sedimentary
Flint
SiO2 (Microcrystalline Quartz)
AI-generated identification · may be incorrectHardness of 7 on the Mohs scale, waxy or vitreous luster, conchoidal fracture, and typically grey, brown, or tan in color.
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Physical properties
Hardness of 7 on the Mohs scale, waxy or vitreous luster, conchoidal fracture, and typically grey, brown, or tan in color.
Formation & geological history
Formed through the chemical replacement of calcium carbonate by silica-rich solutions in chalk or limestone formations during the Cretaceous period.
Uses & applications
Historically used for making stone tools and striking fire; currently used in landscaping and abrasives.
Geological facts
Flint was a vital material for early human survival due to its ability to be chipped into extremely sharp edges, known as knapping.
Field identification & locations
Identify by its distinctive conchoidal fracture, waxy luster, and high hardness that scratches glass; commonly found embedded in chalk deposits worldwide.
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Fossil-bearing concretion, possibly containing a fossil shell or other organic inclusion
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Sandstone or Siltstone
Arenite (if sandstone)
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Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
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Sandstone
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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)
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