sedimentary

Banded Calcite (often sold as Yellow Aragonite or Onyx)

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale (soft); Color: Cream, honey yellow, and white bands; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal; Cleavage: Perfect rhombohedral.

Hardness: 3 on Mohs scale (soft)
Color: Cream, honey yellow, and white bands
Luster: Vitreous to waxy

Identified April 13, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale (soft); Color: Cream, honey yellow, and white bands; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal; Cleavage: Perfect rhombohedral.

Formation & geological history

Formed in caves or hot springs through the precipitation of calcium carbonate from mineral-rich waters. This specific specimen appears to be a water-worn or tumbled river pebble or decorative stone.

Uses & applications

Used primarily for decorative purposes, ornamental carvings, tumbled pocket stones, and in the metaphysical/crystal healing community.

Geological facts

While often commercially mislabeled as 'Onyx' (which is technically a form of chalcedony/silica), 'Mexican Onyx' or 'Cave Onyx' is actually banded calcite. It is much softer than true onyx and can be scratched with a copper penny.

Field identification & locations

Identify in the field by its softness and its reaction to cold dilute hydrochloric acid (it will fizz). Look for rhythmic, parallel color banding. Commonly found in limestone-rich regions and cave systems.