sedimentary

Chert (Flint)

Chert (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: Gray, tan, white, or black; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (microscopic quartz); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 6
Color: Gray, tan, white, or black
Luster: Waxy to dull

Identified June 25, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or by chemical precipitation in marine environments. Often found as nodules in limestone or chalk beds.

Uses & applications

Historically used for stone tools and starting fires; currently used in construction aggregate, road surfacing, and as a low-cost gemstone for lapidary work.

Geological facts

Flint is a variety of chert that was essential to prehistoric humans for crafting sharp-edged arrowheads and knives due to its predictable conchoidal fracturing.

Field identification & locations

Identify by its 'shell-like' curved fractures and ability to scratch glass. Commonly found in gravel pits, stream beds, and limestone outcrops. High-quality colorful pieces are prized by flintknappers.