sedimentary

Chert

Microcrystalline silica (SiO2)

Hardness: 6.5-7 (Mohs); Color: tan, grey, buff; Luster: waxy to dull; Structure: microcrystalline; Fracture: conchoidal; Gravity: 2.6

Hardness: 6
Color: tan, grey, buff
Luster: waxy to dull

Identified June 2, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs); Color: tan, grey, buff; Luster: waxy to dull; Structure: microcrystalline; Fracture: conchoidal; Gravity: 2.6

Formation & geological history

Formed by the precipitation of silica-rich fluids within sedimentary environments, often replacing organic material or carbonate rocks. Typical age ranges from Precambrian to Holocene.

Uses & applications

Historically used for making stone tools (arrowheads). Today used as road base material and occasionally as an ornamental garden stone.

Geological facts

Chert and flint are often used interchangeably, but flint usually refers specifically to dark varieties found in chalk. It was one of the first minerals used by early humans for tools because of its sharp edges.

Field identification & locations

Identify by its hardness (scratches glass), waxy appearance, and conchoidal (shell-like) fracture patterns. Found globally in limestone and dolomite beds.