sedimentary
Flint / Chert
Silicon dioxide (SiO2)
AI-generated identification · may be incorrectHardness of 7 on the Mohs scale, waxy or vitreous luster, conchoidal fracture, opaque to translucent, colors range from grey, white, brown, to reddish-brown due to impurities.
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Physical properties
Hardness of 7 on the Mohs scale, waxy or vitreous luster, conchoidal fracture, opaque to translucent, colors range from grey, white, brown, to reddish-brown due to impurities.
Formation & geological history
Formed diagenetically as nodules or concretionary masses in sedimentary rock, such as chalk or limestone, through the replacement of calcium carbonate by silica-rich solutions during the Cretaceous period and other geological epochs.
Uses & applications
Historically used for making stone tools, weapons, and fire-starting (strike-a-light). Currently used in decorative landscaping, road construction, and abrasive grit.
Geological facts
Flint is a hard, tough variety of microcrystalline quartz. Prehistoric humans heavily favored it for knapping sharp-edged tools due to its predictable conchoidal fracture.
Field identification & locations
Easily identified by its conchoidal fracture, waxy luster, and ability to scratch glass (hardness 7). Commonly found weathered out of chalk cliffs along coastlines and riverbeds.
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Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone or Siltstone
Arenite (if sandstone)
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Sandstone
Arenite
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Shale
Shale (clastic sedimentary rock)
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Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary