mineral
Grey Agate
Silicon Dioxide (SiO2) - variety: Agate/Chalcedony
Hardness: 6.5-7 on Mohs scale. Color: Grey, black, white, sometimes banded. Luster: Waxy to vitreous. Crystal system: Trigonal (cryptocrystalline). Cleavage: None. Specific Gravity: 2.60-2.65.
- Hardness
- 6
- Color
- Grey, black, white, sometimes banded
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Grey, black, white, sometimes banded. Luster: Waxy to vitreous. Crystal system: Trigonal (cryptocrystalline). Cleavage: None. Specific Gravity: 2.60-2.65.
Formation & geological history
Formed in volcanic and metamorphic environments as silica-rich water fills cavities (geodes) or cracks in rocks. Layering occurs over thousands of years as thin layers of minerals crystallize.
Uses & applications
Used primarily in jewelry making (beads, cabochons), ornamental decoration, and as industrial mortar and pestles due to its hardness and resistance to chemicals.
Geological facts
Grey agate is often called 'The Stabilizer.' While common, high-quality specimens showing distinct concentric banding or druzy (crystal) pockets are highly sought after by collectors.
Field identification & locations
Identify in the field by its conchoidal fracture (smooth, curved breaks) and its inability to be scratched by a steel knife. It is frequently found in riverbeds or near volcanic basalt outcrops.
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