mineral

Blue Calcite

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Pale blue to sky blue; Luster: Vitreous to waxy/pearly; Crystal structure: Trigonal/Rhombohedral; Cleavage: Perfect rhombohedral in three directions; Specific gravity: 2.71

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

Identified March 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed through sedimentary processes such as the accumulation of shell, coral, and algal debris in marine environments, or via precipitation from calcium-rich hot springs (tufa) or within caves. It can also form during low-grade metamorphism of limestone.

Uses & applications

Used primarily as decorative stone, in lapidary work for cabochons and carvings, as a source for lime in agriculture/cement industry, and widely collected by mineral enthusiasts for its metaphysical properties and aesthetic color.

Geological facts

Calcite is one of the most common minerals on Earth, but the blue variety is specialized. It often exhibits 'fluorescence' under UV light and is famous for its 'acid test' reaction, where it effervesces (fizzes) vigorously when exposed to dilute hydrochloric acid.

Field identification & locations

Identify in the field by its distinct rhombohedral cleavage, softness (can be scratched by a copper coin), and reaction to acid. It is commonly found in large deposits in Mexico, Brazil, and Africa. Collectors should look for a waxy texture and uniform pale blue hue.