sedimentary

Chert (Flint)

Chert (SiO2)

Hardness: 7; Color: Dark brown to black; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7
Color: Dark brown to black
Luster: Waxy to dull

Identified May 24, 2026More sedimentary →

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Physical properties

Hardness: 7; Color: Dark brown to black; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed through the accumulation of siliceous remains of marine organisms or via chemical precipitation in sedimentary basins. Specimens can range from Precambrian to nearly modern ages.

Uses & applications

Historically used for stone tools and weapons (lithics) and for sparking fires. Currently used as road aggregate and as semi-precious stones for lapidary work.

Geological facts

This specimen appears to be a 'flake' or 'blade,' possibly a byproduct of tool-making called debitage. Flint was one of the most important minerals for early human technological development.

Field identification & locations

Identified by its waxy luster, extreme hardness (scratches glass), and shell-like (conchoidal) fracture patterns. Frequently found in limestone and chalk deposits globally.