Chert (Flint)

Physical Properties

Hardness: 7; Color: Gray, brown, tan; 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 microfossils or chemical precipitation in sedimentary basins. Often found as nodules within limestone or chalk beds.

Uses & Applications

Historical tool-making (arrowheads, scrapers), primitive fire starting, construction aggregate, and lapidary use for tumbling or polishing.

Geological Facts

Flint is a variety of chert that was essential to human survival for millennia due to its ability to produce sharp edges and sparks. It's often associated with the Stone Age.

Field Identification & Locations

Identify by its waxy texture and sharp, shell-like (conchoidal) fractures. Found in riverbeds, limestone quarries, and coastal chalk cliffs.

Identified on: 5/19/2026

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