sedimentary
Chert / Jasper
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 Mohs; Color: Brown, red, and dark grey; Luster: Dull to waxy; Structure: Microcrystalline/cryptocrystalline; Fractures with conchoidal (shell-like) curves.
- Hardness
- 6
- Color
- Brown, red, and dark grey
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 Mohs; Color: Brown, red, and dark grey; Luster: Dull to waxy; Structure: Microcrystalline/cryptocrystalline; Fractures with conchoidal (shell-like) curves.
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. This specimen shows iron staining (red/brown) and high silica content.
Uses & applications
Historically used for stone tools and weapons due to its sharp edges; currently used as decorative stone, in jewelry (when high quality), and as road ballast.
Geological facts
Chert was one of the most important minerals for early humans, used to create arrowheads, scrapers, and fire-starting tools because it sparks when struck against steel.
Field identification & locations
Look for a smooth, waxy texture and sharp, curved edges where broken. It cannot be scratched by a steel pocket knife. Found globally in limestone formations and riverbeds.
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