sedimentary
Chert (Jasper)
Silicon Dioxide (SiO2)
Hardness: 6.5-7.0 (Mohs). Color: Deep red, maroon, and dark purple. Luster: Dull to waxy. Structure: Microcrystalline/Cryptocrystalline. Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Deep red, maroon, and dark purple
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7.0 (Mohs). Color: Deep red, maroon, and dark purple. Luster: Dull to waxy. Structure: Microcrystalline/Cryptocrystalline. Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or volcanic environments, often during the Proterozoic or Paleozoic eras.
Uses & applications
Historically used for stone tools due to sharp edges; currently used for lapidary work, jewelry (tumbled stones), and decorative landscaping.
Geological facts
Dark purple and red varieties are often specifically referred to as jasper. These stones are extremely durable and are often found as smooth pebbles in riverbeds or beaches after centuries of water erosion.
Field identification & locations
Identify by its hardness (cannot be scratched by a steel knife) and its smooth, shell-like (conchoidal) fracture surfaces. Common in river gravels and ancient sedimentary basins.
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