sedimentary
Chert (Jasper variety)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Brownish-red to dark grey; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
- Hardness
- 6
- Color
- Brownish-red to dark grey
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Brownish-red to dark grey; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
Formation & geological history
Formed through the accumulation of silica-rich microfossils or chemical precipitation from silica-rich fluids in sedimentary basins. Many specimens date from the Precambrian to Cenozoic eras.
Uses & applications
Commonly used as a decorative stone in landscaping, for making stone tools (historically), and occasionally as a gemstone in jewelry when it exhibits vibrant colors or patterns.
Geological facts
Chert was one of the most important materials for early humans due to its ability to split into sharp edges. Red and brown varieties are often referred to as Jasper.
Field identification & locations
Identify in the field by its smooth, waxy surface and its distinct conchoidal (shell-like) fracture pattern. It will easily scratch glass and does not react with acid.
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