Discovering the sources of Roman silver coinage in the Iberian Peninsula

Despite its earlier status as a luxury commodity, silver became widely used for currency in the Roman world from the 7th century BCE and provided a standardized monetary system for ancient Mediterranean civilizations. However, the sources of silver used to produce Roman coinage have been largely depleted, making it difficult to determine the deposits mined by Roman miners.

A new study published in the journal Geology yesterday assessed the silver sources of different mining provinces of the Iberian Peninsula to determine which places may have been mined silver to produce Roman coins.

“Controlling silver sources was a major geopolitical issue, and identifying Roman silver sources can help archaeologists reconstruct ancient flows of precious metals and answer important historical questions,” Jean said. Milot, the lead author of this study.

The Iberian Peninsula, which includes modern Spain and Portugal, is home to world-class silver deposits, especially in the southern region. These deposits contain galena, which is the main ore of lead and an important source of silver. To extract the silver, galena ore is smelted and purified, with refined silver for minting coins up to a purity of over 95%.

To track the source of Roman silver, the team of researchers analyzed the silver and lead compositions of galena samples from ore deposits across the Iberian Peninsula and compared the results to the coins’ chemical signatures. of Roman silver coins.

They identified two different types of galena deposits based on the elemental silver composition of the samples: silver-rich galena which would have been a likely source for Roman coinage, and silver-poor galena which would have been mined only for gold. lead and would have been of less economic importance.

However, few ore samples had a composition that matched the elemental silver composition of Roman silver coins. Silver ores covered a wide range of compositional variability, but Roman coins notably have a very narrow range of elemental composition.

Based on the elemental lead signatures of the galena samples, ore deposits in southeastern Spain best match the composition of Roman coins, suggesting that these deposits were a major source of silver Roman. Both silver-rich and silver-poor galena deposits were probably mined here, as the lead mined from the silver-poor galena could be mixed with other ores to extract the silver.

These results based on chemical analyzes are also consistent with archaeological evidence of ancient mining in the area.

This combined analytical toolkit provides a means of distinguishing between silver-rich deposits and deposits devoid of silver ore, which is essential for understanding the dynamics of silver supply in Roman times.

“This work needs to be extended to the silver-rich region in which coinage was invented in the 6th century BCE, Greece and Asia Minor (modern Turkey),” Milot said. “The method we describe here will allow us to recognize the lost ore fields that provided silver to the Eastern Mediterranean empires from the Bronze Age to the collapse of the Hellenistic kingdoms.”

Source of the story:

Materials provided by Geological Society of America. Note: Content may be edited for style and length.

David C. Barham