sedimentary
Chalk
Calcium Carbonate (CaCO3)
AI-generated identification · may be incorrectHardness 1 on Mohs scale, white or grey color, earthy luster, microcrystalline structure, poor cleavage, specific gravity 1.9-2.7.
Identified More sedimentary →
Explore Chalk in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness 1 on Mohs scale, white or grey color, earthy luster, microcrystalline structure, poor cleavage, specific gravity 1.9-2.7.
Formation & geological history
Formed from the accumulation of microscopic calcareous shells of marine organisms like coccolithophores during the Cretaceous period.
Uses & applications
Used in agriculture for soil conditioning, manufacturing lime, whitening agents, and traditional writing chalk.
Geological facts
Famous deposits include the White Cliffs of Dover, formed millions of years ago in shallow seas.
Field identification & locations
Identified by its soft, crumbly texture and vigorous effervescence when treated with dilute hydrochloric acid.
More like this
Other sedimentary specimens
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
fossil
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone
Arenite
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary