Research topic: chalk

chalk mineral of calcium carbonate , similar in composition to limestone, but softer. It is characteristically a marine formation and sometimes occurs in great thickness; the chief constituents of these chalk deposits are the shells of minute animals called foraminiferans . Chalk has been laid down in all periods of geologic time, but most of the best-known deposits, e.g., the cliffs of the English Channel, date from the Cretaceous period . Chalk is used in the manufacture of putty, plaster, cement, quicklime, mortar, and rubber goods and also for blackboard chalk. Harder forms are used... Read more