The Roman Aureus

Roman Gold Coins

The Aureus in the Republican Period

Gold coins were struck irregularly at Rome before Julius Caesar. The earliest gold issue, known as the oath gold (oro del giuramento), appeared around 220 BC following the metrology of Campanian didrachms, featuring Janus on the obverse and an oath-taking scene between two warriors over a sacrificial pig on the reverse (weighing 6.8 g, worth 8 silver didrachms).

During the Second Punic War (216–209 BC), gold fractions marked 60, 40, and 20 sestertii/asses (with the head of Mars and an eagle on a thunderbolt) were issued to finance emergency military expenditures.

Later, Sulla (82 BC, at 1/30 Roman pound = 10.9 g) and Pompey minted military gold issues. It was Julius Caesar in 46 BC who established regular gold striking, fixing the aureus at 1/40 of a Roman pound (about 8.18 g) with a fixed tariff of 25 denarii.

The Aureus during the Empire

Under Augustus, the aureus became the cornerstone of the imperial bimetallic currency system at 25 denarii (100 sestertii). Nero in 64 AD reformed its weight down to 1/45 pound (7.28 g) while maintaining gold purity near 99%.

During the 3rd-century crisis, successive emperors reduced its weight: Caracalla to 1/50 pound (6.5 g), and Diocletian to 1/60 pound (5.45 g). Finally, around 310–312 AD, Constantine replaced the aureus with the solidus at 1/72 pound (4.5 g), bringing gold stability to the Late Empire and Byzantium.