Spherocobaltite

(repeating unit)CoCO₃IMA symbolScbt^[1]Strunz classification5.AB.05Crystal systemTrigonalCrystal classHexagonal scalenohedral (3m)
H-M symbol: (3 2/m)Space groupR3cUnit cella = 4.65, c = 14.95 [Å]; Z = 6IdentificationFormula mass118.94 g/molColorMost commonly dark magenta red; pink to red, brown, brownish red, grey, greyish red, velvet-black (due to surface alteration)Crystal habitEncrustations - forms crust-like aggregates on matrix, crystals uncommon: rhombohedral to discoidalCleavagePerfect rhomboidal cleavage ^[2]Mohs scale hardness4LusterVitreousStreakPinkDiaphaneityTransparent to translucentSpecific gravity4.13Optical propertiesUniaxial (–)Refractive indexn_ε = 1.600, n_ω = 1.885Birefringence0.285PleochroismDichroic: O = violet-red; E = rose-redReferences^[2][3][4]

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, Ore Mountains, Saxony, Germany. The name is from the Greek "sphaira", sphere, and cobalt, in reference to its typical crystal habit and composition.^[2] It occurs within hydrothermal cobalt-bearing mineral deposits as a rare phase associated with roselite, erythrite, annabergite and cobalt rich calcite and dolomite.^[4]

References

Further reading

• Sphärocobaltit