sedimentary
Chert (Flint)
Chert (Microcrystalline Quartz, SiO2)
Hardness: 7 on Mohs scale; Color: typically grey, black, or brown; Luster: waxy to dull; Structure: microcrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.65.
- Hardness
- 7 on Mohs scale
- Color
- typically grey, black, or brown
- Luster
- waxy to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically grey, black, or brown; Luster: waxy to dull; Structure: microcrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.65.
Formation & geological history
Formed by the accumulation of siliceous remains of marine organisms (like diatoms or radiolarians) or through the precipitation of silica in groundwater within limestone or chalk beds.
Uses & applications
Historically used for stone tools and weapons; currently used in construction aggregate, road surfacing, and as a starting material for flint-striking fire starters.
Geological facts
Flint is a variety of chert that was essential to human evolution for creating sharp-edged tools and sparks for fire. It produces a glass-like conchoidal fracture which allows for precision knapping.
Field identification & locations
Identified by its extreme hardness (scratches glass), waxy texture, and sharp curved edges when broken. Commonly found in nodules within limestone or as river pebbles.
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