mineral
Polished banded calcite (onyx marble)
Calcite, CaCO₃; commonly marketed as “honey onyx” or “Mexican onyx”
AI-generated identification · may be incorrectHardness 3 Mohs; cream, honey-yellow, white, and reddish-brown bands; vitreous to pearly luster; translucent; rhombohedral crystal structure with perfect rhombohedral cleavage. It reacts readily with dilute hydrochloric acid.
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Physical properties
Hardness 3 Mohs; cream, honey-yellow, white, and reddish-brown bands; vitreous to pearly luster; translucent; rhombohedral crystal structure with perfect rhombohedral cleavage. It reacts readily with dilute hydrochloric acid.
Formation & geological history
A human-cut and polished specimen of banded calcite, formed when mineral-rich groundwater precipitated successive layers in caves, springs, or cavities. It is generally Quaternary to younger, though the exact age depends on the deposit.
Uses & applications
Used for ornamental carvings, cabochons, small décor, and polished slabs; softer than quartz onyx and unsuitable for demanding countertops or heavy-wear jewelry.
Geological facts
“Onyx marble” is a commercial name, not true silicate onyx. The cloudy internal texture and easy acid reaction distinguish it from quartz-based banded agate.
Field identification & locations
Identify by its low hardness, waxy/translucent appearance, banding, and calcite cleavage; common sources include Mexico, Pakistan, Turkey, Iran, and Afghanistan. Avoid vinegar or acid testing on valuable polished pieces.
