mineral

Calcite (Banded Calcite / Onyx Marble)

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Cream, white, and tan bands; Luster: Vitreous to resinous; Crystal structure: Trigonal; Cleavage: Perfect rhombohedral; Specific Gravity: 2.71

Hardness: 3 on Mohs scale
Color: Cream, white, and tan bands
Luster: Vitreous to resinous

Identified April 7, 2026More mineral →

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Physical properties

Hardness: 3 on Mohs scale; Color: Cream, white, and tan bands; Luster: Vitreous to resinous; Crystal structure: Trigonal; Cleavage: Perfect rhombohedral; Specific Gravity: 2.71

Formation & geological history

Formed through the precipitation of calcium-rich waters in caves (speleothems) or hot springs. This specimen displays the typical banding associated with travertine or 'Mexican Onyx.'

Uses & applications

Used for ornamental carvings, decorative stones, bookends, and as a calcium source in chemical industries. Also used in crystal healing practices.

Geological facts

Calcite is one of the most common minerals on Earth. It is famous for its double refraction (birefringence), where light passing through it splits into two rays.

Field identification & locations

Identify by its relative softness (can be scratched by a copper coin) and its lively reaction (fizzing) when a drop of weak acid, like vinegar, is applied. Found globally in limestone regions.

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