If we were to ask about a metal alloy used since the beginning of history, the unanimous answer would surely be bronze. And, in fact, this combination of copper and tin gives its name to a whole period of prehistory, so that we could perhaps consider it the most important until the appearance of others. Of the ancient alloys, probably the most significant case was the electrum, which mixed gold and silver, which had a certain prestige.
Of course, there were more alloys in those remote times. There was hepatizon or black Corinthian bronze (copper or bronze alloyed with gold and silver); brass (copper with zinc), Indian panchaloa (made of the five sacred metals, gold, silver, copper, iron and zinc) or those that combined gold with copper, such as the tumbaga of pre-Hispanic America and the Japanese shakudō. These are just a few, since others could be cited, including those of more uncertain composition, such as the Oricalc or the Tibetan Thokcha.
Electrum, we said, is composed of gold and silver; it has a proportion of four parts of the first and one of the second, but there are also traces of other metals such as platinum or, above all, copper. This is because it is not an artificial alloy but a natural one, although it can also be manufactured, in which case the composition percentages change a little and the gold is reduced. How much? It depended on the place. Chemical analysis of Phocaean coins reveals that they were 55% gold, but in Lydia it could be even lower, between 55 and 45%; in Anatolia, on the other side, there were electrum with an amount of gold between 70 and 90%.
As you can see, we go back to Greek antiquity and, in fact, electrum is mentioned in The Odyssey and in the Book of Ezekiel. Now, the Homer poem is dated between the 8th and 7th centuries BC, and the Hebrew prophet’s one after that. There are even older sources: the first documented account of the expedition that pharaoh Sahure sent to the country of Punt in the 25th century B.C. tells that significant quantities of myrrh, malachite and electrum were brought from there. We also know that this alloy was used to cover the pyramidion, that is, the summit of the obelisks and pyramids, making it shine because that was where heaven and earth were joined and, therefore, where the solar disk representing Ra was placed.
Of course, it had other less metaphorical uses – vases, tools – and the most obvious was coinage. In fact, the first metal coins were made with electrum. They were found in the Temple of Artemis, in Ephesus, and are dated between 625-600 BC, during the reign of Alyattes, the fourth king of the Mermnad dynasty, although some historians go back further in time, to the period of King Gyges, the founder of that dynasty.
It was Alyattes who brought splendour to Lydia, thanks to the important coinage favoured by the abundance of gold in the Pactolus River, which gave rise to the myth of King Midas. Alyattes coins are usually stamped with a lion’s head, the symbol of the dynasty, and were the first to standardize their weight, so that an electrum stater was equivalent to 168 grains of wheat.
The stater was the usual monetary unit in the Hellenic world and, by extension, in the entire Mediterranean until the Romans introduced the denarius. Gold staters were also minted, although in a very localized manner and used as an accounting unit rather than as currency.
However, the electrum tended to prevail over the gold in coins because it was harder and, therefore, presented greater resistance over time and, on the other side, in those first coinage measures the technique of refining gold was focused only on specific sites. Moreover, gold was extracted in abundance from the deposits of the Lydian mountain Tmolo and from the alluvial deposits of the Pactolus river. However, the problem with electrum ( the natural one at least) was that it was not possible to know exactly what percentage of gold it had, which made the valuation of the currency difficult and had a negative impact on trade.
The solution was to introduce kroisos, a pure gold or silver stater, unalloyed and easy to value. Lydia was also the place of its appearance but now during the reign of Croesus, son of Alyattes and last king of the mentioned Mermnad dynasty. This monarch took possession of all the Greek polis of Asia Minor and created an ephemeral (fourteen years) but very prosperous empire, to the point that the word Croesus is today synonymous with rich.
Kroiseoi weighed about 10.7 grams, although over time they tended to reduce that weight to 8.1 grams with the aim of eliminating the devalued electrum, although these continued on the de facto market until the second half of the 4th century BC. After their conquest of Lydia, the Achaemenids continued to mint kroiseoi in Sardis until 515 BC. Darius I replaced them with persian Darics, which could also be made of gold or silver but weighing 8.4 grams.
The Greeks called the amber electrum, so the name they used to refer to that metal was white gold, probably because it often – not always, it depended on the proportion of silver in it – had a less intense brightness than normal gold. Nowadays, the term white gold is used to designate a gold alloy with some metal such as nickel, manganese or palladium, which is usually applied in jewellery instead of platinum because it is cheaper than it.
White gold was named green gold if it was artificial electrum. Interestingly, green gold had a very particular use until recently, a few decades ago: it was the alloy used to make Nobel Prize medals, which were later given a gold-plated finish.
Sources: Historia del dinero (Jonathan Williams y Catherine Eagleton) / Coins, bodies,games, and gold. The politics of meaning in Archaic Greece (Leslie Kurke) / New archaic coin finds at Sardis (Nicholas Cahill y John H. Kroll) / Héroes viajeros. Los griegos y sus mitos (Robin Lane Fox) / Money and monetary policy in Early Times (A. R. Burns) / Metrological Notes on the ancient electrum coins struck between the Lelantian Wars and the accesion of Darius (Barclay Vincent Head) / The Oxford Handbook of Greek and Roman Coinage (William E. Metcalf) /Wikipedia