sedimentary

Banded Flint / Chert

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Black with white or cream bands; Luster: Waxy to vitreous; Structure: Microcrystalline (Cryptocrystalline); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Black with white or cream bands
Luster: Waxy to vitreous

Identified March 28, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the accumulation of siliceous remains of marine organisms (like diatoms or radiolarians) or chemical precipitation from silica-rich fluids. Often found as nodules within limestone or chalk beds, frequently dating from the Cretaceous period.

Uses & applications

Historically used for stone tools and fire-starting. Currently used in jewelry (decorative cabochons), construction (road metal), and as a traditional sparking material in survival kits.

Geological facts

Flint was the primary source of weaponry for Stone Age humans. When struck against carbon steel, it produces hot sparks due to its extreme hardness and sharp edges. Banded varieties like this are often referred to as 'striped flint' or 'zebra flint'.

Field identification & locations

Identify in the field by its distinct conchoidal (shell-like) fracture patterns and ability to scratch glass. It is commonly found in chalk cliffs (e.g., Dover) or as river-tumbled pebbles. Collectors should look for sharp edges and distinct color banding.