mineral

Gray Chalcedony Gemstone

Chalcedony (SiO2)

Hardness: 6.5-7 Mohs, Color: Gray to bluish-gray, Luster: Waxy to vitreous, Crystal Structure: Trigonal (microcrystalline), Cleavage: None, Specific Gravity: 2.58-2.64

Hardness: 6

Identified July 1, 2026More mineral →

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Physical properties

Hardness: 6.5-7 Mohs, Color: Gray to bluish-gray, Luster: Waxy to vitreous, Crystal Structure: Trigonal (microcrystalline), Cleavage: None, Specific Gravity: 2.58-2.64

Formation & geological history

Formed by the deposition of silica from water in cavities or fissures in volcanic or sedimentary rocks at low temperatures. Common in various geological ages.

Uses & applications

Used primarily in jewelry as beads or cabochons, for ornamental carvings, and as a common specimen for crystal healing collectors.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen even under a microscope. It has been used for seals and cameos since ancient times.

Field identification & locations

Identified in the field by its waxy luster, conchoidal fracture, and hardness. Often found in riverbeds, desert pavements, and near volcanic outcrops globally.