sedimentary

Chert (Quartz Variety)

Microcrystalline Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Cream, tan, or light brown; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Cream, tan, or light brown
Luster: Waxy to dull

Identified May 31, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Cream, tan, or light brown; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed from the accumulation of siliceous remains of microscopic organisms (like diatoms or radiolarians) or through the chemical precipitation of silica in sedimentary basins. Primarily found in marine limestone or dolostone.

Uses & applications

Historically used for stone tools (knapping); modernly used for road aggregate and as an abrasive in some industrial processes.

Geological facts

Chert is so hard it can scratch glass and steel. It was one of the most important minerals for early humans because of its ability to fracture into extremely sharp edges for blades and arrowheads.

Field identification & locations

Identify by its characteristic conchoidal (shell-like) fracture, extreme hardness, and smooth, waxy surface. Often found in nodes or beds within limestone formations.