Periodic Reporting for period 3 - RACOM (Rome and the Coinages of the Mediterranean: 200 BCE to 64 CE)
Reporting period: 2022-09-01 to 2024-02-29
Ancient silver coinage formed the backbone of state finance in antiquity. The fineness and quality of a coinage is often taken by historians to be a comment on the fiscal health of the issuing state, yet very little is really known about its fineness and chemical composition, leaving historians guessing about financial strategies and sources of metals. Many previous analyses were inadequate to answer key questions, because the samples for analysis were commonly taken from the surfaces, or from just beneath the surfaces, of silver coins, and these are not representative of the original alloys used.
The historical period covered by the RACOM Project, from c. 150 BCE to 64 CE, is important in the economic development of the Mediterranean world. It witnessed a major increase in long distance trade and probably also economic growth and a rise in per capita income. Roman conquest led to greater economic and monetary integration of the Mediterranean area, and Rome’s apparent currency monopoly may have had consequences for the development of coinage and management of finances. Flows of precious metals to Rome and other important centres of power helped finance Roman expansion. Understanding the chemical composition of silver coinage will transform our understanding of Roman monetary strategy as an instrument of imperialism.
The objective is to examine financial and monetary strategies during that time through detailed analyses of the chemical composition of all major silver coinages of the period, taking samples from deep within the coins. Corrosion alters the composition of the surfaces and sub-surfaces of the coins, and sometimes the coins were deliberately treated at the mint to alter their surface composition, meaning that it is only in the heart metal of the coin that the original 'recipe' for the coinage is preserved. It is this recipe that constituted the controllable feature of coin quality and informs us about fiscal policy. The samples are then analysed by two complementary, well-established techniques (microwave-plasma atomic emission spectrometry; and inductively-coupled plasma mass spectrometry). Lead isotope analyses are also undertaken on select samples.
Taking drilled samples from museum coins is not always possible, and the project evaluates two new, minimally destructive, or non-destructive, techniques to see how they compare with established protocols: muon X-ray Emission Spectroscopy; and Laser Ablation Inductively Coupled Mass Spectrometry.
The historical period covered by the RACOM Project, from c. 150 BCE to 64 CE, is important in the economic development of the Mediterranean world. It witnessed a major increase in long distance trade and probably also economic growth and a rise in per capita income. Roman conquest led to greater economic and monetary integration of the Mediterranean area, and Rome’s apparent currency monopoly may have had consequences for the development of coinage and management of finances. Flows of precious metals to Rome and other important centres of power helped finance Roman expansion. Understanding the chemical composition of silver coinage will transform our understanding of Roman monetary strategy as an instrument of imperialism.
The objective is to examine financial and monetary strategies during that time through detailed analyses of the chemical composition of all major silver coinages of the period, taking samples from deep within the coins. Corrosion alters the composition of the surfaces and sub-surfaces of the coins, and sometimes the coins were deliberately treated at the mint to alter their surface composition, meaning that it is only in the heart metal of the coin that the original 'recipe' for the coinage is preserved. It is this recipe that constituted the controllable feature of coin quality and informs us about fiscal policy. The samples are then analysed by two complementary, well-established techniques (microwave-plasma atomic emission spectrometry; and inductively-coupled plasma mass spectrometry). Lead isotope analyses are also undertaken on select samples.
Taking drilled samples from museum coins is not always possible, and the project evaluates two new, minimally destructive, or non-destructive, techniques to see how they compare with established protocols: muon X-ray Emission Spectroscopy; and Laser Ablation Inductively Coupled Mass Spectrometry.
The first part of the RACOM Project is designed as the analytical phase, involving the gathering of data through sampling and compositional analysis of coins, metrology, and the study of coin hoards. Between September 2019 and February 2020 a large proportion of the selection and sampling of coins was undertaken in major museums in the UK, the USA and Switzerland. By the end of February 2020 we had sampled 1,732 coins. These samples have now all been analysed, and permissions are being sought to sample coins in other museum collections in the UK, Europe and Israel. Full results and numismatic details (including images) are housed on the project database.
An additional 96 coins for the project have so far been acquired through Messrs Baldwin in London. Two experimental runs have taken place at the ISIS Muon and Neutron Source, on 31 coins from various sources, which is more than expected for the reporting period. As an add-on to the project, neutron tomography on 4 coins illustrated the changes between their surfaces and interiors.
Two postdoctoral fellows were appointed: one to work on laser ablation; the other on coin circulation. Study of coin metrology is ongoing, using data from specific gravity measurements in combination with weights and analytical results.
