sedimentary
Chert (Jasper variation)
Microcrystalline Quartz (SiO2)
Hardness: 6.5–7 on Mohs scale. Color: Opaque brown, reddish-brown. Luster: Dull to waxy. Crystal structure: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None (conchoidal fracture). Specific gravity: 2.6–2.7.
- Hardness
- 6
- Color
- Opaque brown, reddish-brown
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5–7 on Mohs scale. Color: Opaque brown, reddish-brown. Luster: Dull to waxy. Crystal structure: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None (conchoidal fracture). Specific gravity: 2.6–2.7.
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. Common in marine limestone beds and as nodules. Can date from the Precambrian to Cenozoic.
Uses & applications
Historically used for stone tools (knapping) due to its sharp edges. Today used as an ornamental stone, in decorative landscaping, and for lapidary work/jewelry.
Geological facts
Because of its high silica content and density, it was the primary material used by prehistoric humans to create arrowheads, scrapers, and knives. Jasper is the name specifically given to the more colorful, opaque varieties of chert.
Field identification & locations
Identify by its 'shell-like' conchoidal fracture patterns and inability to be scratched by a steel knife. Commonly found in riverbeds, glacial tills, and weathering out of limestone formations. Highly prized by flintknappers.
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