sedimentary
Flint (Chert variant)
Silica (SiO2) - Microcrystalline Quartz
Hardness: 7 on Mohs scale; Color: Gray, black, or dark brown with a waxy luster; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.
- Hardness
- 7 on Mohs scale
- Color
- Gray, black, or dark brown with a waxy luster
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Physical properties
Hardness: 7 on Mohs scale; Color: Gray, black, or dark brown with a waxy luster; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.
Formation & geological history
Formed as nodules in sedimentary rocks like chalk and limestone through the precipitation of silica from groundwater. Most specimens are from the Cretaceous or Jurassic periods.
Uses & applications
Historically used for making stone tools and starting fires (flint and steel). Currently used in road construction, ceramics, and as decorative gravel.
Geological facts
Flint was a vital resource for prehistoric humans who shaped it into arrowheads and knives. It produces sparks when struck against steel due to microscopic fragments of iron heating up fast.
Field identification & locations
Identifiable by its conchoidal (shell-like) fracture patterns and sharp edges when broken. Commonly found in coastal chalk cliffs or riverbeds across Europe and North America.
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Cone-in-cone structure (Secondary Sedimentary Structure)
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