sedimentary

Flint or chert fragment

Microcrystalline quartz (SiO₂), commonly chalcedony with possible iron-oxide impurities

AI-generated identification · may be incorrect

Typically Mohs 6.5–7, dark gray to brown, waxy or dull luster, very fine-grained with no visible crystals or cleavage; density about 2.6 g/cm³. The sharp, curved conchoidal fracture and contrasting weathered surface are characteristic.

Identified August 16, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica replaces carbonate sediment or accumulates as biogenic silica in sedimentary rocks, commonly during the Cretaceous or younger geological periods. The blue-gray surface may reflect weathering, patination, or lighting rather than a separate mineral.

Uses & applications

Useful historically for cutting tools, arrowheads, and fire-starting; today it is mainly a lapidary, educational, or collectible material. Value is generally low unless it has unusual color, provenance, or archaeological significance.

Geological facts

Flint is a hard variety of chert that fractures into exceptionally sharp edges. It can produce sparks against steel, though this specimen’s apparent edge and color are insufficient to confirm that test.

Field identification & locations

Identify it by testing glass-scratching hardness, observing conchoidal fracture, and checking for a noncrystalline waxy interior; avoid destructive testing if archaeological origin is possible. Common in chalk, limestone, and other sedimentary formations worldwide.