Periodic Reporting for period 2 - SILVER (Silver Isotopes and the Rise of Money)
Reporting period: 2019-04-01 to 2020-09-30
Although the ancient link between money and precious metals has been progressively dissolved, the rise of silver money still resonates with modern economy. ‘What is money?’, a commodity or rather a standard of value, is still a modern question. This question is probably better formulated in societies in which credit was not as common as today, central banks did not exist, and different forms of metal coexisted, notably coinage, silverware, and cult objects.
The objectives of the SILVER project relate to these questions by using lead and silver isotopes as a tracer of metal extraction, minting, and circulation. Lead is a metal always found in trace amounts in silver objects and the relative proportions of its isotopes vary over a broad range in rocks as a result of uranium and thorium radioactivity and local geology. Lead isotopes have been used for half a century by numismatists to fingerprint the ore deposits serving as the source of silver. A major ambiguity is that lead used for smelting may simply be foreign to the silver ore. Silver isotopes, which have been introduced to numismatics by our group in 2011, are not affected by this ambiguity because they belong to the metal that carries the value. Their relative abundances, however, unfortunately vary over only a very narrow range since, contrary to Pb isotopes, the cause of variation is purely thermodynamic. Measuring silver isotope compositions therefore require more work to achieve the needed precision for them to be useful. The purpose of the proposal is twofold. First, the development of early coinage in Greece, Ionia, and the Eastern Mediterranean will be traced. The relative weight of each production locality and the proportion of minted metal will be assessed. Second, we aim at monitoring the advance of monetization of the Mediterranean through the rise and fall of the competing empires, notably Persia, Greece, Macedon, Carthage, and Rome. We hope that collaboration between geochemists with a strong analytical and geological background and expertise and experts of history and numismatics will be decisive in documenting the rise of money from a new perspective.
A survey of lead isotopes in denarii minted by the Roman Republic demonstrated a major gap between the coins struck during the 2nd Punic War and those produced during the second half of the 2nd century BCE and after, which demonstrates a major shift in silver supply. The next step was the study of correlated variations of silver and lead isotopes in Roman denarii, which showed that the coins of the 2nd Punic War were struck from recycled silver in bulk and pre-existing coinage corresponding to the war indemnities paid by Carthage at the end of the 1st Punic War. In contrast, the Roman silver coinage of the late 2nd century was struck from silver produced in Spain using smelting processes developed by Phoenician colonists since the 8th century BCE.
The Roman denarii contrast with the coinage of classic Greece and its colonies in their visible decoupling of silver and lead ores. The Greeks and most of their colonies seem to have been using local lead to extract silver, whereas Phoenicians, and after them Carthaginians and Romans, had to bring foreign lead to the sites of silver extraction. This suggests that the silver ores used by the Greeks were essentially lead carbonates and sulfides, whereas in the Iberian Peninsula silver-rich sulfates had to be combined with lead extracted from galena.
The gap of well over 60 years between the conquest of Iberia silver ore deposits during the 2nd Punic War and the onset of massive minting of silver coinage testifies to the misgivings of Rome with respect to money until the 2nd C. BCE. As attested to by the predominance of unminted silver displayed in the Roman triumphs of the 2nd century BCE, these qualms were shared by many Mediterranean cultures. Why the Roman Republic finally gave in to monetization, probably upon pressure of the bulging mass of copper asses, and engaged into mass production of silver denarii, is unclear. Regardless of the motivations, this period marks the generalization of money around the Mediterranean.