mineral

Banded Calcite (known as Mexican Onyx or Calcite Alabaster)

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Cream, tan, brown, and white banded patterns; Luster: Vitreous to pearly; Crystal structure: Trigonal/Hexagonal; Cleavage: Perfect rhombohedral.

Hardness: 3 on Mohs scale
Color: Cream, tan, brown, and white banded patterns
Luster: Vitreous to pearly

Identified May 7, 2026More mineral →

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Physical properties

Hardness: 3 on Mohs scale; Color: Cream, tan, brown, and white banded patterns; Luster: Vitreous to pearly; Crystal structure: Trigonal/Hexagonal; Cleavage: Perfect rhombohedral.

Formation & geological history

Formed by the precipitation of calcium carbonate from cold water solutions in caves or spring deposits (travertine). Layers represent different pulses of mineral-rich water over centuries.

Uses & applications

Commonly used for ornamental carvings, bookends, decorative bowls, and jewelry. Also used as a metaphysical stone for grounding.

Geological facts

Despite being called 'Onyx' in the trade, it is actually a variety of calcite, which is much softer than true chalcedony onyx. It will react and fizz if exposed to weak acid.

Field identification & locations

Identified by its distinctive parallel banding and softness (can be scratched by a copper penny or knife). Commonly found in Mexico, Pakistan, and the United States (Utah/Arizona).

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