sedimentary

Chert (Chert Nodule)

Microcrystalline quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs; Color: Grey, brown, white; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 Mohs
Color: Grey, brown, white
Luster: Waxy to dull

Identified May 3, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs; Color: Grey, brown, white; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed by the accumulation and diagenesis of silica-rich organic remains or chemical precipitation within marine or land-based sedimentary layers like limestone or chalk. Many date from the Paleozoic or Mesozoic eras.

Uses & applications

Used historically for stone tools (flintknapping), as an industrial abrasive, or as decorative gravel. Higher-grade colorful varieties are used in lapidary work.

Geological facts

Flint is a variety of chert. Because of its conchoidal fracture, it was the primary material used by prehistoric humans to create sharp edges for arrowheads and scrapers.

Field identification & locations

Identify by its 'shell-like' curved fracture surfaces and its ability to scratch glass. Commonly found as nodules within limestone outcrops or along riverbeds and beaches.