sedimentary

Chert (Flint)

Microcrystalline Quartz (SiO2)

Hardness: 7 on Mohs scale; Color: Grey, blue-grey, brown; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 7 on Mohs scale
Color: Grey, blue-grey, brown
Luster: Waxy to vitreous

Identified June 30, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Grey, blue-grey, brown; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of siliceous remains of organisms (like diatoms or radiolarians) or by chemical precipitation from silica-rich fluids in sedimentary basins or limestone cavities.

Uses & applications

Historically used for stone tools (arrowheads, scrapers) and strike-a-lights for fire starting. Modern uses include abrasives and lapidary items.

Geological facts

Flint was one of the most important minerals for early human survival, used to create the sharpest edges known to prehistoric technology and essential for making fire.

Field identification & locations

Identify by its characteristic conchoidal (shell-like) fracture patterns and sharp edges. It is often found as nodules inside limestone or chalk beds, or as pebbles in stream beds.