mineral

Green Calcite (Onyx Marble)

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Pale green with brownish/white banding; Luster: Vitreous to waxy; Crystal structure: Trigonal; Cleavage: Perfect rhombohedral; Specific gravity: 2.71

Hardness: 3 on Mohs scale
Color: Pale green with brownish/white banding
Luster: Vitreous to waxy

Identified April 4, 2026More mineral →

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Physical properties

Hardness: 3 on Mohs scale; Color: Pale green with brownish/white banding; Luster: Vitreous to waxy; Crystal structure: Trigonal; Cleavage: Perfect rhombohedral; Specific gravity: 2.71

Formation & geological history

Formed through chemical precipitation in sedimentary environments, often near hot springs or in caverns as stalactites or stalagmites. This specimen appears to be of the variety often commercially (though inaccurately) called 'Green Onyx'.

Uses & applications

Used in the lapidary arts for carvings, bookends, and decorative stones. Also highly valued in the metaphysical community as a 'cleansing' stone.

Geological facts

Despite being called 'Green Onyx' in many shops, it is actually a variety of calcite or aragonite. True onyx is a form of chalcedony (quartz), which is much harder than this material.

Field identification & locations

Identify in the field by its softness—it can be easily scratched by a copper penny or a steel knife. It will also effervesce (fizz) if a drop of weak acid like vinegar is applied to it. Significant deposits are found in Mexico, Pakistan, and Brazil.

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