sedimentary

Chert (Flint variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Gray, black, or brown; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Gray, black, or brown
Luster: Waxy to dull

Identified May 16, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Gray, black, or brown; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through the accumulation of siliceous remains of microscopic organisms (like diatoms or radiolarians) or by chemical precipitation from silica-rich fluids in limestone/chalk beds.

Uses & applications

Historically used for stone tools and weapons due to sharp edges; currently used as a gemstone (lapis-like), in road construction, and for fire-starting strikers.

Geological facts

Flint was the primary material for the Stone Age 'industry'. It produces sparks when struck against steel, which led to its use in flintlock firearms.

Field identification & locations

Identify by its smooth, shell-like (conchoidal) fracture surfaces and its ability to scratch glass. Commonly found as nodules in limestone or as river pebbles.