sedimentary

Chert / Flint

Silicon Dioxide (SiO₂)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: typically gray, white, or brown; Luster: waxy to dull; Crystal structure: cryptocrystalline (microscopic quartz); Cleavage: none (conchoidal fracture); Specific gravity: 2.65

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

Identified March 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation from groundwater within limestone or chalk beds. Often found in Phanerozoic age strata.

Uses & applications

Historically used for stone tools and weapons (arrowheads). Modern uses include road surfacing, flintlock mechanisms, and as decorative gemstones (jasper).

Geological facts

Chert has been used by humans for over 2 million years. When struck against steel, it creates sparks, which made it the primary ignition source for early firearms and survival tools.

Field identification & locations

Identify by its characteristic conchoidal fracture (smooth, curved surfaces like broken glass) and its ability to scratch glass. Commonly found in stream beds or eroding out of limestone outcrops.