sedimentary

Chert (Flint)

Chert (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Yellowish-brown, tan, and dark gray; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 7 on Mohs scale
Color: Yellowish-brown, tan, and dark gray
Luster: Waxy to dull

Identified May 24, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments. Often found as nodules in limestone or chalk beds.

Uses & applications

Historically used for stone tools and weapons (arrowheads). Today used in road construction, as jewelry (when patterned), and occasionally for fire-starting in flintlock mechanisms.

Geological facts

Chert is so hard it can scratch glass. It has been used by humans for over 2 million years to create sharp edges. It is chemically identical to quartz but has a different internal structure.

Field identification & locations

Identify by its waxy appearance and shell-like (conchoidal) fractures where it has been chipped. Commonly found in gravel pits, riverbeds, and sedimentary rock outcrops.