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Bronze, Brass and Orichalcum

The sestertius, a coin worth four asses and dupondius, worth two asses were both struck in orichalcum brass. The as was about the same size as the dupondius but was struck in more or less pure copper, which was much resser than the brass when newly minted. This fine example from the author's collection bears the portrait of the Roman emperor Domitian.

It is surprising to many modern students of history to find out that the Greeks and Romans could control very precisely the percentage of each different metal that went into their alloys. The fineness or proportion of precious metal in an alloy was most important in commerce and archaeological research has shown that the Romans could control the finess of gold in their coins and ingots to within one percent. This degree of control not only allowed the Romans to closely guard the purity of their gold and silver coins but allowed them to cheat accurately as well!

An alloy of copper and zinc called orichalcum was used a great deal by the Romans. This consisted of eighty percent copper and twenty percent zinc, with small amounts of lead, tin, and other metals and would be called yellow brass today.

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