Stannite

Stannite
Stannite Fabulosa Mine, Larecaja Province, La Paz Department, Bolivia- 2 mm crystals
General
Category	Sulfide mineral
Formula (repeating unit)	Cu2FeSnS4
Strunz classification	2.CB.15a
Crystal system	Tetragonal
Crystal class	Scalenohedral (42m) H-M symbol: (4 2m)
Space group	I42m
Unit cell	a = 5.4432, c = 10.7299 [Å]; Z = 2
Identification
Color	Steel-gray to iron-black, may tarnish blue
Crystal habit	Rarely as pseudo-octahedral crystals also massive, granular, and disseminated
Twinning	Penetration twins on {102}
Cleavage	Indistinct on {110} and {001}
Fracture	Uneven
Mohs scale hardness	4
Luster	Metallic
Streak	Black
Diaphaneity	Opaque
Specific gravity	4.3 - 4.5
References

Stannite is a mineral, a sulfide of copper, iron, and tin.

The chemical formula Cu₂FeSnS₄. Zinc commonly occurs with the iron and trace germanium may be present. Stannite is used as an ore of tin, consisting of approximately 28% tin, 13% iron, 30% copper, 30% sulfur by mass. It is found in tin-bearing, hydrothermal vein deposits occurring with chalcopyrite, sphalerite, tetrahedrite, arsenopyrite, pyrite, cassiterite, and wolframite.

It is also known as bell metal ore as tin is an important constituent of bell-metal. It is thought the exploitation of tin deposits in Cornwall led to an expansion in bell founding.

The name comes from the Latin for tin: stannum. It was first described in 1797 for an occurrence in Wheal Rock, St. Agnes, Cornwall, England.