sedimentary

Chert (likely brown flint)

Microcrystalline quartz (SiO₂), commonly termed chert or flint

AI-generated identification · may be incorrect

Typically Mohs 6.5–7; opaque brown with a dull to waxy surface and conchoidal fracture. Composed of extremely fine quartz crystals, so individual crystals are not visible; the pictured piece may be naturally weathered or worked.

Identified October 12, 2026More sedimentary →

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Physical properties

Formation & geological history

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

Uses & applications

Historically used for cutting tools and sparks; today collected and sometimes fashioned into ornaments or lapidary pieces.

Geological facts

Chert can fracture into sharp-edged flakes, making it valuable to prehistoric toolmakers.

Field identification & locations

Look for a very hard, fine-grained surface and curved, shell-like fracture; common in sedimentary terrains worldwide. The image alone cannot confirm chert or establish whether the piece is worked.