sedimentary

Chert (flint) fragment

Microcrystalline quartz (SiO₂), commonly called chert or flint

AI-generated identification · may be incorrect

Typically Mohs 6.5–7; this fragment is gray-brown with a waxy to dull luster and conchoidal fracture. Its microscopic quartz crystals are too small to see; it has no obvious cleavage.

Identified October 4, 2026More sedimentary →

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Physical properties

Typically Mohs 6.5–7; this fragment is gray-brown with a waxy to dull luster and conchoidal fracture. Its microscopic quartz crystals are too small to see; it has no obvious cleavage.

Formation & geological history

Forms when silica accumulates or replaces material in sedimentary settings, often in limestone or chalk. Its exact age and locality cannot be determined from the image.

Uses & applications

Historically knapped for tools and fire-starting; today used decoratively and collected. Small, common fragments have little commercial value.

Geological facts

Sharp conchoidal edges made chert useful for prehistoric cutting tools; “flint” is a variety of chert.

Field identification & locations

Look for a hard, fine-grained texture and curved, shell-like fracture surfaces; it commonly occurs in sedimentary formations and stream gravels. The pictured piece is consistent with chert, though image identification is not definitive.