sedimentary

Brown chert (flint)

Microcrystalline quartz (SiO₂), varieties called chert or flint

AI-generated identification · may be incorrect

Brown, opaque to slightly translucent edges, with a dull-to-waxy luster and conchoidal fracture; Mohs hardness about 7. The image does not reveal its internal crystal structure or specific gravity.

Identified October 4, 2026More sedimentary →

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Physical properties

Brown, opaque to slightly translucent edges, with a dull-to-waxy luster and conchoidal fracture; Mohs hardness about 7. The image does not reveal its internal crystal structure or specific gravity.

Formation & geological history

Silica-rich sediment or replacement silica formed the rock; chert occurs in sedimentary layers and nodules across many geological ages. The specimen’s exact age and locality cannot be determined from the image.

Uses & applications

Chert has been used for stone tools and fire-starting; attractive pieces may be collected or made into small ornaments.

Geological facts

Its sharp, curved fracture surfaces were valuable for making prehistoric blades and arrowheads.

Field identification & locations

The brown, waxy-looking surface and sharp, curved fracture are consistent with chert, but visual identification alone is not definitive. Common worldwide in sedimentary rocks; similar pieces typically sell for about $1–$20, depending on size and appearance.