETUS

In this paper we present the results of a chemical investigation by neutron activation analysis of sherds of different kinds of bird kotylai, bird bowls and related wares excavated in Kalabaktepe, a hill of the ancient city of Miletus. A new archaeological classification of this well-known group of Archaic ceramics of eastern Greece is presented. A number of kiln wasters of misfired vessels from Kalabaktepe revealed a characteristic local pattern. This pattern helped to clarify the provenance of some of the bird bowls classified archaeologically as of orientalizing type: they have been made in Miletus. But bird kotylai and bird bowls in the 'standard fabric’as well as other archaeologically related vessels show a different chemical pattern of unknown provenance.     

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.     

ANALYSIS OF COPPER-BASED METALLIC ARTIFACTS BY PROMPT GAMMA-RAY NEUTRON ACTIVATION ANALYSIS

Non-destructive analysis of the major elements in copper-alloyed artifacts by prompt gamma neutron activation analysis is reported. Copper, zinc, tin and lead were measured in several ancient Roman, Greek and Iranian objects. Good agreement was found in comparison with analysis of similar objects by destructive methods.     

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.     

THE ANALYSIS OF GOLD COINS—A COMPARISON OF RESULTS OBTAINED BY NON-DESTRUCTIVE METHODS

This paper discusses a systematic difference between the results found when one series of Dark-Age gold coins were analysed both by neutron activation and by specific gravity analysis and when a second series of similar coins was analysed by the Oxford Milliprobe and by specific gravity. No reason is given for this systematic difference, although there is evidence that all three methods are slightly in error, two of them giving results for gold which are too high and the specific gravity method giving results which are too low.     

A Study on the Xiwang Shanggong Coins Unearthed at the Jiangkou Site in Pengshan,Sichuan

An archaeological excavation was jointly conducted by organizations including the Sichuan Provincial Cultural Relics and Archaeology Research Institute in the first half of 2017 in the Jiangkou stretch of the Minjiang River in Pengshan District, Meizhou, Sichuan Province, where more than two hundred gold and silver xiwang shanggong coins were unearthed. This was the first time that the existence of xiwang shanggong coins was proved by a systematic archaeological excavation, providing a scientific basis for solving the long-standing unresolved historical problem. By sorting out the academic history of xiwang shanggong coins, this paper points out that in the past seven years, these coins have experienced the transition from being dug by robbers to being excavated scientifically, and have turned from a hot topic in collection to one in academia. This paper summarizes the characteristics of these gold and silver coins and presents an idea that those coins may have never been officially issued. Some of the coins have residual traces of being burnt, which may provide physical proof to prove the event in historical records that the fleet of Zhang Xianzhong was burnt by the army of Yang Zhan in the early Qing Dynasty. By using these unearthed xiwang shanggong coins as the standard and comparing them with some of the handed-down counterparts, this paper makes an in-depth analysis on the authenticity of the handed-down coins and indicates that some of the gold and silver ones may be authentic while some copper ones may be counterfeit.     

NEUTRON ACTIVATION ANALYSIS OF FAIENCE BEADS

A selection of faience beads has been examined using neutron activation analysis, with a view to distinguishing the provenance of individual specimens. Evidence is presented that the tin content in beads from British sites is significantly higher than in those from other areas. Characteristic features of beads from other sources are also discussed.     

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.     

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.     

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.     

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.     

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.     

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.     

ION BEAM ANALYSIS OF COPPER AND COPPER ALLOY COINS

In recent years ion beam techniques have become more and more important since in most cases the analysis of copper and copper alloy coins has to be non-destructive. It is therefore of interest to study the relative advantages of several nuclear methods for a certain type of metal. The results are presented here of a comparison between three non-destructive ion beam techniques: particle induced X-ray emission, proton activation analysis and fast neutron activation analysis.     

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.     

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.