mineral

Polished banded calcite sphere (often sold as onyx marble)

Calcite, CaCO₃; likely banded calcite marketed as “onyx”

AI-generated identification · may be incorrect

Cream to honey-yellow translucent bands with orange-brown veining and a polished luster; calcite has Mohs hardness 3, trigonal crystal structure, and perfect rhombohedral cleavage. The photo alone cannot confirm the mineral; similar spheres may be aragonite or other carbonate stone.

Identified October 3, 2026More mineral →

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Physical properties

Formation & geological history

Formed as carbonate precipitates in caves or mineral-rich springs, commonly accumulating in bands; such deposits can form over thousands to millions of years. This sphere was cut and polished from natural stone.

Uses & applications

Decorative collectible and ornamental carving; too soft for most everyday jewelry or construction use.

Geological facts

“Onyx marble” is a trade name for banded calcite and is not true silica-based onyx.

Field identification & locations

Look for translucent, curved or irregular bands and relatively low hardness; calcite fizzes with dilute acid, but testing can damage a polished specimen. Banded calcite occurs in Mexico, Pakistan, Turkey, and elsewhere.