Gold and silver were an integral part of business and trade as far back as the early civilizations of Sumer (the land between the rivers Euphrates and Tigris in what is now Iraq) and Egypt.

The great French historian Fernand Braudel saw these precious metals as the "lifeblood of Mediterranean trade in the 2nd millennium BC". Initially, however, they were traded simply by weight in the form of ingots, which could then be cut up into small chunks or drawn into wire. And the metals, particularly silver, were regarded more as a standard of accounting or for taxes to rulers or temples, rather than for general circulation among the population.

The first real coins were not struck until the 6th century BC in Lydia (Western Turkey). They were made from electrum, natural alloy of gold and silver found in the rivers of the region. They usually had a lion or a bull on one face and a punch mark or seal on the other, and weighed from 17.2 grams (0.55 troy oz) to as little as 0.2 grams (.006 troy oz). Their introduction is attributed to the Lydian king Croesus (561-547 BC). Improvements in refining soon led to the distinct minting of gold and silver coins.

Coinage was swiftly taken up in the blossoming Greek city states just across the Aegean sea, though it was predominantly of silver until Philip II of Macedon (359-336 BC) acquired gold and silver mines in Thrace (now Bulgaria). His son, Alexander the Great (336-323 BC) then consolidated the Greek Empire with his conquest of the Persian empire, securing an immense gold treasure built up by the Persians from gold sources on the river Oxus in northern Afghanistan. Alexander is reputed to have taken over 22 metric tonnes (700,000 troy ounces) of gold coins in loot from the Persians. For both Philip II and Alexander, gold coin became an essential way of paying their armies and meeting other military expenses. Under the Greek empire, the coins were stamped with the head of the king instead of lions, bulls and rams that had previously adorned gold coins elsewhere.

The Romans, for whom gold coins became the crucial way of paying their legions, also adopted the custom of striking the emperor's head on their gold aureus coin. The aureus was usually 950 fine (22 carat) and weighed 7.3 grams (0.23 troy oz); 45 aurei weighed one roman pound (libra).

Although this coin was too valuable for most daily transactions, they were used by administrators, traders and for army pay (a legionnaire was paid one aureus each month).

In Britain, one aureus bought 400 litres (28.57 gallons) of cheap wine or 91 kilos (200 pounds) of flour. A smaller gold coin, the solidus, weighing 4.4 grams (0.14 troy oz) was introduced after 300 AD, as gold supplies from Spain and Eastern Europe declined.

The Romans minted gold coins on a scale not seen before and not equalled until modern times. Between 200 and 400 AD hundreds of millions of coins were struck and distributed throughout the empire. The extent of circulation is demonstrated by the hoards of roman coins that have turned up across Europe, particularly in Britain, which can be seen in many museums, notably the British Museum in London.

The British Museum's HSBC Money Gallery provides a unique display of the evolution of early gold coins.

The Roman empire brought a remarkable unity to much of western Europe through coherent public institutions and coinage. When that empire fell apart soon after 400 AD, it was almost one thousand years before widespread gold coinage returned. The solidus survived as the main gold coin of the Mediterranean world, being minted by the Byzantine emperors in Constantinople as the nomisma or bezant.

Solidus
Constantine introduced a new gold coin in his reign, to replace the aureus, which was called the solidus and was 1/72 of a pound.
Scripulum
This was another gold denomination introduced by Constantine, worth 1 1/2 of a solidus.
Semissis
was a smaller gold coin introduced by Constantine, and was worth 1/2 of a solidus. It was replaced in the reign of Theodosius I.
Tremissis
The tremissis was introduced by Theodosius I to replace Constantine's scripulum, and was worth 1/3 of a solidus.

The aureus was the main gold coin of the Early Empire, and its minting was under the direct control of the Emperor. Under Augustus, the currency was such:
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

Roman gold coin - sent for ID 19.6mm, 7.81g