sedimentary
Chert (Red Jasper)
Microcrystalline Quartz (SiO2)
Hardness: 7 Mohs scale; Color: Red, brown, earthy orange; Luster: Dull to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
- Hardness
- 7 Mohs scale
- Color
- Red, brown, earthy orange
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 Mohs scale; Color: Red, brown, earthy orange; Luster: Dull to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
Formation & geological history
Formed via the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. It can occur as nodules in limestone or as bedded deposits. Geological age ranges from Precambrian to Cenozoic.
Uses & applications
Historical use for stone tools (lithics) due to sharp fracture edges. Modern use in jewelry (as Jasper), lapidary art, and occasionally as a source for industrial silica.
Geological facts
This specimen shows evidence of conchoidal (shell-like) fracturing, which is the same property that allowed ancient humans to knap it into arrowheads and scrapers. Red varieties get their color from iron oxide inclusions.
Field identification & locations
Identify by its extreme hardness (scratches glass), waxy feel on smooth surfaces, and curved, glass-like fracture planes. Common in sedimentary basins worldwide. This specific piece mimics a preform or flake from lithic reduction.
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