sedimentary

Blue-gray flint (chert)

Microcrystalline quartz (SiO₂), a variety of chert

AI-generated identification · may be incorrect

Opaque blue-gray, rough and fractured, with a dull to slightly waxy luster; hardness about 7 Mohs and no cleavage. The small, fine-grained specimen is consistent with flint, though color alone cannot confirm identification.

Identified October 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms as silica-rich sediment or replacement of carbonate sediments, later becoming microcrystalline quartz; chert occurs in rocks of many geological ages. Its exact age and source cannot be determined from the image.

Uses & applications

Historically knapped for tools and fire-starting; today used for teaching, collecting, and occasionally decorative work.

Geological facts

Flint fractures with a curved, shell-like (conchoidal) surface and can produce sharp edges.

Field identification & locations

Look for hardness near 7, conchoidal fractures, and a waxy surface; common in chalk and limestone regions, including parts of Europe and North America. The image does not show diagnostic context or a fresh fracture.