sedimentary
Chert (or Petrifed Wood / Banded Flint)
Silicon Dioxide (SiO2)
Hardness 7 on Mohs scale, waxy to dull luster, conchoidal fracture, sharp edges when broken, microcrystalline quartz structure.
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Physical properties
Hardness 7 on Mohs scale, waxy to dull luster, conchoidal fracture, sharp edges when broken, microcrystalline quartz structure.
Formation & geological history
Formed through the accumulation of silica-rich biogenic sediments or chemical precipitation in marine or continental groundwater environments, often replacing organic structures or filling cavities.
Uses & applications
Used historically for stone tools, flintknapping, decorative landscaping rocks, and lapidary art.
Geological facts
Chert has been utilized since prehistoric times due to its predictable conchoidal fracture, allowing humans to fashion extremely sharp arrowheads, scrapers, and blades.
Field identification & locations
Look for smooth, waxy surfaces with sharp conchoidal fractures and a hardness capable of scratching steel. Commonly found in limestone formations, sedimentary beds, and gravel deposits.
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