sedimentary

Chert / Flint

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: typically grey, brown, or white; Luster: waxy to dull; Breakage: conchoidal fracture which creates sharp edges; Structure: microcrystalline quartz.

Hardness: 7 on Mohs scale
Color: typically grey, brown, or white
Luster: waxy to dull

Identified July 18, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: typically grey, brown, or white; Luster: waxy to dull; Breakage: conchoidal fracture which creates sharp edges; Structure: microcrystalline quartz.

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or chemical precipitation from groundwater within sedimentary rock layers like limestone.

Uses & applications

Historically used for stone tools and weapons (arrowheads); currently used in road construction, as flint for fire-starting, and occasionally as an ornamental stone.

Geological facts

Flint was one of the most important minerals for early human survival, enabling the creation of sharp cutting tools and the ability to start fires reliably.

Field identification & locations

Look for a very hard, smooth-textured rock that breaks with shell-like (conchoidal) curves. It will easily scratch glass and is often found as nodules inside limestone or chalk beds.