Electrum Metal Alloy
Electrum is a naturally occurring alloy of gold and silver with a small amount of other metals. The man-made alloy of gold and silver is chemically similar to electrum but usually is called green gold.
Electrum Chemical Composition
Electrum consists of gold and silver, often with small amounts of copper, platinum, or other metals. Copper, iron, bismuth, and palladium commonly occur in natural electrum. The name may be applied to any gold-silver alloy that is 20-80% gold and 20-80% silver, but unless it is the natural alloy, the synthesized metal is more correctly termed ‘green gold’, ‘gold’, or ‘silver’ (depending which metal is present in the higher amount). The ratio of gold to silver in natural electrum varies according to its source. Natural electrum found today in Western Anatolia contains 70% to 90% gold. Most examples of ancient electrum are coins, which contain increasingly lower amounts of gold, so it’s believed the raw material was alloyed further to conserve profit.
The word electrum has also been applied to the alloy called German silver, although this is an alloy that is silver in color, not elemental composition. German silver typically consists of 60% copper, 20% nickel and 20% zinc.
Natural electrum ranges in color from pale gold to bright gold, depending on the amount of the element gold present in the alloy. Brassy-colored electrum contains a higher amount of copper. Although the ancient Greeks called the metal white gold, the modern meaning of the phrase “white gold” refers to a different alloy that contains gold but appears silvery or white. Modern green gold, consisting of gold and silver, actually does appear yellowish -green. Intentional addition of cadmium may enhance the green color, although cadmium is toxic, so this limits the uses of the alloy. The addition of 2% cadmium produces a light green color, while 4% cadmium yields a deep green color. Alloying with copper deepens the color of the metal.
The exact properties of electrum depend on the metals in the alloy and their percentage. Generally, electrum has a high reflectivity, is an excellent conductor of heat and electricity, is ductile and malleable, and is fairly corrosion resistant.
Electrum has been used as currency, to make jewelry and ornaments, for drinking vessels, and as an exterior coating for pyramids and obelisks. The earliest known coins in the Western world were minted of electrum and it remained popular for coinage until about 350 BC. Electrum is harder and more durable than pure gold, plus the techniques for gold refining were not widely known in ancient times. Thus, electrum was a popular and valued precious metal.
As a natural metal, electrum was obtained and used by early man. Electrum was used to make the earliest metal coins, dating back at least to the 3rd millennium BC in Egypt. The Egyptians also used the metal to coat important structures. Ancient drinking vessels were made of electrum. The modern Nobel Prize medal consists of green gold (synthesized electrum) plated with gold.
Where Can You Find Electrum?
Unless you visit a museum or win the Nobel Prize, you best chance of finding electrum is to seek the natural alloy. In ancient times, the chief source of electrum was Lydia, around the Pactolus River, a tributary of the Hermus, now called the Gediz Nehriin in Turkey. In the modern world, the primary source of electrum is Anatolia. Smaller amounts also may be found in Nevada, in the USA.