mineral

Chalcedony

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Milky white, pale yellow, or light grey; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline (Trigonal/Monoclinic); Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.58-2.64.

Hardness: 6
Color: Milky white, pale yellow, or light grey
Luster: Waxy to vitreous

Identified June 15, 2026More mineral →

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Physical properties

Formation & geological history

Formed from the deposition of silica from aqueous solutions at relatively low temperatures, often in volcanic or sedimentary environments. Most examples are found in fissures, geodes, or as secondary fillings in rock cavities.

Uses & applications

Used primarily for semi-precious jewelry (beads, cabochons), ornamental carvings, and historically for making tools or seals due to its durability and clean fracture.

Geological facts

Chalcedony is actually composed of microcrystalline quartz and moganite. The name is believed to be derived from the ancient Greek port city of Chalkedon in Asia Minor.

Field identification & locations

Identify in the field by its waxy luster, translucency, and inability to be scratched by a steel pocketknife. Commonly found in desert regions, stream beds, or volcanic gravels worldwide.