sedimentary

Chert (Flint)

Microcrystalline Quartz (SiO2)

Hardness: 7 Mohs scale; Color: Cream, tan, and grey banding; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 Mohs scale
Color: Cream, tan, and grey banding
Luster: Waxy to vitreous

Identified June 19, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs scale; Color: Cream, tan, and grey banding; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. Often found as nodules in limestone or chalk beds.

Uses & applications

Historically used for stone tools and weapons (arrowheads); currently used in road construction, as a gemstone (jaspers/agates), and for fire-starting.

Geological facts

Chert has been used by humans for over two million years and was the primary material for the Stone Age technology due to its sharp conchoidal edges.

Field identification & locations

Identified by its extreme hardness (scratches glass), waxy texture, and shell-like (conchoidal) breaking pattern. Common in sedimentary basins worldwide.