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The tetrahedrite Mineral Series

Lustrous Tetrahedrite with Pyrite

The Tetrahedrite series is composed of two member minerals: Tetrahedrite, the antimony-rich end member, and Tennantite, the arsenic-rich end member. Tetrahedrite is the more common member of this series, and is also the most common sulfosalt mineral. This page discusses Tetrahedrite; Tennantite has its own dedicated page. The most common crystal habit for Tetrahedrite is tetrahedral, which describes an unusual triangular crystal form. Its name is derived from this interesting crystal shape. 

Chemical Formula

Cu12Sb4S13

Color

Steel Gray to black. May also be iridescent with a colorful metallic film or with a slightly bronze color.

Crystal System

Isometric

Properties

Streak
Reddish-brown, dark gray, black
Hardness
3 - 4
Transparency
Opaque
Specific Gravity
4.6 - 5.1
Luster
Metallic
Cleavage
None
Fracture
Subconchoidal
Tenacity
Brittle

Crystal Habits

In tetrahedral and tristetrahedral crystals and clusters, resembling pyramids. Crystals are usually well-formed and very distinct. Less commonly in dodecahedral or combination dodecahedral-tetrahedral crystals. Also in ball-shaped formations, rosettes, grainy and massive. Crystals may be deeply striated in a triangular pattern, and may also be intergrown.

3D Crystal Atlas

Additional Information

Composition
Copper antimony sulfide, with some arsenic replacing the antimony. Iron and zinc variably substitute the copper up to 15 percent.
In Group
Sulfides; Sulfosalts
Striking Features
Unique crystal structure and lack of cleavage
Environment
In low to moderate grade hydrothermal and epithermal vein deposits, and in contact metamorphic deposits. 
Rock Type
Sedimentary, Metamorphic

Other Names

Fahlerz Old German term for Tetrahedrite, describing it as ashen-colored ore. The name is in reference to its lack of yellow or copper hue and application as a copper ore.

Varieties

 -   Old name for a mercury-rich variety of Tetrahedrite, named for the type locality of Schwaz in Austria where this variety has been found. 

Uses

Tetrahedrite is an ore of copper.

Noteworthy Localities

Several classic European localities have produced exceptional examples of Tetrahedrite. These include Freiberg, Saxony, Germany; Siegerland, North Rhine-Westphalia, Germany; the Ste Marie-aux-Mines, Haut-Rhin, Alsace, France; Příbram, Bohemia, Czech Republic; and Cavnic (Kapnic), Maramureș Co., Romania. A mercury-rich variety of Tetrahedrite is well-known from the Schwazz-Brixlegg area, Inn valley, North Tyrol, Austria. The famous Herodsfoot Mine of Lanreath, Liskeard District, Cornwall, England, has produced excellent crystals of this mineral, almost always associated with golden Chalcopyrite.

Peru has produced what many believe are among the finest Tetrahedrite crystals, in a wide range of different localities. These include Casapalca, Lima Department; the Mundo Nuevo Mine, Huamachuco, La Libertad Department; the Pasto Bueno and Pachapaqui Districts, Ancash Department; the Julcani Mine, Huancavelica Department; the Huallanca District, Huánuco Department; and the Alimon Mine, Huaron, Pasco department. Another important South American locality is the Machacamarca District, Potosí Department, Bolivia.

In Mexico, large Tetrahedrite crystal clusters have come from Zacatecas at Concepción del Oro and at San Martín. In the U.S., an important locality was the Bingham Canyon Mine, Salt Lake Co., Utah. Lustrous Tetrahedrite and Pyrite associations were found in the Daly-Judge Mine, Park City District, Wasatch Mts, Summit Co., Utah; and Tetrahedrite was one of the important accessory minerals found with Rhodochrosite at the Sweet Home Mine, Alma, Park Co., Colorado.

Distingushing Similar Minerals

Tennantite - Very difficult to distinguish without complex tests, although certain localities are indicative of Tennantite, and Tennantite generally doesn't form as sharp crystals as Tetrahedrite.
Enargite - Different crystal habits.
Sphalerite - Has perfect cleavage, and and may exhibit transparency (whereas Tetrahedrite is never transparent.)


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