sedimentary
Chert (Flint Nodules)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 (Mohs). Color: Gray, tan, white. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Gray, tan, white
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs). Color: Gray, tan, white. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).
Formation & geological history
Forms in sedimentary environments, often through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation within limestone or chalk beds.
Uses & applications
Historically used for stone tools and starting fires (striking steel). Modernly used in construction aggregate and as a collector's specimen.
Geological facts
Flint is a variety of chert that occurs primarily in chalk and marly limestone. It was the primary material for spearheads and arrowheads in prehistoric times due to its sharp conchoidal edges.
Field identification & locations
Identify by its waxy luster, hardness (it will scratch glass), and its distinctive curved (conchoidal) fracture planes when broken. Often found in chalk cliffs or as river pebbles.
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