sedimentary
Chert (Flint variety)
Silicon dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 7 Mohs; Color: Gray, tan, and dark brown; Luster: Waxy to dull; Structure: Cryptocrystalline quartz; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 Mohs
- Color
- Gray, tan, and dark brown
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 Mohs; Color: Gray, tan, and dark brown; Luster: Waxy to dull; Structure: Cryptocrystalline quartz; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of siliceous remains of marine organisms or chemical precipitation of silica-rich fluids within limestone or chalk beds. Often found in nodules.
Uses & applications
Historically used for stone tools/weapons; currently used in construction aggregate, road surfacing, and as a starting stone for fire-making.
Geological facts
Chert is so hard it can scratch steel and was the primary material for arrowheads and scrapers in prehistoric times due to its sharp, glass-like edges when broken.
Field identification & locations
Identify by its waxy appearance and conchoidal (shell-like) fracture pattern. Commonly found in riverbeds and limestone outcrops.
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