Coinage reform of Augustus
Augustus brought the minting of gold and silver coins, the aureus and denarius, under his personal control without changing their weight or fineness. The gold aureus, weighing about one-quarter ounce, was worth twenty-five silver denarii, weighing about one-seventh of an ounce.
Augustus more comprehensively reformed denominations below the denarius. New ratios were fixed among the currencies: the sestertius was now minted from about an ounce of orichalcum, an alloy of copper and zinc, rather than silver, and fixed at a quarter of a denarius. The dupondius, formerly a two-pound bronze coin, was now orichalcum, valued at half a sestertius and weighing half as much. The half-ounce as, worth half a dupondius, the semis, worth half an as, and the quadrans, worth half a semis, were the first pure copper coins minted in Rome since 84 BC.
- Cartwright, Mark. "Roman Coinage". Ancient History Encyclopedia. Retrieved 21 April 2016.
- Crawford, Michael. Coinage and Money Under the Roman Republic: Italy and the Mediterranean Economy. pp. 257–258, 260.