mineral

Chalcedony

Cryptocrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Translucent grey to milky white; Luster: Waxy to vitreous; Crystal structure: Trigonal/Monoclinic (microscopic fibers); Cleavage: None; Fracture: Conchoidal; Specific gravity: 2.6-2.64

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

Identified May 29, 2026More mineral →

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Physical properties

Formation & geological history

Forms through the precipitation of silica-rich fluids in volcanic cavities, sedimentary rocks, and hydrothermal veins. It often forms in low-temperature environments over millions of years.

Uses & applications

Used extensively in jewelry for cabochons and beads, as well as in industrial applications for precision bearings and abrasive tools due to its hardness.

Geological facts

The name comes from the Latin word 'chalcedonius', derived from the name of the ancient Greek town of Chalcedon in Asia Minor. It was historically one of the most common materials for making cylinder seals in Mesopotamia.

Field identification & locations

Identified in the field by its waxy luster, lack of cleavage, and smooth, curved (conchoidal) fracture surfaces. It can often be found along riverbeds or as nodules in volcanic host rocks.