Chert (Flint)

Physical Properties

Hardness: 6.5-7 Mohs; Color: Gray, tan, brown with waxy luster; Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.65

Formation & Geological History

Formed by the accumulation of siliceous remains of organisms (like diatoms or radiolarians) or through chemical precipitation in marine or groundwater environments.

Uses & Applications

Historically used for stone tools and starting fires; currently used in construction aggregate and as a collector's item.

Geological Facts

Flint is a variety of chert that has been vital to human history, being the primary material for arrowheads and scrapers during the Stone Age.

Field Identification & Locations

Identify by its characteristic shell-like (conchoidal) fracture patterns and ability to scratch glass. Commonly found in limestone or chalk beds.

Identified on: 4/30/2026

Mode: Standard