Aureus

The aureus (pl. aurei — "golden") was a gold coin of ancient Rome valued at 25 silver denarii. 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 is approximately the same size as the denarius, but is heavier due to the higher density of gold.

Before the time of Julius Caesar the aureus seems to have been a "currency of account,"a denomination struck very infrequently and not commonly seen in daily transactions due to its high value. Caesar struck the coin more frequently and standardized the weight at 1/40 of a Roman pound (about 8 grams). The aureus was probably most often struck to pay bonuses to the legions at the accession of new emperors. The mass of the aureus was decreased to 1/45 of a pound (7.3 g) during the reign of Nero.After the reign of Marcus Aurelius the production of aurei decreased, and the weight was further decreased to 1/50th of a pound (6.5 g) by the time of Caracalla. During the third century, gold pieces were introduced in a variety of fractions and multiples, making it hard to determine the intended denomination of a gold coin.  However, regardless of the size or weight of the aureus, the coin 's purity was little affected. Analysis of the Roman aureus shows the purity level usually to have been in excess of 99%, compared to 91.7% (22k) for the British sovereign and the 90% for the US gold dollar.

Due to runaway inflation caused by the Roman government 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 denarii grew drastically. Inflation was also affected by the systematic debasement of the silver denarius which by the mid-third century had practically no silver content. In 301 AD one gold aureus was worth 8331/3 denarii; by 324 AD the same aureus was worth 4,350 denarii. In 337 AD, after Constantine converted to the solidus, one solidus was worth 275,000 denarii and finally, by 356 AD, one solidus was worth 4,600,000 denarii.

Use of the same dies for both aurei and denarii was the rule up until Titus and continued in some issues until about Hadrian. Thereafter the style and size of the two denominations diverged, though gold and silver quinarii often continued to be struck from the same dies. The dies for Severan aurei are always larger and finer than the dies for denarii.

Constantine introduced the solidus in 309, replacing the aureus as the standard gold coin of the Roman empire. The solidus was a larger diameter and thinner coin.

1 aureus = 25 denarii
1 quinarius (gold) = 12 1/2 denarii
1 denarius = 16 asses
1 quinarius (silver) = 8 asses
1 sestertius = 4 asses
1 dupondius = 2 asses
1 as = 4 quadrantes
1 semis = 2 quadrantes
1 quadrans = 1/4 as

See Gold coinage of the Romans.


Moneta Historical Research by Tom Schroer

The "aureus" (plural: aurei) was a high-purity (99% fine) Roman gold coin issued from about 82 BC until 324 AD. The Roman Republic had issued gold only in two emergency issues during the Second Punic War (218 BC - 201 BC) until the dictator Lucius Cornelius Sulla (138 BC - 79 BC) issued gold about 82 BC. The earlier emergency issues, both extremely rare, were staters and half-staters issued about 218 BC, and 20-, 40-, and 60-as pieces from about 211-207 BC. Sulla issued the first gold coins which became known as "aurei".  They were equal to 25 denarii (see Denarius) until sometime in the third century AD.

Aureus is a Latin adjective which means "golden" (the noun "gold" is "aurum"). The name came because the new gold coin resembled the denarius in size and thus was referred to as a "golden" denarius.  The aurei of Sulla were struck at 30 to the Roman pound, or about 10.92 grams. In 71 BC Gnaeus Pompeius Magnus (Pompey the Great) issued an extremely rare issue of aurei at 36 to the Roman pound, or 9.10 grams.  Apparently the first large issues of aurei were by Julius Caesar (100 BC - 44 BC), who struck at 40 to the Roman pound, or 8.19 grams.  The Caesarian standard prevailed through the Imperatorial period into the principate of Augustus.

Augustus' aurei are usually 7.75 - 8.00 grams in weight and 19-20 millimeters in diameter. Under Tiberius the weight peak for aurei was about 7.75 grams, where it essentially remained until the coinage reform of 64 under Nero.  Nero reduced the weight to about 7.31 grams, and it drifted even somewhat lower (about 7.25 grams) by the time of Titus (79-81) before Domitian restored it to the pre-Neronian reform weight at about 7.58 grams.

Trajan struck the aureus at about the post-Neronian reform weight and the aureus finally stabilized there until about 215 when Caracalla reformed the coinage.  Besides introducing the "antoninianus", he established the aureus at a new standard of 50 to the Roman pound (6.55 grams). Macrinus inexplicably reverted to the pre-215 weight, but from 218 to 238 the aureus was again struck at 50 to the Roman pound.

From the tumultuous year of 238 until Diocletian the aureus reflected the fortunes of the Empire, fluctuating wildly and being completely unsettled.  Aurei of this period are rather rare and it has been suggested that the only circulation possible was by weight, since they varied from 4.19 grams under Trajan Decius to 6.2 grams under Probus.  Aemilian's aurei were even struck at about 3.4 grams!  Radiate-bust aurei were struck from about 251 onwards, but their weights are not heavy enough to be a true double, and a pattern is difficult to discern, although they were always heavier than the laureate-bust pieces. Carus and his family attempted to settle upon 70 to the Roman pound (4.68 grams each), although Numerian  and Carinus as Augusti seem to have moved to 60 to the pound (5.46 grams in theory, but usually struck between 5.3 and 5.4 grams). Diocletian initially struck at 70 to the pound, and took the step of putting the Greek numeral for 70 upon his aurei.  However around 290 he settled upon 60 aurei to the pound, and often marked them with the Greek numeral for 60.  The stability of the Tetrarchy kept the aureus at 60 to the pound until Constantine I in 309 or 310 issued his gold at 72 to the pound or 4.55 grams.  His coin is known as the "solidus", and it circulated alongside the aureus at the ratio of 6 solidi=5 aurei until in 324 the solidus became the new gold standard for the Roman world after the defeat of Licinius I in the Second Civil War.  The last aurei were thus struck by Licinius I from eastern mints in about 324, still at about 5.3 grams. Throughout the four centuries they were issued, their diameter was usually between 18-20 millimeters.