sedimentary
Chert / Jasper
Silicon Dioxide (SiO2)
Hardness: 6.5-7 (Mohs); Color: Gray-green with reddish inclusions; Luster: Waxy to dull; Structure: Microcrystalline quartz; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 6
- Color
- Gray-green with reddish inclusions
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Gray-green with reddish inclusions; Luster: Waxy to dull; Structure: Microcrystalline quartz; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed from the accumulation of silica-rich microfossils or chemical precipitation in ancient marine environments or as replacements in limestone beds.
Uses & applications
Historical use for sharp tools and weapons; modern use in jewelry (as jasper), landscaping, and as a durable abrasive.
Geological facts
Chert is one of the most common materials used by early humans for lithic tools (arrowheads/knives) due to its conchoidal fracture pattern which creates razor-sharp edges.
Field identification & locations
Look for a microcrystalline texture that cannot be scratched by a steel knife and exhibits smooth, curved 'shell-like' breaks. Commonly found in riverbeds and sedimentary basins worldwide.
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Chert Breccia
Brecciated Chert (Microcrystalline Silica)
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