تتراهيدريت

Tetrahedrite
Tetrahedrite crystal with traces of quartz (in middle) and micro mimetite, specimen size 3.5 × 2.5 × 2.5 cm
العامة
التصنيف	Sulfosalt mineral
الصيغة (repeating unit)	(Cu,Fe) 12Sb 4S 13
تصنيف سترونز	2.GB.05
النظام البلوري	Cubic
Crystal class	Hextetrahedral (43m) H-M symbol: (4 3m)
Space group	I43m
Unit cell	a = 10.39(16) Å; Z = 2
التعرف
Color	Steel gray to iron-gray
Crystal habit	Groups of tetrahedral crystals; massive, coarse to fine compact granular
Twinning	Contact and penetration twins on {111}
Cleavage	None
Fracture	Uneven to subconchoidal
Tenacity	Somewhat brittle
Mohs scale hardness	3+1⁄2 – 4
Luster	Metallic, commonly splendent
Streak	Black, brown to dark red
Diaphaneity	Opaque, except in very thin fragments
الجاذبية النوعية	4.97
الصفات البصرية	Isotropic
Refractive index	n greater than 2.72
References

Tetrahedrite is a copper antimony sulfosalt mineral with formula: (Cu,Fe) 12Sb 4S 13. It is the antimony endmember of the continuous solid solution series with arsenic-bearing tennantite. Pure endmembers of the series are seldom if ever seen in nature. Of the two, the antimony rich phase is more common. Other elements also substitute in the structure, most notably iron and zinc, along with less common silver, mercury and lead. Bismuth also substitutes for the antimony site and bismuthian tetrahedrite or annivite is a recognized variety. The related, silver dominant, mineral species freibergite, although rare, is notable in that it can contain up to 18% silver.

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 علم المعادن

Tetrahedrite gets its name from the distinctive tetrahedron shaped cubic crystals. The mineral usually occurs in massive form, it is a steel gray to black metallic mineral with Mohs hardness of 3.5 to 4 and specific gravity of 4.6 to 5.2.

Tetrahedrite occurs in low to moderate temperature hydrothermal veins and in some contact metamorphic deposits. It is a minor ore of copper and associated metals. It was first described in 1845 for occurrences in Freiberg, Saxony, Germany. Historically, it was an important ore of copper, the formula Cu₃SbS₃ corresponding with 57.5% of the metal; it was also worked as an ore of silver, of which element it sometimes contains as much as 30%.

 تطبيقات

The now-defunct company Alphabet Energy announced plans to offer a thermoelectric device based on tetrahedrite to turn heat into electricity. The company claimed that other thermoelectrics typically produce about 2.5 percent efficiency, while tetrahedrite could achieve 5 to 10 percent.

Other thermoelectrics are either scarce, expensive ($24–146/kg vs $4 for tetrahedrite) and/or toxic. Working with a natural material also reduces manufacturing costs.

 صور

• 

  Tetrahedrite crystals with chalcopyrite and sphalerite from the Casapalca Mine, Peru (size: 8.2 x 6.4 x 4.7 cm)

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  Tetrahedrite from Casapalca Mine, Casapalca, Huarochiri Province, Lima Department, Peru

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  Rhodochrosite with fluorite, tetrahedrite and quartz; the tetrahedrite occurs as sharp, metallic crystals

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  Tetrahedrite crystals to several inches on size in combination with quartz crystals

 انظر أيضاً

• بورنيت
• كوپريت
• قائمة المعادن

 وصلات خارجية

• Media related to تتراهيدريت at Wikimedia Commons
• Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., Wiley, ISBN 0-471-80580-7
• Mineral galleries
• Webmineral data