sedimentary

Chert (Flint)

Chert (SiO2)

Hardness: 7 Mohs; Color: Tan, beige, and white banding; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.5-2.8

Hardness: 7 Mohs
Color: Tan, beige, and white banding
Luster: Waxy to dull

Identified June 14, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs; Color: Tan, beige, and white banding; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.5-2.8

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments; commonly found in limestone or chalk beds.

Uses & applications

Historically used for stone tools and weapons (arrowheads); currently used in road construction, landscaping, and sometimes as a flux in glass making.

Geological facts

Chert has been used by humans for millions of years because its conchoidal fracture creates extremely sharp edges; it is chemically identical to quartz but with a microcrystalline structure.

Field identification & locations

Identify by its smooth, waxy feel and sharp, curved edges when broken. It is harder than steel and will scratch glass. Found globally in sedimentary basins.