sedimentary

Chalcedony (Chert/Flint)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: White, grey, waxy translucency; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.64.

Hardness: 6
Color: White, grey, waxy translucency
Luster: Waxy to dull

Identified June 3, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the chemical precipitation of silica-rich groundwater. It often occurs as nodules in limestone or as petrified wood and volcanic cavity fillings. It can range from precambrian to recent geological ages.

Uses & applications

Historically used for stone tools and weapons due to sharp edges when fractured. Currently used in jewelry as cabochons, for industrial abrasives, and as decorative landscaping stone.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen under a normal microscope. It has been used by humans for hundreds of thousands of years to create blades and arrowheads.

Field identification & locations

Identify in the field by its waxy luster, smoothness, and distinctive shell-like (conchoidal) fractures. Found globally in sedimentary basins and volcanic regions. Collectors look for translucency and color depth.