sedimentary
Chert (with potential fossil inclusion)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: tan, grey, and reddish-brown (likely due to iron oxidation), Luster: waxy to dull, Structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: tan, grey, and reddish-brown (likely due to iron oxidation), Luster: waxy to dull, Structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation from groundwater within limestone or chalk beds. Often Paleozoic or Mesozoic in age.
Uses & applications
Historically used for making sharp tools like arrowheads; currently used as road aggregate or for lapidary items.
Geological facts
Chert is so hard it can scratch glass. It was one of the first materials used by early humans for fire-starting and tool-making due to its predictable breaking patterns (conchoidal fracture).
Field identification & locations
Identify by its smooth, waxy texture and sharp, shell-like edges when broken. Commonly found in sedimentary basins and stream beds. This specimen appears to contain a trace fossil or mineral replacement of biological material.
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