sedimentary

Flint or chert fragment

Microcrystalline quartz (SiO₂), commonly called chert or flint

AI-generated identification · may be incorrect

Hardness about 7 Mohs; brown to tan, opaque, with a dull-to-waxy luster and conchoidal fracture producing sharp edges. It has no visible cleavage and consists of cryptocrystalline quartz, possibly with iron-oxide staining or fossil material.

Identified August 16, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater replaces or cements sediment, commonly within limestone or chalk; most examples range from Paleozoic to Cenozoic in age. This small piece appears naturally fractured or worked, but the image cannot confirm its origin.

Uses & applications

Historically used for stone tools, arrowheads, and fire-starting; today it is mainly a collector or educational specimen, with limited aggregate and decorative uses.

Geological facts

Fresh fractures are typically glassy and sharply conchoidal, a key distinction from many ordinary sandstones. Flint is commonly darker and associated with chalk, whereas “chert” is the broader geological term.

Field identification & locations

Common worldwide, especially in limestone and chalk regions. Field identification relies on hardness, inability to scratch it with steel, waxy texture, and conchoidal fracture; a streak or chemical test can help distinguish it from glass.