sedimentary
Chert (Jasper/Mudstone variant)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 (Mohs); Color: Brownish-tan to earthy ocher; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 6
- Color
- Brownish-tan to earthy ocher
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Brownish-tan to earthy ocher; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich microfossils or precipitation from hydrothermal fluids in sedimentary basins. This specimen shows characteristics of a clay-rich chert or silicified mudstone common in Paleozoic to Mesozoic strata.
Uses & applications
Historically used for making stone tools due to its sharp edges; modern uses include landscaping and as a minor source of silica for industrial purposes.
Geological facts
Chert is so hard it can strike sparks against steel. It is nearly chemically inert and extremely resistant to weathering, often remaining as gravel long after surrounding limestone has dissolved.
Field identification & locations
Identify in the field by its smooth, shell-like (conchoidal) fracture pattern and its inability to be scratched by a steel knife. It is found globally in sedimentary rock outcrops.
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