sedimentary

Chert (Flint nodules in limestone)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs); Color: tan, brown, or gray; Luster: waxy to vitreous; Crystal structure: cryptocrystalline; Cleavage: none; Fracture: conchoidal (shell-like curves); Specific gravity: 2.65

Hardness: 7 (Mohs)
Color: tan, brown, or gray
Luster: waxy to vitreous

Identified May 24, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs); Color: tan, brown, or gray; Luster: waxy to vitreous; Crystal structure: cryptocrystalline; Cleavage: none; Fracture: conchoidal (shell-like curves); Specific gravity: 2.65

Formation & geological history

Formed by the accumulation of siliceous remains of marine organisms (like diatoms or radiolarians) or chemical precipitation of silica within limestone or chalk beds, often during the Paleozoic or Mesozoic eras.

Uses & applications

Historically used for stone tools and weapons (arrowheads); currently used in road construction, as jewelry (when patterned or colorful), and as a sparking element in survival tools.

Geological facts

Flint is a variety of chert. When it breaks, it creates edges that are sharper than a surgeon's steel scalpel. It has been a primary material for human technology for over 2 million years.

Field identification & locations

Identify in the field by its smooth, waxy surface contrasting against a rougher chalk/limestone matrix. Look for curved, glass-like fracture surfaces. Often found in riverbeds or coastal chalk cliffs.