sedimentary
Chert (Flint/Jasper variety)
Microcrystalline quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, beige, or white with waxy luster; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan, beige, or white with waxy luster
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, beige, or white with waxy luster; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the precipitation of silica from groundwater or the accumulation of siliceous skeletal remains (diatoms, radiolaria) in deep-sea environments. It often occurs as nodules in limestone or chalk beds.
Uses & applications
Historically used for stone tools and weapons due to its sharp edges; modernly used as a decorative stone, in jewelry (as jasper), or as a source of silica.
Geological facts
Chert has been used by humans for hundreds of thousands of years to create arrowheads and scrapers because it produces extremely sharp, glass-like edges when struck.
Field identification & locations
Look for a smooth, waxy surface and a distinctive 'shell-like' curved fracture pattern (conchoidal). It is commonly found in stream beds or eroded out of sedimentary rock layers.
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Cone-in-cone structure (Secondary Sedimentary Structure)
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Chert Breccia
Brecciated Chert (Microcrystalline Silica)
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