Aureus
The aureus ( aurei, 'golden', used as a noun) was a gold coin of ancient Rome originally valued at 25 pure silver denarii (sin. denarius). The aureus was regularly issued from the 1st century BC to the beginning of the 4th century AD, when it was replaced by the solidus. The aureus was about the same size as the denarius, but heavier due to the higher density of gold (as opposed to that of silver). Before the time of Julius Caesar the aureus was struck infrequently. Caesar struck the coin more often, and standardized the weight at of a Roman pound (about 8 grams). Augustus () tariffed the value of the sestertius as of an aureus. The mass of the aureus was decreased to of a Roman pound (7.3 g) during the reign of Nero (r. 54–68). At about the same time the purity of the silver coinage was also slightly decreased. After the reign of Marcus Aurelius (r. 161–180) the production of aurei decreased, and the weight fell to of a Roman pound (6.5 g) by the time of Caracalla (r. 211–217). During the 3rd century, gold pieces were introduced in a variety of fractions and multiples, making it