sedimentary
Flint (Chert)
Silicon Dioxide (SiO2)
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
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Physical properties
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
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.
Field identification & locations
Identify by its chalky white outer rind and glass-like, sharp interior when broken. Commonly found in coastal areas of England and northern Europe.
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