sedimentary
Riverstone Jasper (Chert variant)
Silicon Dioxide (SiO2) with impurities
Hardness: 6.5-7 on Mohs scale. Color: Muted olive green, brown, and black. Luster: Waxy to dull. Crystal structure: Microcrystalline (trigonal). Cleavage: None (conchoidal fracture). Specific Gravity: 2.5-2.9.
- Hardness
- 6
- Color
- Muted olive green, brown, and black
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Muted olive green, brown, and black. Luster: Waxy to dull. Crystal structure: Microcrystalline (trigonal). Cleavage: None (conchoidal fracture). Specific Gravity: 2.5-2.9.
Formation & geological history
Formed from the accumulation of microcrystalline quartz or radiolarian remains in marine environments, subsequently subjected to tumble-polishing in river beds over thousands of years.
Uses & applications
Commonly used for decorative landscaping, jewelry (beads and cabochons), and as smooth 'worry stones' in holistic practices.
Geological facts
Jasper is an opaque variety of chalcedony. The specific coloration in this specimen is likely due to high iron or chlorite content trapped during the depositional process.
Field identification & locations
Identify in the field by its high hardness (it cannot be scratched by a steel knife), smooth water-worn texture, and lack of visible grains. Frequently found in stream beds and coastal gravel deposits.
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