sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Brown, tan, or grey; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Brown, tan, or grey
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Brown, tan, or grey; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed via the accumulation of siliceous remains of organisms (like diatoms or radiolaria) or through chemical precipitation of silica-rich fluids in sedimentary rock layers such as limestone.
Uses & applications
Historically used for stone tools and starting fires; currently used in construction aggregate and occasionally as a gemstone in tumbled forms.
Geological facts
Flint was the primary material for the Stone Age technology due to its ability to split into thin, razor-sharp edges. It produces sparks when struck against steel.
Field identification & locations
Identify by its smooth, waxy surface and its characteristic 'shell-like' conchoidal fracture patterns. Found globally in nodules within chalk or limestone beds.
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Chert Breccia
Brecciated Chert (Microcrystalline Silica)
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