sedimentary

Chert (Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Grey, tan, or white; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Grey, tan, or white
Luster: Waxy to dull

Identified March 6, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Grey, tan, or white; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation from fluids; typically found as nodules in limestone or chalk beds dating from the Precambrian to the present.

Uses & applications

Historically used for stone tools and arrowheads; currently used in construction aggregate, road surfacing, and as a component in certain ceramics.

Geological facts

Chert was one of the first materials used by early humans to create fire and sharp tools due to its predictable conchoidal fracturing. 'Flint' is technically a high-quality variety of chert found in chalk or marly limestone.

Field identification & locations

Identify in the field by its hardness (it will scratch glass) and its sharp, shell-like (conchoidal) breaking pattern. It is commonly found in riverbeds or eroded out of limestone outcrops worldwide.