sedimentary
Chert (Jasper variation)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 (Mohs); Color: Reddish-brown, earthy; Luster: Waxy to dull; Structure: Microcrystalline/Cryptocrystalline; Fracture: Conchoidal; Specific Gravity: 2.6-2.7
- Hardness
- 6
- Color
- Reddish-brown, earthy
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Reddish-brown, earthy; Luster: Waxy to dull; Structure: Microcrystalline/Cryptocrystalline; Fracture: Conchoidal; Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. Common in marine limestone beds and as nodules.
Uses & applications
Historically used for stone tools and arrowheads due to its sharp edges; currently used for lapidary work, jewelry, and as landscaping stone.
Geological facts
Chert is so durable that it often survives as pebbles in stream beds long after the surrounding rock has weathered away. It is chemically identical to quartz but contains impurities that give it color.
Field identification & locations
Identify in the field by its waxy luster, extreme hardness (can scratch glass), and smooth, shell-like (conchoidal) fracture surfaces. Commonly found in gravel pits and desert washes.
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