sedimentary

Chert (Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Gray, black, brown, or tan; Luster: Waxy to dull; Crystal structure: Hexagonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Gray, black, brown, or tan
Luster: Waxy to dull

Identified April 6, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Gray, black, brown, or tan; Luster: Waxy to dull; Crystal structure: Hexagonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed from the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation in marine or groundwater environments. Found in limestone or chalk beds.

Uses & applications

Historically used for stone tools (arrowheads, knives). Today used in road construction, stone age replicas, and flint-striking fire starters.

Geological facts

Flint is a variety of chert that was essential to human survival for millennia because it breaks with incredibly sharp edges and creates sparks when struck against iron or steel.

Field identification & locations

Identify by its waxy luster, smoothness, and distinctive shell-like (conchoidal) fracture. Commonly found in nodules within limestone formations or as river pebbles.