sedimentary
Chert (Flint)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 Mohs; Color: Brown, tan, and dark gray; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); SG: 2.65
- Hardness
- 6
- Color
- Brown, tan, and dark gray
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 Mohs; Color: Brown, tan, and dark gray; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); SG: 2.65
Formation & geological history
Forms from the accumulation of siliceous remains of organisms or chemical precipitation in marine environments, often within limestone or chalk beds. Commonly associated with Cretaceous period formations.
Uses & applications
Historically used for stone tools and weapons (knapping); modern uses include construction aggregate, road base, and decorative landscaping.
Geological facts
Flint is a variety of chert that was essential to human survival for thousands of years because it produces a sharp edge and sparks when struck with steel.
Field identification & locations
Identify by its very smooth, seashell-like (conchoidal) fracture pattern and its ability to scratch glass. Often found as nodules or pebbles in riverbeds and coastal regions.
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