Manganosite

Manganosite
Black manganosite crystals with zincite and sonolite
General
Category	Oxide mineral
Formula (repeating unit)	Manganese oxide, MnO
IMA symbol	Mng
Strunz classification	4.AB.25
Crystal system	Cubic
Crystal class	Hexoctahedral (m3m) H-M symbol: (4/m 3 2/m)
Space group	Fm3m
Unit cell	a = 4.44 Å; Z = 4
Identification
Color	Emerald-green, becoming black on exposure to air
Crystal habit	Granular to massive; Octahedral crystals uncommon
Cleavage	Perfect on [100], [010] and [001]
Fracture	Fibrous
Mohs scale hardness	5–6
Luster	Vitreous, adamantine to dull
Streak	Brown
Diaphaneity	Transparent to translucent
Specific gravity	5.364
Optical properties	Isotropic
Refractive index	n = 2.16–2.17
References

Manganosite is a rare mineral composed of manganese(II) oxide MnO. It was first described in 1817 for an occurrence in the Harz Mountains, Saxony-Anhalt, Germany. It has also been reported from Langban and Nordmark, Sweden and at Franklin Furnace, New Jersey. It also occurs in Japan, Kyrgyzstan and Burkina Faso.

It occurs in manganese nodules. It also occurs as alteration of manganese minerals such as rhodocrosite during low oxygen metamorphism and metasomatism.