sedimentary
Chert (Brecciated or Veined)
Microcrystalline Quartz (SiO2)
Hardness 7, waxy to dull luster, conchoidal fracture, extremely fine-grained, color ranging from tan/grey to blue-grey with white quartz veining.
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Physical properties
Hardness 7, waxy to dull luster, conchoidal fracture, extremely fine-grained, color ranging from tan/grey to blue-grey with white quartz veining.
Formation & geological history
Formed from the accumulation of silica-rich microfossils or chemical precipitation in marine environments. This specific piece shows evidence of tectonic stress resulting in fractures later filled with secondary minerals.
Uses & applications
Historically used for stone tools due to sharp edges; currently used for road ballast, landscaping, and occasionally as lapidary material when colorful.
Geological facts
Chert is so durable it often survives long after other surrounding rocks have weathered away. It is often synonymous with 'flint' in common parlance.
Field identification & locations
Identify by its extreme hardness (scratches glass) and smooth, shell-like fracture surfaces. Found worldwide in sedimentary bedding planes and as nodules in limestone.
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