sedimentary

Chert (Jasper/Flint variety)

Microcrystalline quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Mustard yellow to brown (ochre); Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Mustard yellow to brown (ochre)
Luster: Dull to waxy

Identified June 13, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Mustard yellow to brown (ochre); Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of siliceous remains of organisms or chemical precipitation from silica-rich fluids in sedimentary basins. Primarily Paleozoic to Cenozoic eras.

Uses & applications

Historically used for stone tools (knapping). Currently used as landscaping stone, road aggregate, and sometimes as a minor gemstone (Jasper) in jewelry.

Geological facts

Chert is so hard it can scratch steel and was once the primary material for making arrowheads and spear points due to its sharp conchoidal fracture edges.

Field identification & locations

Identify by its 'shell-like' curved (conchoidal) fractures and its ability to scratch glass. Commonly found in riverbeds, glacial till, or as nodules within limestone/chalk layers.