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

Identified April 4, 2026More mineral →

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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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