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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. Electrum was used as early as the third millennium BC in Old Kingdom Egypt, sometimes as an exterior coating to the pyramidions atop ancient Egyptian pyramids and obelisks. Electrum 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 BC. For several decades the medals awarded with the Nobel Prize have been made of gold-plated green gold. The name electrum was also used to denote German ‘silver’, mainly for its use in making technical instruments.〔(Discussion about the use of terms ‘Electrum’, ‘German silver’, and ‘Nickel silver’ for drawing instruments. )〕 ==Composition== 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 BC 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 BC, 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「electrum」の詳細全文を読む スポンサード リンク
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