sedimentary

Flint (Chert)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Gray, brown, or black interior with a white exterior cortex; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Gray, brown, or black interior with a white exterior cortex
Luster: Waxy to vitreous

Identified May 7, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed as nodules in sedimentary rocks like chalk or limestone through the replacement of calcium carbonate with silica. Commonly associated with the Cretaceous period.

Uses & applications

Historically used for stone tools and starting fires; modern uses include road construction, ceramics, and as a decorative stone in jewelry or flint-knapping art.

Geological facts

Flint has a unique ability to produce sparks when struck against steel. It was the primary material for the 'Stone Age' technology, used for arrows, scrapers, and axes.