sedimentary
Chert (with possible fossils)
Microcrystalline quartz (SiO2)
Hardness: 6.5-7 (Mohs scale), Color: tan, grey, or off-white with waxy luster. Dense, microcrystalline structure with conchoidal fracture patterns.
- Hardness
- 6
- Color
- tan, grey, or off-white with waxy luster
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: tan, grey, or off-white with waxy luster. Dense, microcrystalline structure with conchoidal fracture patterns.
Formation & geological history
Formed through the accumulation of silica in marine environments, often replacing calcium carbonate in limestone. Its geological age can range from Precambrian to Cenozoic.
Uses & applications
Historically used for stone tools and fire-starting (flint). Currently used as an aggregate in construction or as road metal; decorative landscape gravel.
Geological facts
This specimen appears to be a stream-worn or weathered chert nodule containing circular impressions that may be crinoid stem fragments or trace fossil molds.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and waxy luster. Found globally in limestone formations and alluvial deposits. Search for fossils on weathered surfaces.
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