mineral

Chalcedony (Agate/Quartz variety)

Cryptocrystalline Quartz (SiO2)

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

Hardness: 6
Color: Translucent greyish-white to pale yellow
Luster: Waxy to vitreous

Identified March 2, 2026More mineral →

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Physical properties

Formation & geological history

Formed via the deposition of silica from groundwater in cavities of igneous or sedimentary rocks, often in volcanic vugs or hydrothermal veins. Common throughout all geological eras.

Uses & applications

Used extensively in jewelry as cabochons, for ornamental carvings, and industrially in precision bearings or mortars and pestles due to its toughness and chemical resistance.

Geological facts

Chalcedony was highly prized in the ancient world for seals and amulets as it does not stick to hot wax. It is technically a mixture of the minerals quartz and moganite.

Field identification & locations

Identify by its waxy luster, conchoidal (shell-like) fracture, and inability to be scratched by a steel knife. Commonly found in riverbeds, volcanic fields, and desert regions globally.

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