Spherocobaltite

Spherocobaltite
240px Spherocobaltite from Peramea, Lérida, Catalonia, Spain
General
Category	Carbonate mineral
Formula (repeating unit)	CoCO3
Strunz classification	5.AB.05
Crystal symmetry	Trigonal - hexagonal scalenohedral H-M symbol (3 2/m) Space group: R 3c
Unit cell	a = 4.65, c = 14.95 [Å]; Z = 6
Identification
Formula mass	118.94 g/mol
Color	Pink to red, brown, grey, velvet-black (surface alteration)
Crystal habit	Encrustations - forms crust-like aggregates on matrix, crystals uncommon: rhombohedral to discoidal
Crystal system	Trigonal
Cleavage	Perfect rhomboidal cleavage
Mohs scale hardness	4
Luster	Vitreous
Streak	Pink
Diaphaneity	Transparent to translucent
Specific gravity	4.13
Optical properties	Uniaxial (–)
Refractive index	nε = 1.600, nω = 1.885
Birefringence	0.285
Pleochroism	Dichroic: O = violet-red; E = rose-red
References

Spherocobaltite or sphaerocobaltite is a cobalt carbonate mineral with chemical composition CoCO₃. In its (rare) pure form, it is typically a rose-red color, but impure specimens can be shades of pink to pale brown. It crystallizes in the trigonal crystal system.

Discovery and occurrence

Spherocobaltite was first described in 1877 for an occurrence within cobalt and nickel veins in the St. Daniel Mine of the Schneeberg District, Erzgebirge, Saxony, Germany. The name is from the Greek "sphaira", sphere, and cobalt, in reference to its typical crystal habit and composition. It occurs within hydrothermal cobalt-bearing mineral deposits as a rare phase associated with roselite, erythrite, annabergite and cobalt rich calcite and dolomite.

File:Spherocobaltite-260478.jpg

Cluster of spherocobaltite crystals from the Katanga Copper Crescent, Katanga (Shaba), Democratic Republic of Congo (size: 11.5 x 6.0 x 4.5 cm)

Further reading

• Sphärocobaltit