mineral
Yellow Calcite / Banded Onyx Calcite
Calcite (CaCO3)
Mohs hardness: 3, Color: yellowish-orange with tan/white parallel bands, Luster: vitreous to silky, Crystal Structure: trigonal, Cleavage: perfect rhombohedral, Specific Gravity: 2.71
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Physical properties
Mohs hardness: 3, Color: yellowish-orange with tan/white parallel bands, Luster: vitreous to silky, Crystal Structure: trigonal, Cleavage: perfect rhombohedral, Specific Gravity: 2.71
Formation & geological history
Formed through chemical precipitation from calcium-rich water solutions in hydrothermal veins, caves, or sedimentary hot spring environments.
Uses & applications
Popular for lapidary work, polished decorative stones, carvings, tumbled pocket stones, and crystal healing/collecting.
Geological facts
Banded calcite is often commercially referred to as 'calcite onyx' or 'Mexican onyx', though true onyx is a microcrystalline quartz (chalcedony). Calcite reacts strongly by effervescing (fizzing) with dilute acid.
Field identification & locations
Identified by its soft hardness (easily scratched by a copper penny or steel nail), distinct parallel banding, and smooth polished surface texture. Commonly found in Mexico, Pakistan, Utah, and Brazil.
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