Aureus

aurei, 'golden', used as a noun) was a gold coin of ancient Rome originally valued at 25 pure silver denarii (sin.

The aureus was about the same size as the denarius, but heavier (since gold has a higher density than silver).

[2] The solidus was first introduced by Diocletian (r. 284–305) around 301 AD, struck at 60 to the Roman pound of pure gold (and thus weighing about 5.45 g each) and with an initial value equal to 1,000 denarii.

[2] However, Diocletian's solidus was struck only in small quantities, and thus had only minimal economic effect, although its stable weight brought an end to the instability that had existed for a while.

Analysis of the Roman aureus shows the purity level usually to have been near to 24 carat gold, so in excess of 99% pure.

Due to runaway inflation caused by the Roman government's issuing base-metal coinage but refusing to accept anything other than silver or gold for tax payments, the value of the gold aureus in relation to the denarius grew drastically.

Today, the aureus is highly sought after by collectors because of its purity and value, as well as its historical interest.

The most expensive aureus ever sold was one issued in 42 BC by Marcus Junius Brutus, the assassin of Gaius Julius Caesar, which had a price realized of $3.5 million in November 2020.

An aureus, issued by the emperor Alexander Severus (r. 222–235), has a picture of the Colosseum on the reverse, and had a price realized of $920,000 in 2008.