sedimentary
Chert (Jasper)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs), Color: brown, tan, and reddish, Luster: dull to waxy, Structure: cryptocrystalline, Fracture: conchoidal, Specific Gravity: 2.58-2.91
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs), Color: brown, tan, and reddish, Luster: dull to waxy, Structure: cryptocrystalline, Fracture: conchoidal, Specific Gravity: 2.58-2.91
Formation & geological history
Formed via the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. The distinct coloration is due to iron impurities.
Uses & applications
Historically used for stone tools; currently used as a decorative stone, in lapidary work (jewelry), and occasionally in industrial abrasives.
Geological facts
This specimen displays 'picture-like' patterns often associated with Jasper. Chert has been used by humans for thousands of years to create sharp-edged blades and arrowheads due to its conchoidal fracturing.
Field identification & locations
Identify by its hardness (scratches glass), waxy luster on fresh breaks, and smooth, curved fracture surfaces. Commonly found in nodules or bedded layers within limestone or dolomite.
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