mineral

Grey Chalcedony

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs), Color: Translucent grey to bluish-grey, Luster: Waxy to vitreous when polished, Crystal structure: Cryptocrystalline, Fracture: Conchoidal, Specific gravity: 2.6-2.64

Hardness: 6

Identified July 2, 2026More mineral →

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Physical properties

Hardness: 6.5-7 (Mohs), Color: Translucent grey to bluish-grey, Luster: Waxy to vitreous when polished, Crystal structure: Cryptocrystalline, Fracture: Conchoidal, Specific gravity: 2.6-2.64

Formation & geological history

Formed through the deposition of silica from aqueous solutions at relatively low temperatures, often in volcanic rock cavities or sedimentary environments as nodules.

Uses & applications

Used primarily in jewelry (cabochons and beads), ornamental carvings, and stone healing practices; historically used for seals and intaglios.

Geological facts

Chalcedony is one of the oldest gemstones known to man, with jewelry found in archaeological sites dating back to the Bronze Age. The name is believed to come from the ancient Greek town of Chalcedon.

Field identification & locations

Look for a microcrystalline structure with no visible crystals, a waxy feel on unpolished surfaces, and a translucent quality. Commonly found in riverbeds or volcanic deposits globally, including Brazil, India, and the USA.