Banded Calcite (often sold as 'Mexican Onyx' or 'Green Onyx')

Physical Properties

Hardness: 3 on Mohs scale. Color: Banded patterns of green, white, brown, and cream. Luster: Vitreous to silky. Crystal structure: Trigonal (often microcrystalline in this form). Cleavage: Perfect rhombohedral. Specific gravity: 2.71.

Formation & Geological History

Formed as a chemical sedimentary precipitate from cold-water springs or in caves as dripstone (travertine). Layers are deposited over time, often containing impurities like iron or copper that create the distinct color bands.

Uses & Applications

Used primarily for ornamental purposes including sculptures, spheres, bookends, vases, and interior design accents like tiles or sink basins.

Geological Facts

Despite being called 'Onyx' in the trade, it is not true Onyx (which is a form of chalcedony/quartz). This material is much softer and will react (fizz) with weak acids like vinegar.

Field Identification & Locations

Identify by its relative softness (can be scratched by a copper penny or steel knife) and its distinct parallel banding. It is commonly found in Mexico, Pakistan, and Turkey.

Identified on: 4/18/2026

Mode: Standard