sedimentary
Chert (Flint)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: Brown, tan, or gray; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (microscopic quartz); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Brown, tan, or gray
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Brown, tan, or gray; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (microscopic quartz); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed from the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation in marine environments. Often found as nodules in limestone or chalk beds.
Uses & applications
Historically used for stone tools and starting fires (flint and steel). Currently used in road construction, as a gemstone (jaspers), and for decorative gravel.
Geological facts
Flint is a variety of chert that was the primary material for prehistoric technology, including arrowheads and knives, because it breaks into razor-sharp edges.
Field identification & locations
Identify in the field by its smooth, waxy surface and its tendency to break into curved, shell-like (conchoidal) shapes. It will scratch glass easily.
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