sedimentary

Green Onyx (Banded Calcite / Travertine)

Calcite (CaCO3) / Travertine / Aragonite

AI-generated identification · may be incorrect

Mohs hardness 3; vitreous to resinous luster; translucent to opaque; olive to pale green with characteristic white, reddish-brown, or cream banding; trigonal crystal system; specific gravity around 2.71.

Identified October 3, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed as a chemical sedimentary rock by precipitation of calcium carbonate from mineral-rich groundwater or thermal hot springs, often forming banded cave deposits (flowstone) or travertine terraces.

Uses & applications

Commonly carved and polished into ornamental objects such as decorative eggs, spheres, bowls, vases, and tiles. Widely used in decorative crafts and lapidary art.

Geological facts

Despite commercially being called 'Green Onyx', it is actually a banded calcite or travertine rather than true onyx, which is a cryptocrystalline banded silicate variety of chalcedony quartz.

Field identification & locations

Distinguishable from true green chalcedony or jade by its softness (readily scratched by a copper penny or steel blade) and vigorous reaction/effervescence with dilute hydrochloric acid. Prominent sources include Pakistan, Mexico, Turkey, and Iran.