This lesson explores billon, a copper–silver alloy widely used in coinage from antiquity to the medieval period. By examining coins from different eras, we will see how the silver content varied depending on the economic and political context, and how this variation can be studied through XRF analysis.
Objectives
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Understand the definition and characteristics of billon.
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Compare coins of different historical periods based on their silver content.
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Interpret XRF spectra to distinguish between high-, medium-, and low-silver billon.
Materials
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Selected coin samples:
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Tetradrachm of Hadrian, Alexandria (2nd century CE).
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Antoninianus of Gallienus (3rd century CE).
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Denaro picciolo of Perugia (14th century).
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Lesson Plan
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Introduce the concept of billon and its historical significance.
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Present the Hadrian tetradrachm as an example of high-silver billon.
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Discuss the Gallienus Antoninianus as a medium-silver billon coin, reflecting imperial decline.
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Examine the Perugian denaro picciolo as a low-silver billon coin of the medieval period.
