Chemistry

Electrum, The Prize of the Ancients and the Lure of Modern Gold Miners



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The word “electrum” has invaded modern language. We see it pop up in such diverse places as the Star Wars universe, numerous fantasy games, and occasionally in a scientific context. Given the awareness of the word it might be surprising that there is just a vague understanding of what the material behind the word actually is. Is it a new metal all its own? No, not actually. The earliest refined examples of the material come from preserved ancient coins from Miletus dated between 610 and 560 BC. The material itself came from the Pactolus River which was controlled by the kingdom of Lydia. The people of Lydia are thought to have been early to capitalize on the profits of being merchants and moving from agriculture to urban culture and from barter to coin economy.


Electrum is an alloy. It naturally occurs in the riverbed of the Pactolus River (which natively carries between 70 and 90 percent gold) and other areas of the world. Modern sources include the tertiary andesitic gold fields in the Americas, Hungary, and New Zealand. The coins of the region have been tested to be an average of 53 percent gold, so the state was adding silver and copper to the official alloy. There are some variations among different professions as to what electrum is in a modern sense. It has been called “white gold” by some or “nickel silver” by others. Modern standards consider alloys of the material to be electrum if they possess 20% or more silver along with gold, copper, platinum, nickel, or zinc depending on the source referred to. Since the Greek root word also applies to Amber, many times ancient Electrum was more brassy colored than gold largely in part to the addition of copper for coloration, durability, and wear. In appearance the material maintains a metallic luster, and has the malleability of gold.


Before it was used for coins it also found use as a decorative element. Ancient Egyptians used it to plate their pyramidions or capstone of their pyramids and obelisks. It found use in jewelry and as part of writing instruments and eating utensils that were subjected to high wear. The gold blended with silver prevented tarnishing making white-gold versions of electrum highly sought after for both religious icons and personal adornment. Gold and silver alone were considered too soft to be used pure. Copper and lead were both easily incorporated into metal alloys with gold and silver. While it does occur naturally, both in Turkey and in the Americas, ancient people found it easy enough to make the alloy artificially. One should note that modern white-gold is palladium, nickel, and silver making it and modern electrum very different creations.


When looking at modern electrum most people see a gold-bearing ore with at least 20% silver by weight. The pale golden color can sometimes have a greenish tinge if copper is present. The streak made by an electrum nugget will match the color of the metal. Both hardness and density varies based on the silver content. Similar to lead, nuggets of the material can be cut with a knife and they are easily formed into other shapes. While electrum can be enjoyed on its own and comes from many places that have a high silver concentration often times it is used as a gold ore and processed to separate the metals contained in it. At least one expert estimates that a good percentage of “native gold” found as free nuggets from epithermal deposits is actually electrum.

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ARTICLE SOURCES AND CITATIONS
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