sedimentary
Chalk
Micritic limestone (CaCO3)
AI-generated identification · may be incorrectMohs hardness 1.5-2.5, white to light gray color, earthy luster, fine-grained microcrystalline calcite structure.
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Physical properties
Mohs hardness 1.5-2.5, white to light gray color, earthy luster, fine-grained microcrystalline calcite structure.
Formation & geological history
Formed by the accumulation of calcareous shells of microscopic marine algae over millions of years during the Cretaceous period.
Uses & applications
Used in agriculture for soil conditioning, manufacturing lime, blackboard chalk, and in various industrial fillers.
Geological facts
Famous for forming the iconic White Cliffs of Dover and represents millions of years of compressed marine microfossils.
Field identification & locations
Easily identified by its soft, powdery texture and vigorous fizzing reaction when exposed to dilute hydrochloric acid.
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Fossil-bearing concretion, possibly containing a fossil shell or other organic inclusion
Calcareous concretion; exact fossil and host-rock composition are not identifiable from the image
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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
Arenite
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Shale
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Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
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