sedimentary
Chert (Jasper)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 Mohs. Color: Yellow-brown to tan with dark inclusions. Luster: Dull to waxy. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Yellow-brown to tan with dark inclusions
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 Mohs. Color: Yellow-brown to tan with dark inclusions. Luster: Dull to waxy. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the accumulation of silica-rich microfossils or precipitation from silica-rich fluids in sedimentary basins. Often found in nodules or bedded deposits.
Uses & applications
Historical use for tools and weapons due to its sharp edges; currently used for lapidary work, jewelry, and as decorative stone.
Geological facts
This specimen shows the typical waxy luster and conchoidal fracture patterns characteristic of silica-rich sedimentary rocks. Chert was one of the first materials used by early humans to create arrowheads.
Field identification & locations
Identify by its hardness (scratches glass) and smooth, shell-like fracture surfaces. Frequently found in riverbeds or limestone outcrops.
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