sedimentary

Chert (or Flint)

Microcrystalline or cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: Grey, brown, or tan with waxy luster. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7.

Hardness: 7 (Mohs scale), Color: Grey, brown, or tan with waxy luster
Color: Grey, brown, or tan with waxy luster

Identified May 16, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale), Color: Grey, brown, or tan with waxy luster. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7.

Formation & geological history

Formed primarily through the accumulation of siliceous remains of marine organisms (like diatoms or radiolarians) or chemical precipitation from silica-rich fluids in sedimentary basins. These specimens often date from the Precambrian to present.

Uses & applications

Historically used for stone tools and weapons (arrowheads). Modernly used as a decorative stone, in road construction, and for fire-starting (flint strikers).

Geological facts

Chert is so hard it can scratch steel. When broken, it produces a conchoidal (shell-like) fracture that creates sharp edges, which is why it was the primary material for prehistoric tools.