Cobaltian Calcite (Cobaltoan Calcite)

Hardness: 3 (Mohs Scale). Color: Ranges from pale pink to deep rose-red, often vibrant due to cobalt. Luster: Vitreous to dull. Crystal Structure: Trigonal. Cleavage: Perfect rhombohedral cleavage, meaning it breaks into distinctive rhombic shapes. Specific Gravity: 2.71. Streak: White.

Cobaltian Calcite is a variety of calcite where a small percentage of cobalt (Co2+) ions substitute for calcium (Ca2+) ions in the mineral's crystal lattice. This substitution is responsible for its characteristic pink to red coloration. It typically forms in hydrothermal veins associated with cobalt-bearing mineral deposits. Its formation is secondary and occurs at relatively low temperatures.

Primarily used as a collector's mineral due to its striking color and aesthetic appeal. It is sometimes cut into cabochons or used in small ornamental carvings, though its relative softness limits extensive use in jewelry.

Also known as 'Cobaltoan Calcite,' it's highly sought after by mineral collectors for its vivid pink and red hues. The intensity of the color depends on the amount of cobalt present in the crystal structure. It is sometimes mistaken for rhodochrosite due to similar coloring, but calcite's rhombohedral cleavage and reaction to acid help distinguish it.

Can be identified in the field by its distinct pink to red color, its relatively low hardness (easily scratched with a knife), and its perfect rhombohedral cleavage. It will also effervesce (fizz) vigorously when a drop of dilute hydrochloric acid is applied to it, a characteristic property of all calcites. It is commonly found in areas rich in cobalt mineralization, such as the Democratic Republic of Congo (historically a major source) and parts of Morocco, Spain, and Mexico. Collectors should look for well-formed crystals in vugs and veins within host rocks.