sedimentary

Possible flint (chert) fragment

Microcrystalline quartz (SiO₂), commonly called flint when dark and nodular

AI-generated identification · may be incorrect

Dark gray to black, dull-to-waxy luster, very fine-grained and dense; Mohs hardness about 7, with no visible cleavage and conchoidal fracture. The image is consistent with a small weathered or freshly fractured fragment, though lighting limits certainty.

Identified August 16, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms by replacement or precipitation of silica in sedimentary rocks, especially chalk and limestone, commonly during the Cretaceous or other Phanerozoic periods. Flint and related chert are widespread in the Pyrenees foothills and nearby sedimentary terrains around 42.9°N, 0.1°W.

Uses & applications

Used historically for sharp tools, fire-starting, and arrowheads; today mainly collected or used as aggregate and decorative stone. This small piece has negligible commercial value.

Geological facts

A sharp, glass-like edge and curved fracture surfaces are characteristic. It may resemble dark quartzite, basalt, or slag, so a conclusive identification needs a fracture view and simple tests.

Field identification & locations

Look for conchoidal fractures, a waxy surface, extreme resistance to scratching, and a white streak or powder when abraded. Likely value is $1–$10 for a common fragment; worked or archaeological pieces can be worth much more.