sedimentary

Banded Calcite (Onyx Marble / Green Onyx)

Travertine / Banded Calcite (CaCO3) or Aragonite

AI-generated identification · may be incorrect

Hardness 3 on the Mohs scale, vitreous to silky or resinous luster when polished, trigonal crystal system (or orthorhombic if aragonite), specific gravity 2.71, pale green, cream, and orange-brown banded coloration, reacts strongly and effervesces with dilute hydrochloric acid.

Identified October 3, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed as chemical precipitate deposits from calcium-rich mineral springs or karst cave dripwaters (travertine or stalagmitic flowstone), often of Quaternary or Tertiary geological age.

Uses & applications

Commonly carved and polished into decorative objects like eggs, bowls, figurines, vases, tiles, and luxury ornamental stonework.

Geological facts

Commercial gemstone vendors commonly mislabel this material as 'Green Onyx' or 'Mexican Onyx', although true onyx is a cryptocrystalline variety of silica (chalcedony/quartz with Mohs hardness 7), whereas this material is much softer calcium carbonate.

Field identification & locations

Identified by its soft hardness (scratched easily by a copper penny or steel blade), low density compared to jade or quartz, effervescence with mild acid, and distinctive fibrous, translucent banding. Widely sourced from Pakistan, Mexico, Iran, and Turkey.