sedimentary

Flint Nodule

Chert (Cryptocrystalline Quartz, SiO2)

Hardness: 7 on Mohs scale; Color: Tan/brown rind with lighter grey-white core visible at edge; Luster: Waxy to dull on rind, vitreous/greasy on fresh fracture; Fracture: Conchoidal; Structure: Microcrystalline/Cryptocrystalline

Hardness: 7 on Mohs scale
Color: Tan/brown rind with lighter grey-white core visible at edge
Luster: Waxy to dull on rind, vitreous/greasy on fresh fracture

Identified July 25, 2026More sedimentary →

Explore Flint Nodule in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed as secondary chemical precipitates within limestone or chalk deposits through the replacement of calcium carbonate by silica derived from dissolved sponge spicules and radiolarians.

Uses & applications

Historically used for stone tools (arrowheads, blades) and starting fires (striking against steel). Today used as aggregate, decorative landscaping, and by flintknappers.

Geological facts

Flint breaks with extremely sharp conchoidal edges, which were essential for prehistoric stone tools. Nodules often feature a distinctive weathered outer cortex or rind surrounding a darker interior.

Field identification & locations

Identified by its hard, fine-grained texture, light outer rind, and conchoidal fracture pattern. Widely found in chalk beds and marine sedimentary deposits across Europe and North America.

Other sedimentary specimens

See all

Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary

Sedimentary Sandstone

Arenite (Sedimentary Rock)

sedimentary

Fossiliferous Concretion

Septarian Concretion containing Brachiopods/Crinoids

fossil

Shale

Shale (clastic sedimentary rock)

sedimentary

Shale fragment

Shale (clay mineral rich sedimentary rock)

sedimentary

Shale / Mudstone

Sedimentary rock (Claystone / Mudstone / Shale)

sedimentary