mineral

Tumbled banded calcite (onyx marble)

Banded calcite, CaCO₃; commonly marketed as “honey onyx” or “Mexican onyx”

AI-generated identification · may be incorrect

Typically cream, white, golden, and brown with translucent rhythmic banding; vitreous to waxy luster, trigonal crystal structure, perfect rhombohedral cleavage, Mohs hardness 3, and specific gravity about 2.7. The spherical form is polished and tumbled.

Identified August 25, 2026More mineral →

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Physical properties

Formation & geological history

Forms when carbonate-rich groundwater deposits successive layers of calcite in caves, fractures, or hot-spring settings; coloration commonly comes from iron oxides and other impurities. Deposits are generally geologically young compared with crystalline basement rocks.

Uses & applications

Used for ornamental carvings, beads, cabochons, décor, and polished spheres; softer than quartz and unsuitable for demanding flooring or heavily worn jewelry.

Geological facts

Despite the trade name “onyx,” this material is calcite, not quartz chalcedony. It can fizz with dilute hydrochloric acid or vinegar, especially on a fresh surface.

Field identification & locations

Identify by softness, curved or wavy banding, translucency, and acid reaction; common sources include Mexico, Pakistan, Turkey, Argentina, and Afghanistan. Avoid harsh acids and ultrasonic cleaning.