metamorphic
Green Onyx (Commercial Marble/Travertine)
CaCO3 (Calcite / Banded Limestone)
Hardness: 3 on Mohs scale; Color: Pale to deep green with reddish-brown and white banding; Luster: Vitreous to waxy when polished; Crystal structure: Trigonal; Specific gravity: 2.71
- Hardness
- 3 on Mohs scale
- Color
- Pale to deep green with reddish-brown and white banding
- Luster
- Vitreous to waxy when polished
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Physical properties
Hardness: 3 on Mohs scale; Color: Pale to deep green with reddish-brown and white banding; Luster: Vitreous to waxy when polished; Crystal structure: Trigonal; Specific gravity: 2.71
Formation & geological history
Formed by the precipitation of calcium carbonate from carbonate-rich waters, typically in hot springs or limestone caves over millions of years.
Uses & applications
Commonly used for ornamental objects, carvings, decorative bowls, tiles, and interior architectural elements.
Geological facts
In the commercial gemstone and stone-carving industry, this material is widely referred to as 'green onyx' or 'Mexican onyx,' though geologists properly classify it as a banded calcite or travertine (a type of limestone).
Field identification & locations
Easily scratched with a knife due to its low hardness (Mohs 3) and will effervesce (fizz) when exposed to dilute hydrochloric acid due to its carbonate composition.
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