Chert (Flint variety)

Physical Properties

Hardness: 7 (Mohs), Color: Dark grey to black, Luster: Waxy to dull, Crystal structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific gravity: 2.65

Formation & Geological History

Formed through the accumulation of siliceous remains of marine organisms (like diatoms or radiolarians) or chemical precipitation from silica-rich fluids in limestone beds. Geological age varies from Precambrian to Cenozoic.

Uses & Applications

Historically used for making stone tools (arrowheads, knives), striking fire, and flintlock firearms. Currently used as a gemstone (jaspers), construction aggregate, and in road surfacing.

Geological Facts

Flint was one of the first materials traded by early humans. When struck against steel, it creates sparks due to the high hardness and friction, making it a pivotal survival tool for millennia.

Field Identification & Locations

Identify by its characteristic conchoidal fracture (smooth, curved surfaces like glass) and its ability to scratch glass. Commonly found in nodules within limestone or chalk deposits. Collectors look for unique banding or colors.

Identified on: 5/10/2026

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