Analytical results so far provide the first detailed map of composition of 976 Roman Republican silver coins. Muon analysis provides silver and copper levels for 31 coins, some of which are too thin to drill. The possibility of using muonic X-ray and gammas for isotope analysis is being explored; it has now been confirmed for lead, and work continues on silver.
An additional 96 coins for the project have so far been acquired through Messrs Baldwin in London. Two experimental runs have taken place at the ISIS Muon and Neutron Source, on 31 coins from various sources, which is more than expected for the reporting period. As an add-on to the project, neutron tomography on 4 coins illustrated the changes between their surfaces and interiors.
Two postdoctoral fellows were appointed: one to work on laser ablation; the other on coin circulation. Study of coin metrology is ongoing, using data from specific gravity measurements in combination with weights and analytical results.
Analytical results so far provide the first detailed map of composition of 976 Roman Republican silver coins. Muon analysis provides silver and copper levels for 31 coins, some of which are too thin to drill. The possibility of using muonic X-ray and gammas for isotope analysis is being explored; it has now been confirmed for lead, and work continues on silver.
The RACOM Project has already generated the largest and most comprehensive set of analyses of Roman Republican and late Hellenistic Greek coinages ever, and several hundred more samples and analyses are anticipated, with forthcoming sampling visits to museum collections in Europe and Israel. Results show changes to metal procurement strategies in Mediterranean mints, differences in refining and technologies of coin production. They also highlight a greater extent of debasement of some coinages than was thought previously.
They provide a new perspective on Roman Republican silver, challenging standard accounts of the purity of the coinage. There are many different and distinct phases representing technical and supply issues, as well as reflecting political and financial conditions. Closer study of the composition of individual issues can now confirm/challenge the dating of those where the date has been debated, helping to refine the chronology.
The use of Muon XES allows us to analyse the interior composition of small, thin coins that cannot be sampled using a drill. This has been particularly useful for Greek coinages. Muon analyses have produced consistent results and show that the fineness of Greek coins varies by region, reflecting circulation patterns. Muonic x-ray and gamma analysis has been confirmed as a method for measuring lead isotopes.
Metrological work shows that corrosion has had a major effect on the weights of many silver/copper alloy coins in museums, so that they do not preserve the original weight standard. Using knowledge of the original fineness, the current weight and specific gravity and the expected specific gravity allows us to estimate the original weight of the coins and determine standards more clearly. By the end we expect to have clear metrological data on debased coinages, particularly those of the Seleucid and Ptolemaic kings. The compositional and metrological work will inform the study of coin circulation, looking for changes to patterns of use following changes to the coins. Comparison of laser ablation with MP-AES, ICP-MS and M-XES will evaluate for the former as an analytical technique.
There are opportunities for synergies with the H2020 SILVER Project; members of both projects attend each other’s events and a team member of SILVER is an Advisory Panel member of RACOM.
Much more is to come. The implications of the new data from the RACOM Project are so wide-ranging that they will have an impact far beyond the lifetime of the RACOM Grant itself.
They provide a new perspective on Roman Republican silver, challenging standard accounts of the purity of the coinage. There are many different and distinct phases representing technical and supply issues, as well as reflecting political and financial conditions. Closer study of the composition of individual issues can now confirm/challenge the dating of those where the date has been debated, helping to refine the chronology.
The use of Muon XES allows us to analyse the interior composition of small, thin coins that cannot be sampled using a drill. This has been particularly useful for Greek coinages. Muon analyses have produced consistent results and show that the fineness of Greek coins varies by region, reflecting circulation patterns. Muonic x-ray and gamma analysis has been confirmed as a method for measuring lead isotopes.
Metrological work shows that corrosion has had a major effect on the weights of many silver/copper alloy coins in museums, so that they do not preserve the original weight standard. Using knowledge of the original fineness, the current weight and specific gravity and the expected specific gravity allows us to estimate the original weight of the coins and determine standards more clearly. By the end we expect to have clear metrological data on debased coinages, particularly those of the Seleucid and Ptolemaic kings. The compositional and metrological work will inform the study of coin circulation, looking for changes to patterns of use following changes to the coins. Comparison of laser ablation with MP-AES, ICP-MS and M-XES will evaluate for the former as an analytical technique.
There are opportunities for synergies with the H2020 SILVER Project; members of both projects attend each other’s events and a team member of SILVER is an Advisory Panel member of RACOM.
Much more is to come. The implications of the new data from the RACOM Project are so wide-ranging that they will have an impact far beyond the lifetime of the RACOM Grant itself.