mineral

Chalcedony (Agate/Carnelian type)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: semi-translucent white to yellowish-orange; Luster: waxy to vitreous; Crystal Structure: Cryptocrystalline (Trigonal/Monoclinic); Cleavage: none; Specific Gravity: 2.58-2.64

Hardness: 6
Color: semi-translucent white to yellowish-orange
Luster: waxy to vitreous

Identified May 9, 2026More mineral →

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Physical properties

Formation & geological history

Formed from the deposition of silica from groundwater in cavities of volcanic or sedimentary rocks. It often forms at relatively low temperatures.

Uses & applications

Used primarily in jewelry as gemstones (cabochons), ornamental carvings, and historical use for seals, cameos, and abrasive tools.

Geological facts

Chalcedony was highly prized in the ancient world; the name comes from the ancient Greek town of Chalcedon in Asia Minor. It is the broad term for microcrystalline quartz.

Field identification & locations

Identify by its waxy luster, lack of visible crystals, and ability to scratch glass. Commonly found in riverbeds, desert pavements, and volcanic regions (e.g., Brazil, USA - especially Oregon and Arizona).

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