sedimentary
Banded Calcite (Green Onyx)
Calcite (CaCO3)
Hardness: 3 on Mohs scale; Color: Pale green to yellowish-green with brown/tan banding; Luster: Vitreous to waxy; Structure: Hexagonal; Clavage: Perfect rhombohedral.
- Hardness
- 3 on Mohs scale
- Color
- Pale green to yellowish-green with brown/tan banding
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 3 on Mohs scale; Color: Pale green to yellowish-green with brown/tan banding; Luster: Vitreous to waxy; Structure: Hexagonal; Clavage: Perfect rhombohedral.
Formation & geological history
Formed in caves or around cold springs as a chemical sedimentary deposit. It precipitates from calcium-rich water, leaving behind layered bands of calcite crystals.
Uses & applications
Used primarily for decorative carvings, small figurines, jewelry beads, and architectural accents like lamps or bowls.
Geological facts
Commonly mislabeled as 'Green Onyx' in the trade; however, true onyx is a form of chalcedony (silica), while this specimen is a soft calcium carbonate.
Field identification & locations
Identify by its softness (it can be scratched by a copper penny or steel knife) and its reaction to weak acid. Often found in Mexico, Pakistan, and Afghanistan.
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