sedimentary

Tumbled chert or flint

Microcrystalline quartz (SiO₂), commonly termed chert; dark varieties are called flint

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; olive-brown to gray, waxy/glassy luster, opaque to slightly translucent edges, and conchoidal fracture. The smooth surface indicates natural water wear or tumbling.

Identified August 31, 2026More sedimentary →

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Physical properties

Hardness about 6.5–7 Mohs; olive-brown to gray, waxy/glassy luster, opaque to slightly translucent edges, and conchoidal fracture. The smooth surface indicates natural water wear or tumbling.

Formation & geological history

Forms when silica-rich groundwater replaces or fills sedimentary material, especially limestone or chalk, producing microcrystalline quartz. Individual nodules may range from Paleozoic to Cenozoic in age.

Uses & applications

Used historically for sharp tools and fire-starting, and today as aggregate, decorative stone, and lapidary material. This specimen has modest collector value.

Geological facts

Chert commonly preserves fossils or subtle internal textures, while flint is usually a dense, dark chert associated with chalk. A fresh break produces razor-sharp edges.

Field identification & locations

Identify by its very hard, non-cleavable body, waxy appearance, and conchoidal fracture; it should scratch glass. Common sources include chalk and limestone regions worldwide, including England, Texas, Missouri, and the Great Lakes.