sedimentary

Flint (Chert Node)

Silicon Dioxide (SiO2)

Hardness: 7; Color: Dark grey to black; Luster: Waxy to dull; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

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

Identified June 5, 2026More sedimentary →

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Physical properties

Hardness: 7; Color: Dark grey to black; Luster: Waxy to dull; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed in sedimentary rocks like chalk or limestone through the replacement of calcium carbonate by silica-rich fluids, often beginning with organic remains.

Uses & applications

Primarily used in prehistoric times for tool-making; today used in construction (road metal), historical replication, and as a striker for fire-starting.

Geological facts

Flint was one of the most important minerals for early humans, used to create sharp edges for hunting and scrapers. It produces sparks when struck against steel due to iron oxidation.

Field identification & locations

Identify by its waxy surface and sharp, curved (conchoidal) edges when broken. Frequently found in coastal chalk cliffs and riverbeds as rounded nodules.