sedimentary
Jasper or Banded Chert
Silicon dioxide (SiO2) with impurities
Hardness: 6.5-7 (Mohs scale), Color: Variegated brown, grey, and cream bands, Luster: Dull to waxy, Crystal Structure: Microcrystalline (trigonal), Cleavage: None/Conchoidal fracture, Specific Gravity: 2.58-2.91
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Variegated brown, grey, and cream bands, Luster: Dull to waxy, Crystal Structure: Microcrystalline (trigonal), Cleavage: None/Conchoidal fracture, Specific Gravity: 2.58-2.91
Formation & geological history
Formed through the accumulation of silica-rich microfossils or chemical precipitation from sea water, often occurring as nodules in limestone or as distinct bedded deposits. This specimen has been tumbled or polished into an egg shape.
Uses & applications
Used primarily in lapidary work for jewelry, decorative stones, carvings, and as pocket stones for collectors.
Geological facts
Jasper is an opaque variety of chalcedony. The banding seen here often results from variations in oxygen levels or mineral impurities during the deposition process millions of years ago.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a steel knife) and its smooth, waxy surface when wet. Commonly found in riverbeds or coastal areas where erosion has exposed silica-rich veins.
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