sedimentary

Banded Flint (Polished Stripe Flint)

Silicon Dioxide (SiO2) - variety of Chert

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: alternating bands of gray, tan, brown, and cream; Luster: vitreous to waxy when polished; Crystal structure: Cryptocrystalline; Cleavage: none (conchoidal fracture).

Hardness: 6
Color: alternating bands of gray, tan, brown, and cream
Luster: vitreous to waxy when polished

Identified March 9, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the precipitation of silica within sedimentary rock layers, often limestone or chalk. The distinct banding occurs due to rhythmic changes in the environment or water chemistry during mineral deposition, typically dating from the Cretaceous period.

Uses & applications

Primarily used in jewelry as cabochons, pendants, and beads. Historically used for tool-making (stone age) and later for strike-a-lights/fire-starting. Some industrial use as grinding media.

Geological facts

Banded flint is often called 'Striped Flint' or 'Polished Flint.' The most famous variety comes from Poland (Holy Cross Mountains), which was mined as early as the Neolithic period for ritual axes and tools.

Field identification & locations

Identify by its distinct, parallel, rhythmic banding and extreme hardness (cannot be scratched by a steel knife). Look for it in chalk-heavy regions or coastal cliff areas. It is non-porous and feels cool to the touch.