Stibnite

stibnite

cinnabar

antimony

galena

Images

Formula: Sb2S3
Sulphide, stibnite group, antimony-bearing mineral
Crystal System: Orthorhombic
Specific gravity: 4.63 measured, 4.625 calculated
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.

Localities

At the Xikuangshan Sb deposit, Lengshuijiang County, Loudi, Hunan, China, stibnite occurs as lustrous, metallic crystals, sometimes as large aggregates (AESS).
Stibnite from Xikuangshan - Image

At the Wuning Mine, Qingjiang, Wuning county, Jiujiang, Jiangxi, China, some of the largest and finest specimens of stibnite have been recovered from the "Cave of Giants" (MinRec 55.3.274-277).
Stibnite from Wuning - Image

The Ichinokawa Mine, Saijo City, Ehime Prefecture, Japan, is famous for its marvelous stibnite specimens, now found in museums around the world. The best specimens were found in the late 19th century, during peak productivity of the mine, but it closed in 1962.
(Mindat).
The mines at Ichinokawa straddle a major fault system marking the boundary between the Cretaceous (143 to 66 million years ago) Izumi sandstones and conglomerates and the Sanbagawa metamorphosed series of graphite schist and black phyllite schists. Stibnite occurs as lodes in quartz veins cutting across the graphite-rich schists, overlain by conglomerate.
The Ichinokawa mine is a typical vein-type fissure-filled deposit. Hydrothermal fluids containing antimony rose along the weak points and along the fissures of the fault, depositing veins of stibnite and quartz. All of the veins are embedded in black schist and conglomerate layers.
Stibnite is often accompanied by quartz. Small amounts of pyrite and arsenopyrite are also seen. Crystal pockets developed within the veins, and acicular to columnar stibnite crystals were often seen among scattered quartz crystals. Large crystal-lined pockets could reach from 10 cm to over 1 metre in length, and the beautiful stibnite crystals obtained from these cavities are prized by collectors and museums around the world. In general, the shallower orebodies were the ones containing open voids with the best stibnite crystals, whereas the deeper deposits were more likely to yield dense, compact, massive stibnite. The most noteworthy feature of the Ichinokawa mine veins was the presence of “crystal caves” in which gigantic stibnite crystals had grown (MinRec 56.2.141-188).
Stibnite from the Ichinokawa Mine - Image

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

At Wet Swine Gill, Coombe Height, Caldbeck, Allerdale, Cumbria, England, UK, stibnite occurs as tiny glittery silver specks on a quartz matrix, with specks of a yellow mineral that is possibly orpiment (AESS).
Stibnite from Wet Swine Gill - Image

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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