sedimentary

Banded Calcite (often sold as 'Green Onyx')

Calcite (Calcium Carbonate, CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale (can be scratched by a copper coin); Color: Pale green to white with brown/red banding; Luster: Vitreous to waxy; Crystal structure: Trigonal; Cleavage: Perfect rhombohedral; Specific gravity: 2.71

Hardness: 3 on Mohs scale (can be scratched by a copper coin)
Color: Pale green to white with brown/red banding
Luster: Vitreous to waxy

Identified May 26, 2026More sedimentary →

Explore Banded Calcite (often sold as 'Green Onyx') in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed through the precipitation of calcium carbonate from cold water springs or in caves as flowstone/travertine. It is relatively young in geological terms, often forming in the Quaternary period.

Uses & applications

Primarily used for decorative carvings, figurines, bookends, and low-cost jewelry. It is a popular material for ornamental stone craft due to its softness and translucency.

Geological facts

Despite being called 'Green Onyx' in the trade, it is not true onyx (which is a form of cryptocrystalline quartz). True onyx is much harder (Mohs 7), whereas this calcite is soft and will react/fizz if it comes into contact with even weak acids like vinegar.

Field identification & locations

Identify in the field by its softness (easily scratched by a steel blade) and its characteristic light-to-dark parallel banding. It is commonly found in Mexico, Pakistan, and Iran.