sedimentary
Flint
SiO2 (Microcrystalline Quartz)
AI-generated identification · may be incorrectHardness of 7 on the Mohs scale, waxy to vitreous luster, conchoidal fracture, and typically grey, brown, or black in color with no visible crystal structure.
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Physical properties
Hardness of 7 on the Mohs scale, waxy to vitreous luster, conchoidal fracture, and typically grey, brown, or black in color with no visible crystal structure.
Formation & geological history
Forms by the replacement of calcium carbonate with silica in chalk or limestone formations during the Cretaceous period.
Uses & applications
Historically used for making stone tools and fire-starting; currently used in decorative aggregates, ceramics, and abrasives.
Geological facts
Flint produces sparks when struck against steel due to its high hardness and brittle fracture, making it essential for early weaponry and fire generation.
Field identification & locations
Identify in the field by its smooth weathered cortex, sharp conchoidal edges, and ability to scratch glass easily. Commonly found embedded in chalk cliffs worldwide.
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Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
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Sandstone or Siltstone
Arenite (if sandstone)
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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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