sedimentary

Chert

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Tan, beige, brown; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Tan, beige, brown
Luster: Waxy to dull

Identified July 1, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Tan, beige, brown; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).

Formation & geological history

Forms primarily as nodules or beds in sedimentary rocks through the accumulation of silica-rich organic remains or chemical precipitation. Found in various geological eras.

Uses & applications

Historically used for stone tools due to sharp edges; currently used in construction as road metal and in lapidary work for tumbled stones and cabochons.

Geological facts

Flint is a dark variety of chert. It has been used since the Stone Age for making arrowheads and spear points because of the way it fractures into sharp edges.

Field identification & locations

Identified by its waxy appearance, extreme hardness (scratches glass), and distinctive shell-like (conchoidal) fracture pattern. Common in limestone deposits.