sedimentary

Chert or flint fragment

Microcrystalline quartz (SiO₂), commonly chalcedony

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; tan, cream, and reddish-brown coloration with a dull to waxy luster. It is very fine-grained, lacks visible crystals and cleavage, and typically shows conchoidal fracture with sharp edges.

Identified August 23, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater replaces or cements sediments, often in limestone or chalk; many specimens are Paleozoic to Cenozoic, though age depends on locality. The pictured piece may be a naturally fractured or worked fragment.

Uses & applications

Used historically for arrowheads, cutting tools, and fire-starting; today it is mainly collected or used decoratively. Quality flint and patterned chert may be fashioned into cabochons or small carvings.

Geological facts

Chert is the broader rock name, while flint usually refers to dark, dense chert associated with chalk. Freshly fractured surfaces can produce exceptionally sharp edges.

Field identification & locations

Look for a smooth waxy surface, opaque fine texture, conchoidal fracture, and glass-like sharp margins; a steel file should barely scratch it. Common in limestone, chalk, gravel deposits, and archaeological sites worldwide.