Chalk

Chalk is a soft, porous limestone composed chiefly of microscopic marine plankton shells. Its fine grains and high porosity distinguish it from many other limestones.

Coccolithophore: A single-celled marine alga that produces microscopic calcium carbonate plates called coccoliths. Coccolithophores supply many of the tiny carbonate plates that accumulate to form chalk.
Marine sedimentation: The settling and accumulation of particles on the seafloor. Plankton remains settle onto the seabed before chalk beds develop.
Chalk quarrying: The extraction of chalk from surface or underground deposits. Quarrying supplies chalk for construction, cement manufacture, and industrial processing.
White Cliffs of Dover: A prominent stretch of white chalk cliffs on England’s southeastern coast. These cliffs expose thick chalk deposits formed in the Late Cretaceous.
Limestone: A sedimentary rock composed mainly of calcium carbonate. Chalk is a fine-grained, soft variety within the broader limestone family.
Coccolith: A microscopic calcium carbonate plate produced by a coccolithophore and used to build its outer covering. These plates are among chalk’s characteristic microscopic shell fragments.
Dissolution (geology): The removal of minerals into water through chemical reactions. Dissolution can remove carbonate grains and alter chalk’s pores and fractures.
Cement: A powdered binder that hardens when mixed with water and binds construction materials together. Chalk can provide carbonate feedstock for cement production.
Chalk Group: A major sequence of Upper Cretaceous chalk formations in northwestern Europe. This regional succession preserves extensive deposits of the rock.
Chert: A hard, fine-grained sedimentary rock composed chiefly of microcrystalline silica. Chert nodules can occur within chalk, but their silica composition makes them much harder.

Linked from 14 pages