mineral

Chalcedony (Agate/Carnelian)

Cryptocrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: translucent white to pale orange/yellow; Luster: waxy to vitreous; Crystal structure: trigonal (microscopic); Cleavage: none; Specific gravity: 2.58–2.64

Hardness: 6
Color: translucent white to pale orange/yellow
Luster: waxy to vitreous

Identified May 23, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: translucent white to pale orange/yellow; Luster: waxy to vitreous; Crystal structure: trigonal (microscopic); Cleavage: none; Specific gravity: 2.58–2.64

Formation & geological history

Formed by the deposition of silica from groundwater in cavities of volcanic rocks (basalts) or sedimentary formations. Can occur at various geological ages from Precambrian to recent.

Uses & applications

Commonly used in jewelry as cabochons, for ornamental carvings, and industrially for precision bearings and mortars/pestles due to its toughness.

Geological facts

Chalcedony was highly prized in the ancient world for seals and amulets because wax does not stick to it. It is actually composed of tiny, microscopic intergrowths of quartz and moganite.

Field identification & locations

Identify by its waxy luster, lack of visible crystals, and translucent edges. Often found in riverbeds, beaches, or as nodules in volcanic field sites.

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