sedimentary

Banded Calcite (often sold as 'Green Onyx')

Calcite (Calcium Carbonate, CaCO3)

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 →

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.

Other sedimentary specimens

See all

Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary

Shale or Slaty Mudstone

Argillaceous sedimentary rock

sedimentary

Sandstone

Arenite (primarily SiO2)

sedimentary

Chert Breccia

Brecciated Chert (Microcrystalline Silica)

sedimentary

Sandstone

Arenite

sedimentary

Sandstone (Quartz-rich)

Arenite (SiO2)

sedimentary