sedimentary
Chert (Jasper/Chalcedony variant)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs scale), Color: tan to reddish-brown, Luster: dull to waxy, Crystal Structure: Cryptocrystalline (microscopic), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: tan to reddish-brown, Luster: dull to waxy, Crystal Structure: Cryptocrystalline (microscopic), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. This specimen likely originated as a silica-rich nodule within limestone or dolomite beds.
Uses & applications
Used historically for stone tools and weapons due to its sharp conchoidal fracture. Today used as abrasive material, decorative landscaping, and occasionally lapidary work.
Geological facts
Chert was one of the most important minerals for early humans, used to create arrowheads and scrapers. Because it is harder than steel, it can strike sparks against iron to start fires.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and its smooth, shell-like (conchoidal) breakage patterns. Commonly found in stream beds or eroded out of limestone cliffs.
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