sedimentary

Chert (Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

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

Identified May 24, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Gray, brown, black, 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 through the precipitation of silica in groundwater within limestone or chalk beds.

Uses & applications

Used in the stone tool industry (knapping), as a starting material for fire (flint and steel), in some road construction aggregate, and as a collector specimen.

Geological facts

Flint is a variety of chert that was the most important raw material for early humans to create sharp tools and weapons like arrowheads and axes.

Field identification & locations

Identify by its characteristic conchoidal fracture (curved, shell-like breaks) and sharpness. It is harder than steel and will scratch glass easily. Found globally in sedimentary rock outcrops.