mineral

Banded Calcite (often sold as Caribbean Calcite or Mexican Onyx)

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Blue, brown, white, and tan banding; Luster: Vitreous to waxy; Crystal structure: Trigonal; Cleavage: Perfect rhombohedral; Specific gravity: 2.71

Hardness: 3 on Mohs scale
Color: Blue, brown, white, and tan banding
Luster: Vitreous to waxy

Identified April 29, 2026More mineral →

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Physical properties

Hardness: 3 on Mohs scale; Color: Blue, brown, white, and tan banding; Luster: Vitreous to waxy; Crystal structure: Trigonal; Cleavage: Perfect rhombohedral; Specific gravity: 2.71

Formation & geological history

Formed through the precipitation of calcium carbonate in sedimentary environments, often in caves or hot springs where mineral-rich water deposits layers over time.

Uses & applications

Used primarily for decorative objects, carvings, lapidary arts, and as a popular metaphysical or collector's specimen.

Geological facts

While often marketed as 'Onyx' in the stone trade, it is actually a variety of calcite. True onyx is a form of chalcedony (quartz), which is much harder than calcite.

Field identification & locations

Identify in the field by its characteristic soft surface (can be scratched by a copper penny or steel knife) and its effervescence when exposed to weak acids like vinegar. Common in Pakistan, Mexico, and Brazil.

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Mineral/Rock

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mineral