mineral

Chalcedony

Silicon Dioxide (SiO2)

Hardness: 6.5 to 7 on the Mohs scale. Color: Varies widely, often white, grey, bluish, or brownish with rusty iron-oxide matrix present on the surface. Luster: Waxy to vitreous. Crystal structure: Trigonal (microcrystalline quartz). Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.58 to 2.64.

Hardness: 6
Luster: Waxy to vitreous

Identified August 1, 2026More mineral →

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Physical properties

Formation & geological history

Forms in low-temperature environments through the deposition of silica-rich solutions in cavities, fractures, and pore spaces of rocks, commonly volcanic or sedimentary environments.

Uses & applications

Used in lapidary arts for making ornamental objects, carvings, beads, and jewelry, as well as valued by mineral collectors.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen easily with normal magnification. Varieties include agate, jasper, and onyx.

Field identification & locations

Identified by its waxy luster, conchoidal fracture, and lack of visible crystal faces in raw specimens. Commonly found worldwide in volcanic rock cavities and river gravels.