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

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.

Identified on: 4/29/2026

Mode: Standard