sedimentary
Chert (Red Jasper variant)
Silicon Dioxide (SiO2) with iron oxide inclusions
Hardness: 6.5-7 (Mohs); Color: Deep red, brown, and tan; Luster: Dull to waxy; Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 6
- Color
- Deep red, brown, and tan
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Deep red, brown, and tan; Luster: Dull to waxy; Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich microfossils or chemical precipitation from silica-rich fluids within sedimentary rock layers. Often associated with ancient marine environments.
Uses & applications
Historically used for stone tools (arrowheads/scrapers) due to sharp edges; currently used for lapidary work, jewelry, and as ornamental landscaping stone.
Geological facts
Jasper has been used by humans for thousands of years. Its name is derived from the Greek word 'iaspis', meaning spotted stone. It is a common component of Banded Iron Formations.
Field identification & locations
Identify in the field by its smooth, shell-like (conchoidal) fracture surfaces and its inability to be scratched by a steel knife. Found globally in sedimentary basins and riverbeds.
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