sedimentary

Chert or flint fragment

Microcrystalline quartz (SiO₂), likely silicified rock

AI-generated identification · may be incorrect

Hardness about 7 Mohs; brown-red translucent conchoidal-fracture core with a pale cream, chalky-looking outer cortex. Waxy to dull luster and no visible cleavage; the pale coating may be weathered cortex or adhering limestone.

Identified August 10, 2026More sedimentary →

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Physical properties

Formation & geological history

Typically forms when silica replaces or fills pores in limestone, chalk, or marine sediments during diagenesis, commonly from Paleozoic to Cenozoic deposits. Exact age and locality cannot be determined from the image.

Uses & applications

Used historically for sharp tools and fire-starting; today it is mainly a teaching, archaeological, or lapidary/collecting material, with limited commercial value.

Geological facts

Conchoidal fracture and very high hardness distinguish chert from ordinary limestone; a fresh edge can produce a sharp cutting surface and may scratch glass.

Field identification & locations

Common in sedimentary terrains worldwide, especially chalk and limestone regions. Confirm with a glass-scratch test and streak test; avoid destructive testing if it may be archaeological.