mineral

Blue Calcite

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Pale sky blue to deep blue; Luster: Vitreous to waxy/pearly; Crystal structure: Trigonal/Rhombohedral; Cleavage: Perfect rhombohedral in three directions.

Hardness: 3 on Mohs scale
Color: Pale sky blue to deep blue
Luster: Vitreous to waxy/pearly

Identified July 14, 2026More mineral →

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Physical properties

Hardness: 3 on Mohs scale; Color: Pale sky blue to deep blue; Luster: Vitreous to waxy/pearly; Crystal structure: Trigonal/Rhombohedral; Cleavage: Perfect rhombohedral in three directions.

Formation & geological history

Formed in sedimentary environments through chemical precipitation or in metamorphic environments as coarse-grained marble. Blue coloration is often due to the presence of strontium or other impurities that affect the light absorption.

Uses & applications

Primarily used as a decorative stone, in lapidary work for cabochons and carvings, and as a popular specimen for metaphysical collectors.

Geological facts

Blue calcite is one of the softest minerals used in jewelry, meaning it is easily scratched. It is often found in large massive forms rather than distinct crystals. Massive blue calcite from Madagascar is world-renowned for its intense color.

Field identification & locations

Identify by its characteristic rhombohedral cleavage, softness (can be scratched by a copper penny), and its reaction to cold dilute hydrochloric acid (effervescence). Commonly found in Madagascar, Mexico, and Brazil.