Tetrahedrite

tetrahedrite

chalcopyrite

stibnite

skinnerite

Images

Formula: Cu₆[Cu₄(Fe,Zn)₂]Sb₄S₁₃
"Tetrahedrite" was discredited as a species in 2019, and the name now refers to five minerals:
tetrahedrite-(Fe): Cu₆(Cu₄Fe₂)Sb₄S₁₃
tetrahedrite-(Hg): Cu₆(Cu₄Hg₂)Sb₄S₁₃
tetrahedrite-(Mn): Cu₆(Cu₄Mn₂)Sb₄S₁₃
tetrahedrite-(Ni): Cu₆(Cu₄Ni₂)Sb₄S₁₃
tetrahedrite-(Zn): Cu₆(Cu₄Zn₂)Sb₄S₁₃
Sulphosalts, tetrahedrite group
Specific gravity: 4.6 to 5.2
Hardness: 3 to 4
Streak: Black
Colour: Steel grey to iron black
Solubility: Slightly soluble in nitric acid
Common impurities: Ag,Pb,Zn,Fe,As
Environments:

Pegmatites (rare)
Metamorphic environments
Hydrothermal environments (usual)

Tetrahedrite usually occurs in epithermal (low temperature) to mesothermal (moderate temperature) hydrothermal veins, rarely in pegmatites, and also in some contact metamorphic deposits of low to medium temperatute of formation. Associated minerals include chalcopyrite, galena, sphalerite, pyrite, bornite, acanthite, calcite, dolomite, siderite, baryte, fluorite and quartz (HOM).

Localities

At the Huanzala Mine, Huanzala, Huallanca District, Bolognesi Province, Ancash, Peru, specimens have been found with plates of white calcite mixed with massive black tetrahedrite, all completely covered by interlocked crystals of tetrahedrite, galena and fluorite. The galena appears as sharp, skeletal crystals to 2 cm, and the fluorite as colourless, transparent, stepped octahedrons up to 2 cm in size, but the most specracular mineral is the tetrahedrite, which forms razor-sharp, lightly striated, brilliant metallic black tetrahedral crystals to more than 2 cm in size (MinRec 55.1.86).

Tetrahedrite from Huanzala - Image

From Herodsfoot Mine, Lanreath, Cornwall, England, UK, specimen BM.1964,R1021 from the Natural History Museum, London, Features dull metallic grey tetrahedrite crystals with tristetrahedral modifications and an overgrowth of bright brassy chalcopyrite, richly covering a matrix of milky quartz veinstone (RES2).

Tetrahedrite from Herodsfoot Mine - Image

At Redruth, Cornwall, England, UK, tetrahedrite has been found with chalcopyrite and calcite (FM 47545).

At the Eagle Crag Mine, Patterdale, Eden, Cumbria, England, UK, sharp crystals of tetrahedite to 3 mm in size have been found on a quartz matrix (AESS).

Tetrahedrite from Eagle Crag - Image

At the Magma mine, Pioneer District, Pinal county, Arizona, USA, tetrahedrite has been found associated with quartz (R&M 95.1.88).

Alteration

chalcopyrite, stibnite and sulphur to Fe-tetrahedrite and pyrite
10 CuFeS₂ + 2 Sb₂S₃ + 3/2 S₂ → Cu₁₀Fe₂As₄S₁₃ + 8FeS₂
(CM 28.725-738)

skinnerite and sphalerite = Zn-tetrahedrite and chalcocite
4Cu₃SbS₃ + 2ZnS → Cu₁₀Zn₂Sb₄S₁₃ + Cu₂S
(CM 28.725-738)

Fe-tetrahedrite, berthierite and sulphur to chalcopyrite and stibnite
Cu₁₀Fe₂Sb₄S₁₃ + 2FeSb₂S₄ + 11/2S₂ → 10CuFeS₂ + 4Sb₂S₃
(CM 28.725-738)

Fe-tetrahedrite, siderite and sulphur to chalcopyrite, stibnite, CO₂ and O₂
Cu₁₀Fe₂Sb₄S₁₃ + 8Fe(CO₃) + 13/2S₂ → 10CuFeS₂ + 2Sb₂S₃ + 8CO₂ + 4O₂
(CM 28.725-738)

Zn-tetrahedrite to chalcocite, antimony, sphalerite and sulphur
Cu₁₀Zn₂Sb₄S₁₃ → 5Cu₂S + 4Sb + 2ZnS + 3S₂
(CM 28.725-738)

tetrahedrite antimony, sphalerite and sulphur
3Cu₁₀Zn₂Sb₄S₁₃ → 10Cu₃SbS₃ + 2Sb + 6ZnS + 3/2S₂
(CM 28.725-738)

tetrahedrite stibnite and sphalerite
3Cu₁₀Zn₂Sb₄S₁₃ → 10Cu₃SbS₃ + Sb₂S₃ + 6ZnS
(CM 28.725-738)

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