Sphaerocobaltite describes a pure cobalt carbonate, without calcium. Pure Sphaerocobaltite is quite uncommon, as the cobalt is usually mixed with calcium. This leads to confusion with the term Cobaltocalcite. Cobaltocalcite refers to an intermediary mineral between Calcite and Sphaerocobaltite in a solid solution series. It may be described as either a cobalt rich variety of Calcite, or a calcium rich variety of Sphaerocobaltite.
Sphaerocobaltite belongs to the calcite group of minerals, a group of related carbonates that are isomorphous with one another. They are similar in many physical properties, and may partially or fully replace one another, forming a solid solution series. All members of the calcite group crystallize in the trigonal system, and have perfect rhombohedral cleavage.