mineral
Grey Chalcedony (Tumbled Moon)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs scale); Color: translucent grey to bluish-grey; Luster: waxy to vitreous; Crystal structure: Trigonal (monocrystalline subunits); Cleavage: None; Specific Gravity: 2.6-2.64.
- Hardness
- 6
- Color
- translucent grey to bluish-grey
- Luster
- waxy to vitreous
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: translucent grey to bluish-grey; Luster: waxy to vitreous; Crystal structure: Trigonal (monocrystalline subunits); Cleavage: None; Specific Gravity: 2.6-2.64.
Formation & geological history
Formed from the deposition of silica from aqueous solutions in volcanic cavities and sedimentary environments at relatively low temperatures.
Uses & applications
Used primarily in jewelry, ornamental carvings, and 'metaphysical' retail. Also used industrially in precision bearings and mortars/pestles due to its toughness.
Geological facts
Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen under a normal microscope. When it occurs in bands, it is called agate; when solid grey/blue, it is simply chalcedony.
Field identification & locations
Identify by its waxy luster, translucency when held to light, and its inability to be scratched by a steel knife. Commonly found in Brazil, India, and the USA.
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