sedimentary
Chert (Flint)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Gray, black, brown, or tan; Luster: Waxy to dull; Crystal structure: Hexagonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Gray, black, brown, or tan
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Gray, black, brown, or tan; Luster: Waxy to dull; Crystal structure: Hexagonal (microscopic); 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 or groundwater environments. Found in limestone or chalk beds.
Uses & applications
Historically used for stone tools (arrowheads, knives). Today used in road construction, stone age replicas, and flint-striking fire starters.
Geological facts
Flint is a variety of chert that was essential to human survival for millennia because it breaks with incredibly sharp edges and creates sparks when struck against iron or steel.
Field identification & locations
Identify by its waxy luster, smoothness, and distinctive shell-like (conchoidal) fracture. Commonly found in nodules within limestone formations or as river pebbles.
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