sedimentary

Chert (variations include Flint/Jasper)

Chert (Silicon Dioxide, SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Gray, tan, brown, or dull green with waxy luster; Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.

Hardness: 7 (Mohs scale)
Color: Gray, tan, brown, or dull green with waxy luster

Identified April 3, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the accumulation of siliceous remains of organisms (like diatoms or radiolaria) or through chemical precipitation in marine or groundwater environments. Found in sedimentary beds ranging from Precambrian to Cenozoic.

Uses & applications

Historically used for stone tools (arrowheads); currently used as a raw material for ceramics, construction aggregate, and occasionally as semi-precious gemstones (Jasper/Agate).

Geological facts

Chert was one of the most important minerals for early humans because its conchoidal fracture creates extremely sharp edges perfect for knives, scrapers, and projectiles.

Field identification & locations

Identify by its extreme hardness (scratches glass), waxy/dull luster, and distinctive curved (conchoidal) surface when broken. Found commonly in limestone outcrops or as river pebbles.