sedimentary

Banded Calcite (Onyx Marble)

Calcite (CaCO3) / Travertine

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: Honey-yellow, cream, and orange-brown banding; Luster: Vitreous to resinous (high polish); Crystal structure: Trigonal; Cleavage: Perfect rhombohedral in raw form; Specific Gravity: ~2.71

Hardness: 3 on Mohs scale
Color: Honey-yellow, cream, and orange-brown banding
Luster: Vitreous to resinous (high polish)

Identified October 3, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the rapid chemical precipitation of calcium carbonate from mineral-rich spring waters, thermal hot springs, or inside limestone caves (speleothems/travertine).

Uses & applications

Commonly carved and polished into ornamental decorative objects like eggs, spheres, bowls, figurines, bookends, and architectural tiles.

Geological facts

Widely traded commercially as 'Mexican Onyx' or 'Green/Honey Onyx', but it is not true onyx (which is a banded silicate chalcedony). It is composed almost entirely of the carbonate mineral calcite or aragonite.

Field identification & locations

Can be identified and differentiated from true quartz onyx by its low hardness (easily scratched by a copper coin or steel nail) and strong effervescence when exposed to dilute hydrochloric acid. Major producers include Pakistan, Mexico, Turkey, and Iran.