berthierite

antimony

stibnite

arsenopyrite

Berthierite

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Formula: FeSb₂S₄
Sulphosalt, berthierite group, antimony-bearing mineral
Specific gravity: 4.64
Hardness: 2 to 3
Streak: Dark brownish-grey
Colour: Dark steel-grey, often with iridescent tarnish
Common impurities: Mn,Cu,Pb,Ag
Environments:

Hydrothermal environments

Berthierite occurs in low-temperature hydrothermal antimony veins, in portions deficient in sulphur (Webmin, HOM), associated with stibnite, arsenopyrite, pyrite, baryte, calcite, quartz and jamesonite (HOM, Mindat, MW).

The type locality is Chazelles-Haut, Mercoeur, Haute-Loire, Auvergne-Rhône-Alpes, France.

At Baia Marie, Maramures, Romania, fine crystals of berthierite have been found intermixed with stibnite and associated with boulangerite (Minrec 38.3.219).

Alteration

stibnite and pyrite to berthierite and sulphur
Sb₂S₃ + FeS₂ → FeSb2S4 + l/2S₂
(CM 28.725-738)

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

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