sedimentary

Flint (Chert)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Black, dark grey, or brown; Luster: Waxy or dull; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Black, dark grey, or brown
Luster: Waxy or dull

Identified May 16, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Black, dark grey, or brown; Luster: Waxy or dull; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed as nodules in sedimentary rocks like chalk or limestone via the concentration of silica from organic sources (sponges, diatoms) during diagenesis.

Uses & applications

Historically used for stone tools and weapons (arrowheads); currently used in road construction, flintlock mechanisms, and as decorative stone.

Geological facts

Flint was the primary technology for early humans; when struck against steel or pyrite, it produces sparks due to the friction oxidizing the metal particles.

Field identification & locations

Identify by its characteristic curved, shell-like (conchoidal) fractures and sharp edges. It is extremely common in the chalk downs of England and Northern Europe.