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Sylvanite Coating on Quartz

The Mineral sylvanite

Sylvanite is a unique mineral that forms with both gold and silver in its structure. Sylvanite is structurally similar to Calaverite, but it contains silver in its structure in addition to gold. If less than 13.4% of silver is replaced by gold, it is no longer classified as Sylvanite, but rather Calaverite. 

The name Sylvanite is derived from sylvanium, which was an original name proposed for the element tellurium. Tellurium is present within Sylvanite, and its first documented occurrence was in the Transylvania region of Romania - hence the name sylvanium.
Chemical Formula (Au,Ag)Te4
Composition Telluride of gold and silver 
Color Silver-white, whitish-yellow, gray
Streak Dark gray to black
Hardness 1.5 - 2
Crystal System Monoclinic
3D Crystal Atlas
(Click for animated model) 
Crystal Forms
and Aggregates
In prismatic, bladed, and columnar crystals. Also grainy, massive, encrusting, in veins, and in dendritic formations. Crystals may be deeply striated or have hopper and skeletal growths.
Transparency Opaque
Specific Gravity 7.9 - 8.3
Luster Metallic
Cleavage 1,1
Fracture Uneven
Tenacity Brittle
In Group Sulfides; Tellurides
Striking Features Color, crystal habits, and mode of occurrence
Environment Low temperature hydrothermal replacement deposits.
Rock Type Sedimentary
Popularity (1-4) 3
Prevalence (1-3) 3
Demand (1-3) 1

Sylvanite AUCTIONS

Sylvanite is an ore of gold and silver. It is also rare collector's mineral, with special value due to its gold content.

Veins and dendritic growths of Sylvanite , some with patterns, come from the Transylvania in Romania at Baia de Arieş (Offenbánya), Alba Co.; and Sacarîmb (Nagyág), Hunedoara Co. Elongated crystals often with deep striations or skeletal/hoppered growths are highly regarded from the Emperor Mine, Vatukoula, Viti Levu, Fiji. 

There are several important Colorado localities of Sylvanite; most notable is the Cripple Creek District, Teller Co., Colorado. Other Colorado localities include the Keystone Mine, Magnolia District, Boulder Co.; the Jamestown District, Boulder Co., and the Bessie G Mine, La Plata Co., Colorado.

Quartz, Fluorite, Calcite, Calaverite, Pyrite, Tellurium

Calaverite - May be very similar, though Calaverite lacks cleavage, and is also greater in hardness.

sylvanite PHOTOS
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