Chert (Flint)

Physical Properties

Hardness: 7 on Mohs scale; Color: white, grey, brown; Luster: vitreous to waxy; Crystal structure: cryptocrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.65

Formation & Geological History

Formed from the accumulation of siliceous remains of organisms like diatoms or radiolarians, or through chemical precipitation in marine environments. Prevalent in sedimentary strata like limestone.

Uses & Applications

Historically used for stone tools and weapons (arrowheads); currently used in construction as road stone, in ceramics, and as fire-starting flints.

Geological Facts

Chert is so hard it can scratch glass and steel. It was one of the most vital materials for early humans because of its predictable fracture patterns and sharp edges.

Field Identification & Locations

Identify by its waxy texture and shell-like (conchoidal) fractures. Found worldwide in nodules or layers within sedimentary rocks. A key find for arrowhead hunters.

Identified on: 4/15/2026

Mode: Standard