Alabandite

Alabandite
Group of octahedral alabandite crystals partially coated with pink rhodochrosite, from Uchucchacua Mine, Oyon, Lima, Peru (size: 60 mm x 59 mm x 46 mm, 204 g)
General
Category	Sulfide mineral
Formula (repeating unit)	MnS
Strunz classification	2.CD.10 (10 ed) II/C.15-30 (8 ed)
Dana classification	2.8.1.4
Crystal system	Cubic
Crystal class	Hexoctahedral (m3m) H-M symbol: (4/m 3 2/m)
Space group	Fm3m
Unit cell	a = 5.2236 Å; Z = 4
Identification
Color	black, steelgray, brownish-black
Crystal habit	mostly massive or granular; cubic or octahedral crystals to 1 cm
Twinning	Lamellar || {111}
Cleavage	Perfect on {100}
Fracture	Irregular, uneven
Tenacity	Brittle
Mohs scale hardness	3.5 to 4
Luster	Sub-metallic
Streak	Green
Diaphaneity	Opaque, translucent in thin fragments
Specific gravity	4.053
Optical properties	Isotropic
Refractive index	n = 2.70
References

Alabandite or alabandine is a rarely occurring manganese sulfide mineral. It crystallizes in the cubic crystal system with the chemical composition Mn²⁺S and develops commonly massive to granular aggregates, but rarely also cubic or octahedral crystals to 1 cm.

Alabandite was first described in 1784 by Franz-Joseph Müller von Reichenstein. The mineral name is derived from its supposed discovery locality at Alabanda (Aïdin) in Turkey.

Alabandite forms in epithermal polymetallic sulfide veins and low-temperature manganese deposits. It occurs with acanthite, calcite, chalcopyrite, galena, pyrite, quartz, rhodochrosite, rhodonite, sphalerite and native tellurium. Sometimes it was found in meteorites.

Localities are several areas in Antarctica, Argentina, Armenia, Australia, Bolivia, Brazil, Bulgaria, Canada, China, Czech Republic, Finland, France, Germany, Ghana, Greece, Greenland, India, Italy, Japan, Kyrgyzstan, Mexico, New Zealand, Norway, Peru, Poland, Romania, Russia, Slovakia, South Africa, South Korea, Sweden, Switzerland, Taiwan, Tanzania, the United Kingdom, the US, Uzbekistan and Yemen. Altogether at present time approximately 220 discovery sites are registered.

Alabandite crystallizes in the cubic crystal system in the space group Fm3m with the lattice parameter a = 5.22 Å and four formula units per unit cell.