Electrum

electrum

Natural or artificial alloy of gold with at least 20% silver, used to make the first known coins in the Western world. Most natural electrum also contains copper, iron, palladium, bismuth, and perhaps other metals. The colour varies from white-gold to brassy, depending on the percentages of the major constituents and copper. The first Western coinage, possibly begun by King Gyges of Lydia (7th century BC), consisted of irregular ingots of electrum bearing his stamp as a guarantee of negotiability at a predetermined value. See also coinage.

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electrum [i′lek·trəm]

(metallurgy)

A naturally occurring alloy of gold and silver.

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electrum

A natural alloy of gold and silver, sometimes employed in the decorations of ancient temples and palaces.

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Electrum 

a mineral, a type of native gold with a silver content above 25–50 percent.

Electrum, which contains admixtures of tellurium, copper, antimony, and mercury, is characterized by nonuniform distribution (zonality, decomposition structures of high-silver solid solutions of gold). It crystallizes in the isometric system. It rarely occurs in the form of crystals, usually being encountered in the form of flat dendrites, ranging in area from fractions of 1 mm² to 10–20 mm² (sometimes reaching 30–50 mm²), or in the form of irregular microscopic particles. Electrum nuggets weighing as much as 400 g have been found. The color ranges from gold yellow to light yellow, depending on the silver content. The hardness on Mohs’ scale is 2–3, and the density ranges from 1,500 to 1,650 kg/m³.

Electrum, a relatively rare mineral, is encountered in hydro-thermal deposits and quartz and chalcedony-quartz veins in association with carbonates, adularias, sulfides, tellurides, and sulfo salts of silver, lead, and antimony. The smallest inclusion of electrum establishes the gold content of copper pyrite and complex ores. Electrum is a component of gold ores.

REFERENCE

Petrovskaia, N. V. Samorodnoe zoloto. Moscow, 1973.