Stibnite

cinnabar

galena

Formula: Sb2S3
Sulphide, antimony mineral
Specific gravity: 4.6 to 4.7
Hardness: 2
Streak: Dark grey
Colour: Lead-grey
Solubility: Moderately soluble in hydrochloric acid; slightly soluble in nitric acid
Melting point: 546oC
Environments:

Hot spring deposits
Hydrothermal environments common

Stibnite is found in epithermal (low temperature) hydrothermal veins, particularly in stibnite- quartz veins, in replacement deposits and in hot spring deposits. It is associated with other antimony minerals that have formed as the product of its decomposition, and with galena, cinnabar, sphalerite, baryte, realgar, orpiment and gold.

At Schemnitz, Slovakia, stibnite occurs with stibiconite (FM OP33).

Alteration

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

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)

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

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