mineral

Blue Calcite

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Pale sky blue to grayish blue; Luster: Vitreous to waxy; Crystal Structure: Trigonal/Rhombohedral; Cleavage: Perfect rhombohedral in three directions; Specific Gravity: 2.71.

Hardness: 3 on Mohs scale
Color: Pale sky blue to grayish blue
Luster: Vitreous to waxy

Identified March 14, 2026More mineral →

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Physical properties

Formation & geological history

Formed through sedimentary processes or as a secondary mineral in igneous hydrothermal environments. Found in large massive forms or as crystals within limestone or marble deposits worldwide; most blue specimens are found in sedimentary beds.

Uses & applications

Primary use in metaphysical collecting and home decor. Industrial varieties of calcite are used in cement, agriculture (soil treatment), and as a white pigment. Higher quality blue specimens are carved into cabochons or decorative spheres.

Geological facts

Blue Calcite is often very sensitive to acid and will effervesce (fizz) if a drop of vinegar or diluted HCl is applied. It is known in geological circles for its double refraction (birefringence), where light entering the crystal splits into two rays.

Field identification & locations

Identify in the field by its characteristic 'soapy' or waxy feel and rhombohedral cleavage planes. It can be scratched by a copper penny but not by a fingernail. Commonly found in Madagascar, Mexico, and Brazil.