Cobaltoan Calicte is a variety of Calcite containing Co2+ replacing Ca.

Originally described from Vallone stope, Cape Calamita Mine (Calamita Mine), Capoliveri, Elba Island, Livorno Province, Tuscany, Italy.
 
The various crystallized forms of Calcite include masses, grains, stalactites, scalenohedrons (twelve-faced crystals, each face exhibiting three unequal sides), and rhombodedrons (six-faced crystals, each face the shape of a rhombus). It is, however, characterized by the rhombohedron crystallization.
 
Calcite is a citreous colouress or white and can become green, pink, peach, golden, orange, yellow, red, blue, grey, or black, etc., when other compounds blend with it during formation. 
 
Calcite, named for its chemistry, was first reported as "Kalkspate" by A.F. Cronstedt in 1758, as "Calc-Spar" by R. Jameson in 1804, and translated to "Calcite" by J.K. Freiesleben in 1836. The name was initially applied to crystals of Calcium Carbonate pseudomorphous after Celestine/Celestite and was subsequently applied to the more common mineral which had been known as Calcspar. 
 
The Chemical composition is: (Ca,Co)CO3
Hardness 2.5 - 3