sedimentary
Chert (Flint/Jasper)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Gray, green, brown, or white; Luster: Waxy to dull; Crystal structure: Microcrystalline/cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 6
- Color
- Gray, green, brown, or white
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Gray, green, brown, or white; Luster: Waxy to dull; Crystal structure: Microcrystalline/cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed as nodules in sedimentary rocks like limestone or as bedded deposits. It precipitates from silica-rich fluids or biological remains (diatoms/radiolarians) over millions of years.
Uses & applications
Historically used for stone tools and weapons (arrowheads); used industrially in road surfacing and as a raw material for ceramics.
Geological facts
Because of its conchoidal fracture, it breaks with sharp edges, making it the primary material for stone-age technology. It is also sparks when struck against steel.
Field identification & locations
Identify by its waxy appearance and shell-like (conchoidal) curved fractures. Common in river beds and sedimentary outcrops worldwide.
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