mineral

Chalcedony

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Milky white, translucent grey; Luster: Waxy to vitreous; Crystal Structure: Trigonal (cryptocrystalline); Cleavage: None; Fracture: Conchoidal.

Hardness: 6
Color: Milky white, translucent grey
Luster: Waxy to vitreous

Identified June 28, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Milky white, translucent grey; Luster: Waxy to vitreous; Crystal Structure: Trigonal (cryptocrystalline); Cleavage: None; Fracture: Conchoidal.

Formation & geological history

Forms at low temperatures in the cavities of volcanic rocks or sedimentary environments. It is a microcrystalline variety of quartz deposited from silica-rich aqueous solutions.

Uses & applications

Used primarily in jewelry as gemstones, beads, and cabochons. Historically used for making tools due to its conchoidal fracture, and currently used in industrial abrasives.

Geological facts

Chalcedony was used in the ancient world for cylinder seals and carved cameos. In ancient Greece, it was named after the town of Chalcedon in Asia Minor.

Field identification & locations

Identifiable by its translucent appearance, waxy luster, and lack of visible crystals. Commonly found in riverbeds, desert regions, and volcanic deposits world-wide.