Watch Solidus Byzantine Coin Vol II

The solidus (the Latin word for solid) was originally a gold coin issued by the Romans. The solidus was first introduced by Diocletian around 301, struck at 60 to the Roman pound of pure gold and with an initial value equal to 1000 denarii. However, Diocletian's solidus was only struck in small quantities, and thus had only minimal economic impact. The solidus was re-introduced by Constantine I in 312, permanently replacing the aureus as the imperial gold coin of the Roman Empire. The solidus was struck at a rate of 72 from a Roman pound of pure gold, each coin weighing twenty-four Roman/Greek carats, or about 4.5 grams of gold per coin. By this time, the solidus was worth 275,000 increasingly debased denarii. The solidus maintained essentially unaltered in weight and purity until the 10th century, though in the Greek-speaking world during the Roman period and then in the Byzantine economy it was known as the NOMISMA (plural nomismata). Whenever the coin was taken in by the treasury, it was melted down and reissued. This maintained the evenness of the weight of the circulating solidi, since the coin did not tend to be in circulation for long enough to become worn. Minting of the gold coin - unlike the base-metal coins of the time - had no permanently established minting facility. Due to the requirement that taxes were paid in gold, solidus minting operations tended to follow the emperor and his court. For example, solidi were minted in Milan in 353, and in Ravenna after 402. Each of these locations were imperial residences at those times. Although merchants were forbidden from using solidi outside of the Byzantine empire, there was sufficient trade in these coins outside of the empire that they became a desirable circulating currency in Arabic countries. Since the solidi circulating outside the empire were not used to pay the taxes to the emperor they did not get re-minted, and the soft pure gold coins quickly became worn. Through the end of the 7th century,