The first coins of the world, minted in electrum, were staters and their fractional parts. The most common size of the earliest coins was the 1/6th stater – called a “Hekte.” These small coins were about 10 mm in diameter and were not the smallest denomination. Interestingly the ancient die cutters were able to put intricate design details into coins as small as 5 mm.
Silver and Gold Staters
When the first silver and gold coins were minted, there were both silver and gold staters. Although these terms referred to weights of the coins, there existed different weight standards for these coins in different cities. Gold staters remained the main denomination of gold coins for most of the Greek era.
Drachms and Tetradrachms
The basic Greek silver coin in the Greek Empire was the drachm. By the time that these coins appeared, the weight standards were more consistent. The drachm was approximately 3.5 grams, and the tetradrachm (4 drachm coin) was 14 grams.
For further reading on common types of Greek ancient coins, read this Info-Vault article about the Coins of Alexander the Great.
The denarius was the major Roman silver coin for over 400 years until economic pressures led the emperors to gradually devalue the coins. The Roman Republic coins were minted from 200 BC until the time of Julius Caesar. Though the designs changed drastically beginning with Emperor Augustus – the Roman Imperial denarius coins continued to have the same 3.5-gram weight. In the years 200-275 AD, the amount of silver in these coins decreased from 95% down to 2-3%. In the end, the coins were most bronze with a silver coating.
For further information, read this Info-Vault article about the Roman Silver Denarius.
The gold aureus began in the first century BC with a weight of about 8 grams and was equal to 25 denarius coins. By the year 200, during the reign of Caracalla, the weight was reduced to 6.6 grams. During the time of Constantine the Great, it was later replaced by the Solidus with a weight of 4/5 grams.
Just as there is no clear change from the Roman to the Byzantine Empire, there is no clear move from Roman to Byzantine coins. The Solidus remained the gold coin of the Byzantines for a few hundred years until it was replaced by the Numisma. (Note that the Numisma is the basis for the word for the study of coins – Numismatics.)
Although there were millions of bronze coins minted during the 1000 years of coins before the Byzantine Empire, most of the bronze coins did not have specific denomination names. But in the Byzantine Empire, the main coins were bronze and were called by the amount of Nummi in each coin. For example, the large 40 nummi coin had a large M (meaning 40) on it.
For further reading on Ancient Coins, check out this Info-Vault article titled Top 5 Ancient Coins for Beginners.