mineral

Chalcedony (Quartz)

Silicon dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: translucent white to greyish-blue; Luster: waxy to dull; Crystal Structure: Cryptocrystalline (hexagonal system); Cleavage: none; Fracture: conchoidal.

Hardness: 6
Color: translucent white to greyish-blue
Luster: waxy to dull

Identified July 21, 2026More mineral →

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Physical properties

Hardness: 6.5-7 Mohs; Color: translucent white to greyish-blue; Luster: waxy to dull; Crystal Structure: Cryptocrystalline (hexagonal system); Cleavage: none; Fracture: conchoidal.

Formation & geological history

Formed from the deposition of silica-rich water in volcanic cavities or sedimentary layers at relatively low temperatures. It is found in geodes, veins, and as a primary constituent of chert.

Uses & applications

Used in jewelry (cabochons), as an abrasive, for precision mechanical components, and as a popular specimen for rock collectors.

Geological facts

Chalcedony was used as early as the Bronze Age in the Mediterranean (e.g., Minoan Crete) for seals and jewelry. It is a broad category that includes agate, jasper, and carnelian.

Field identification & locations

Look for a waxy luster and smooth, shell-like (conchoidal) breaks. It is very hard and will scratch glass. Common in riverbeds and desert regions with volcanic history.