sedimentary
Flint
SiO2 (Cryptocrystalline Quartz)
AI-generated identification · may be incorrectHardness of 7 on the Mohs scale, typically dark grey, brown, or black with a waxy to vitreous luster and conchoidal fracture.
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Physical properties
Hardness of 7 on the Mohs scale, typically dark grey, brown, or black with a waxy to vitreous luster and conchoidal fracture.
Formation & geological history
Formed through the chemical replacement of limestone or chalk by silica-rich groundwater over millions of years.
Uses & applications
Historically used for making stone tools and fire-starting; currently used in abrasives, ceramics, and lapidary arts.
Geological facts
Flint produces sparks when struck against steel due to its high hardness and brittle fracture pattern, making it vital for early firearms.
Field identification & locations
Identify by its distinct conchoidal fracture, sharp edges when broken, and ability to scratch glass. Commonly found in chalk formations worldwide.
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Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
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Sandstone or Siltstone
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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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