ELECTRUM MINERAL FACTS Nevada Turquoise gem stones
The Gem and Mineral Collector's Photo Gallery by Nevada Outback


Electrum Mineral Facts:

Chemical Formula: Au(Ag) Gold and Silver alloy, more than 20% silver by weight.

Colors: Pale metallic gold, streak is the same.

Hardness: 2.5 to 3

Density: 12.5 to 15.5
The density is variable depending on the silver content. 

Cleavage: Electrum is ductile and mallable. Also sectile, and can be cut with a knife like lead.

Crystallography: Isometric, commonly octahedral.
Usually in irregular plates, scales or masses, and seldom definitely crystallized.

Luster:. Metallic luster.

Optics: (Refractive Index):  Opaque

Nevada Electrum, Tuscarora, Elko Co.

Nevada Electrum, Tuscarora District

Composition, Structure and Associated Minerals:
Electrum is composed of an exceedingly intimate mixture (an isomorphous solid solution) of gold and silver. It is a natural alloy of the two metals.

The electrum known to Pliny the ancient Roman historian was probably named on account of its yellow color, from the Greek word for amber, of Strabo. It was defined as a natural alloy containing one-fifth of silver. The term is occasionally used by modern writers to cover natural gold-silver alloys, but has not met with general acceptance, its place being supplied by an extension of the term "gold." Electrum is derived almost entirely from the Tertiary andesitic goldfields of North, South, and Central America, New Zealand, and Hungary. Its color varies, with the percentage of silver present, from yellowish white to pale yellow.

Electrum is more commonly found in gold deposits with a high silver content, and is typically found in epithermal type deposits.  Here the gold is still associated with the metallic impurities of the sulfur bearing waters in which it has made its ascent towards the surface. Because of this, it is associated with silver minerals such as the ruby silvers, stephanite and other silver minerals as well as other sulfides such as galena.

Identification and Diagnostics
Electrum meets all the standard tests for metallic, native gold, but contains a much higher than normal silver content. It is usually distinguished by its pale golden color which is much lighter than typically seen in native gold. Factual confirmation requires a chemical analysis of the sample.

Nevada Electrum

Round Mountain, Nevada Electrum

Occurrence, Localities and Origins:
Epithermal ore deposits form at shallow depth and are often associated with comparatively young volcanic rocks . Electrum has been found in epithermal gold-silver deposits of both high- and low-sulfidation styles. Electrum is found in silver-gold epithermal vein systems associated with silver and other sulfides  in many bonanza type silver mining districts. In Nevada it is an important ore at  the Comstock lode, Tonopah and at Round Mountain (where it is still actively mined). It is found with the rich silver ores of  Mexico, Chile, Bolivia and Peru. 

In Europe it is known from several  localities in Hungary where the deposits are associated with Eocene volcanic rocks. It is also found in epithermal deposits in New Zealand. Probably an unrecognized but significant amount of the free gold recovered from many epithermal deposits is actually electrum. In either case, it is an important ore of gold.

Return to the Mineral Collectors Information Page



Please note that the author, Chris Ralph, retains all copyrights to this entire document and it may not be reproduced, quoted or copied without permission.

Turq_nev_6b.gif (5020 bytes)


Nevada Outback Gems

Find out more by checking out All of our links below:


View our Contemporary Turquoise Jewelry - Wearable Artwork! View our Unique Gem Quality Turquoise Cabochons
Premium Jewelry, with Gemstones of all types Top Quality Loose Gemstones - Gemstones of all types
Rare Crystals and Gemstone Rough, all types Our Free Colored Gemstone Information Encyclopedia
Chris' Gold Prospecting Encyclopedia Take a virtual tour of our Nevada Turquoise mines
Miners Reference Pages         California Gold Rush Stories More Info about Turquoise, the Beautiful Gem
Metal Detecting with the MXT Metal Detector Nevada Outback Gems Homepage
Build Your Own Mining Equipment Investing in Gold and Precious Metals
Basic Placer Mining More information about us - Nevada Outback Gems
Locations to Prospect for Gold The Rockhound's Corner Nevada Outback Library and Bookstore - Learn more!
Chris's Prospecting Adventures About Nevada Turquoise More Info about Gem Cutting Tanzanite Jewelry
Nevada Outback Gems Site Map Make Your Own Jewelry Buy Safely on EBay: avoid fraud and scam artists