mineral

Chalcedony on Matrix

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Translucent grey to white; Luster: Waxy to vitreous; Crystal structure: Trigonal/Monoclinic (cryptocrystalline); Cleavage: None; Specific gravity: 2.58-2.64

Hardness: 6
Color: Translucent grey to white
Luster: Waxy to vitreous

Identified June 20, 2026More mineral →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Translucent grey to white; Luster: Waxy to vitreous; Crystal structure: Trigonal/Monoclinic (cryptocrystalline); Cleavage: None; Specific gravity: 2.58-2.64

Formation & geological history

Formed from the deposition of silica-rich fluids in cavities within volcanic rocks or sedimentary environments. It often exhibits a botryoidal (grape-like) habit and forms at relatively low temperatures.

Uses & applications

Used primarily in lapidary arts for jewelry, carvings, and as a collector's mineral specimen. Historically used for making tools and seals.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen even under a microscope. It is the group name for many common minerals including agate, jasper, and onyx.

Field identification & locations

Identify by its waxy luster, lack of cleavage, and ability to scratch glass. Commonly found in basalt cavities (vesicles) or as nodules in limestone. Collectors should look for smoothness and translucency.