Electrum is a naturally occurring alloy of gold and silver, with trace amounts of copper and other metals. It has also been produced artificially, and is often known as green gold. The ancient Greeks called it 'gold' or 'white gold', as opposed to 'refined gold'. Its colour ranges from pale to bright yellow, depending on the proportions of gold and silver.
The gold content of naturally occurring electrum in modern Western Anatolia ranges from 70% to 90%, in contrast to the 45–55% of gold in electrum used in ancient Lydian coinage of the same geographical area. This suggests that one reason for the invention of coinage in that area was to increase the profits from seigniorage by issuing currency with a lower gold content than the commonly circulating metal. (See also debasement.)
Electrum was used as early as the third millennium BCE in Old Kingdom of Egypt, sometimes as an exterior coating to the pyramidions atop ancient Egyptian pyramids and obelisks. It was also used in the making of ancient drinking vessels. The first metal coins ever made were of electrum and date back to the end of the 7th century or the beginning of the 6th century BCE. For several decades, the medals awarded with the Nobel Prize have been made of gold-plated green gold.
The name "electrum" is the Latinized form of the Greek word ἤλεκτρον (èlektron), mentioned in the Odyssey referring to a metallic substance consisting of gold alloyed with silver. The same word was also used for the substance amber, likely because of the pale yellow colour of certain varieties. It is from amber's electrostatic properties that the modern English words "electron" and "electricity" are derived. Electrum was often referred to as "white gold" in ancient times, but could be more accurately described as "pale gold", as it is usually pale yellow or yellowish-white in colour. The modern use of the term white gold usually concerns gold alloyed with any one or a combination of nickel, silver, platinum and palladium to produce a silver-coloured gold.
Electrum consists primarily of gold and silver but is sometimes found with traces of platinum, copper, and other metals. The name is mostly applied informally to compositions between about 20–80% gold and 20–80% silver atoms, but these are strictly called gold or silver depending on the dominant element. Analysis of the composition of electrum in ancient Greek coinage dating from about 600 BCE shows that the gold content was about 55.5% in the coinage issued by Phocaea. In the early classical period, the gold content of electrum ranged from 46% in Phokaia to 43% in Mytilene. In later coinage from these areas, dating to 326 BCE, the gold content averaged 40% to 41%. In the Hellenistic period, electrum coins with a regularly decreasing proportion of gold were issued by the Carthaginians. In the later Eastern Roman Empire controlled from Constantinople, the purity of the gold coinage was reduced, and an alloy that can be called electrum began to be used.
The earliest known electrum coins, Lydian and East Greek coins found under the Temple of Artemis at Ephesus, are currently dated to the last quarter of the 7th century BCE (625-600 BCE). Electrum is believed to have been used in coins c.600 BCE in Lydia during the reign of Alyattes.
Electrum was much better for coinage than gold, mostly because it was harder and more durable, but also because techniques for refining gold were not widespread at the time. The discrepancy between gold content of electrum from modern Western Anatolia (70–90%) and ancient Lydian coinage (45–55%) suggests that the Lydians had already solved the refining technology for silver and were adding refined silver to the local native electrum some decades before introducing the pure silver coins cited below.
In Lydia, electrum was minted into coins weighing 4.7 grams (0.17 oz), each valued at 1/3 stater (meaning "standard"). Three of these coins—with a weight of about 14.1 grams (0.50 oz))—totalled one stater, about one month's pay for a soldier. To complement the stater, fractions were made: the trite (third), the hekte (sixth), and so forth, including 1/24 of a stater, and even down to 1/48 and 1/96 of a stater. The 1/96 stater was only about 0.14 grams (0.0049 oz) to 0.15 grams (0.0053 oz). Larger denominations, such as a one stater coin, were minted as well.
Because of variation in the composition of electrum, it was difficult to determine the exact worth of each coin. Widespread trading was hampered by this problem, as the intrinsic value of each electrum coin could not be easily determined.
These difficulties were eliminated circa 570 BCE when the Croeseids, coins of pure gold and silver were introduced. However, electrum currency remained common until approximately 350 BCE. The simplest reason for this was that, because of the gold content, one 14.1 gram stater was worth as much as ten 14.1 gram silver pieces.
Electrum coin from Ephesus, 620-600 BC.
Electrum coin from Kyzikos, Mysia, early–mid 4th centuries BC.
Electrum stater, Carthage, circa 300 BCE.
- Corinthian bronze – a highly prized alloy in antiquity, which may have contained electrum
- List of alloys
- Orichalcum – another distinct metal or alloy mentioned in texts from classical antiquity, later used to refer to brass
- Shakudō – a Japanese billon of gold and copper with a dark blue-purple patina
- Shibuichi – another Japanese alloy known for its patina
- Thokcha – an alloy of meteoric iron or "thunderbolt iron" commonly used in Tibet
- Tumbaga – a similar material, originating in Pre-Columbian America
- Chisholm, Hugh, ed. (1911). Encyclopædia Britannica. 9 (11th ed.). Cambridge University Press. p. 252. .
- Kurke, Leslie (1999). Coins, Bodies, Games, and Gold: The Politics of Meaning in Archaic Greece. Princeton University Press. pp. 6–7. ISBN 0691007365.
- Konuk, Koray (2012). Metcalf, William E. (ed.). Asia Minor to the Ionian Revolt. The Oxford Handbook of Greek and Roman Coinage. Oxford University Press. pp. 49–50. ISBN 9780199372188.
- Cahill, Nick; Kroll, John H. New archaic coin finds at Sardis, AJA 109 (2005). pp. 609–614.
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