Rock Identifier
Banded Calcite (Calcium Carbonate (CaCO3)) — mineral
mineral

Banded Calcite

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Yellow, honey-brown, and white banding; Luster: Vitreous to waxy; Crystal Structure: Trigonal/Hexagonal; Cleavage: Perfect rhombohedral.

Hardness
3 on Mohs scale
Color
Yellow, honey-brown, and white banding
Luster
Vitreous to waxy
Identified More mineral
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Physical properties

Hardness: 3 on Mohs scale; Color: Yellow, honey-brown, and white banding; Luster: Vitreous to waxy; Crystal Structure: Trigonal/Hexagonal; Cleavage: Perfect rhombohedral.

Formation & geological history

Formed through the chemical precipitation of calcium carbonate from mineral-rich waters, often in cave environments as flowstone (onyx-marble) or in hot spring deposits like travertine.

Uses & applications

Used for decorative carvings, lapidary cabochons, metaphysical collecting, and historically as an architectural ornamental stone (Mexican Onyx).

Geological facts

While often sold as 'Honey Onyx' or 'Banded Onyx' in the gemstone trade, it is scientifically calcite and much softer than true chalcedony-based onyx. It reacts and fizzes when exposed to weak acids like vinegar.

Field identification & locations

Identify by its rhombohedral cleavage, relative softness (can be scratched by a copper penny or knife), and distinct parallel color banding. Widely found in Mexico, USA (Utah), and Brazil.