mineral

Chalcedony (Tumbled)

Silicon Dioxide (SiO2)

Hardness: 6.5-7.0 (Mohs); Color: Waxy brown, grey, or tan; Luster: Vitreous to waxy; Crystal structure: Hexagonal (cryptocrystalline); Cleavage: None; Specific gravity: 2.58–2.64

Hardness: 6
Color: Waxy brown, grey, or tan
Luster: Vitreous to waxy

Identified March 25, 2026More mineral →

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Physical properties

Hardness: 6.5-7.0 (Mohs); Color: Waxy brown, grey, or tan; Luster: Vitreous to waxy; Crystal structure: Hexagonal (cryptocrystalline); Cleavage: None; Specific gravity: 2.58–2.64

Formation & geological history

Formed through the deposition of silica-rich groundwater in cavities of igneous rocks or sedimentary fossils. Can range from Recent to millions of years old.

Uses & applications

Used primarily in semi-precious jewelry, as pocket stones for crystal healing, and as abrasive polishing media. Historically used for making seals and figurines.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are so small they can only be seen under extreme magnification. It has been used by humans for bead-making since the Bronze Age.

Field identification & locations

Identify by its waxy luster, conchoidal fracture (if broken), and translucency. Common in river beds and volcanic regions like the American Southwest, Brazil, and India.