mineral

Banded calcite (possibly onyx marble)

Calcite, CaCO₃; banded decorative calcite commonly sold as “onyx”

AI-generated identification · may be incorrect

Black-to-gray and cream bands, vitreous to waxy luster, and likely rhombohedral cleavage; calcite has Mohs hardness 3 and specific gravity about 2.7. The specimen appears to be a rough, broken piece; visual identification alone cannot confirm its composition.

Identified October 13, 2026More mineral →

Explore Banded calcite (possibly onyx marble) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Banded calcite forms when calcium-carbonate-rich water deposits successive layers in caves, veins, or springs. Its age depends on the deposit and cannot be determined from the image.

Uses & applications

Used for ornamental carvings, small décor, and occasionally polished panels; it is too soft for most durable jewelry or heavy-use surfaces.

Geological facts

Commercial “onyx marble” is often banded calcite, not true onyx, which is a variety of quartz chalcedony.

Field identification & locations

Look for strong cream-and-dark banding and test cautiously: calcite is readily scratched by a copper coin and fizzes with dilute acid. Banded calcite is found in deposits worldwide, including Mexico, Pakistan, and the United States.