Aureus
Ancient Roman gold coin
Aureus (plural: aurei) was a type of gold coin in ancient Rome. It had the same value as 25 denarii silver coins. An aureus was the same size as a denarius, but it weighed more because gold is more dense.
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The aureus coin was first used in 1st century BC. It stopped being used in the 4th century AD. It was replaced by the solidus.