sedimentary

Banded Calcite / Onyx Marble

Calcite (Travertine / Onyx Marble, CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: mottled cream, tan, beige, pinkish-brown, and translucent banded patches; Luster: vitreous to resinous, polished; Cleavage: rhombohedral in raw form; Specific Gravity: 2.71

Hardness: 3 on Mohs scale
Luster: vitreous to resinous, polished

Identified October 3, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed as chemical sedimentary rock precipitated from carbonate-rich mineral spring waters, thermal hot springs, or inside limestone caves as travertine or flowstone.

Uses & applications

Commonly carved and polished into decorative shapes such as eggs, spheres, bookends, vases, tiles, and ornamental carvings.

Geological facts

Often commercially mislabeled in trade as 'Mexican Onyx' or 'Green Onyx', it is actually a form of calcite (travertine) rather than true cryptocrystalline quartz onyx, making it considerably softer and effervescent with dilute acid.

Field identification & locations

Identifiable by its soft hardness (scratched easily by a copper penny or steel nail), translucency in pale bands, and vigorous reaction (effervescence) to weak hydrochloric acid. Commonly sourced from Pakistan, Mexico, Turkey, and Iran.