Cobalt-bearing Calcite-Spherocobaltite

A series between 'Cobalt-bearing Calcite' and Spherocobaltite

Cobaltoan dolomite and cobaltoan calcite are frequently mislabeled as spherocobaltite. Both cobaltoan calcite and cobaltoan dolomite may vary from light pink through some shade of red, sometimes grading into purple. Many validated visibly crystallized spherocobaltite specimens show peculiar curved dislocations, but that distinction is of unknown significance. Many cobaltoan carbonates are crystallized as simple rhombohedrons rather than as scalenohedrons or other dominant forms. That variance in crystal shapes has been confusing, although these forms are common among the carbonates. Cobaltoan calcite and cobaltoan dolomite are far more common than spherocobaltite and cobalt-dominant members of the dolomite group are unknown. Chave (1951) was one of the earliest studies to show that chemical substitution in calcite to dolomite is discontinuous. Between 15-20% mole percent of Mg in calcite yields ordering toward the dolomite structure. It is recommended that unless useful analytical data, etc. have been presented along with the photograph, an intermediate name should be used for members of this series.