sedimentary
Chert (Flint)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Gray, brown, black, 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, brown, black, or tan
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Gray, brown, black, 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 through the precipitation of silica in groundwater within limestone or chalk beds.
Uses & applications
Used in the stone tool industry (knapping), as a starting material for fire (flint and steel), in some road construction aggregate, and as a collector specimen.
Geological facts
Flint is a variety of chert that was the most important raw material for early humans to create sharp tools and weapons like arrowheads and axes.
Field identification & locations
Identify by its characteristic conchoidal fracture (curved, shell-like breaks) and sharpness. It is harder than steel and will scratch glass easily. Found globally in sedimentary rock outcrops.
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