sedimentary

Chert (likely flint)

Microcrystalline quartz (SiO₂), variety chert; flint is a dark chert variety

AI-generated identification · may be incorrect

Opaque, gray-brown with a waxy to dull luster and irregular, sharp edges; Mohs hardness about 7, no cleavage, and a fine-grained structure. The image suggests a small naturally broken fragment, but identification is provisional from appearance alone.

Identified October 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica precipitates or replaces material in sedimentary deposits, commonly limestone or chalk. Chert occurs in rocks of many geological ages.

Uses & applications

Historically used for sharp tools and fire-starting; today it is collected and occasionally used in decorative stonework.

Geological facts

Chert breaks with a curved, shell-like conchoidal fracture, producing sharp edges; this made flint valuable for prehistoric tools.

Field identification & locations

Look for hardness sufficient to scratch glass, a smooth waxy-looking fracture surface, and no visible grains. Found worldwide in sedimentary formations; the specimen’s exact locality cannot be determined from the image.