mineral

Banded Calcite (Mexican Onyx)

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Cream, white, and pale green bands; Luster: Vitreous to waxy; Crystal Structure: Trigonal (often found in massive form); Cleavage: Perfect rhombohedral.

Hardness: 3 on Mohs scale
Color: Cream, white, and pale green bands
Luster: Vitreous to waxy

Identified May 9, 2026More mineral →

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Physical properties

Hardness: 3 on Mohs scale; Color: Cream, white, and pale green bands; Luster: Vitreous to waxy; Crystal Structure: Trigonal (often found in massive form); Cleavage: Perfect rhombohedral.

Formation & geological history

Formed by the precipitation of calcium carbonate from cold water springs or drip water in limestone caves. It is a sedimentary chemical precipitate, usually from the Cenozoic era.

Uses & applications

Commonly used for decorative carvings, laboratory surfaces, ornamental towers, spheres, and metaphysical collecting. Too soft for high-impact construction or most jewelry.

Geological facts

Often mislabeled as 'Onyx' in the trade, true Onyx is a form of chalcedony (silica), whereas this specimen is Calcite. It is highly reactive to dilute hydrochloric acid.

Field identification & locations

Identify by its characteristic parallel banding, extreme softness (it can be scratched by a copper penny or steel knife), and translucent nature. Frequently sourced from Mexico, Pakistan, and Utah.

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