mineral

Chalcedony

Silicon Dioxide (SiO2)

Hardness: 7 on the Mohs scale. Color: White, grey, yellow, brown, or light blue. Luster: Waxy to vitreous. Crystal structure: Trigonal (microcrystalline quartz). Cleavage: None. Specific gravity: 2.60-2.65.

Hardness: 7 on the Mohs scale
Color: White, grey, yellow, brown, or light blue
Luster: Waxy to vitreous

Identified July 28, 2026More mineral →

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Physical properties

Formation & geological history

Formed at low temperatures from silica-rich aqueous solutions, often depositing in cavities, fractures, and vesicles in volcanic or sedimentary rocks.

Uses & applications

Used for ornamental objects, carvings, lapidary work, jewelry, and spiritual collecting.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen easily without high magnification. It forms the parent material for many other gem varieties like agate, jasper, and onyx.

Field identification & locations

Can be identified in the field by its waxy luster, conchoidal fracture, and lack of visible crystal faces. Found worldwide, commonly in riverbeds and weathered volcanic regions.