Chalk n.
 1. Min. A soft, earthy substance, of a white, grayish, or yellowish white color, consisting of calcium carbonate, and having the same composition as common limestone.
 2. Fine Arts Finely prepared chalk, used as a drawing implement; also, by extension, a compound, as of clay and black lead, or the like, used in the same manner. See Crayon.
 Black chalk, a mineral of a bluish color, of a slaty texture, and soiling the fingers when handled; a variety of argillaceous slate.
 By a long chalk, by a long way; by many degrees. [Slang] --Lowell.
 Chalk drawing Fine Arts, a drawing made with crayons. See Crayon.
 Chalk formation. See Cretaceous formation, under Cretaceous.
 Chalk line, a cord rubbed with chalk, used for making straight lines on boards or other material, as a guide in cutting or in arranging work.
 Chalk mixture, a preparation of chalk, cinnamon, and sugar in gum water, much used in diarrheal affection, esp. of infants.
 Chalk period. Geol. See Cretaceous period, under Cretaceous.
 Chalk pit, a pit in which chalk is dug.
 Drawing chalk. See Crayon, n., 1.
 French chalk, steatite or soapstone, a soft magnesian mineral.
 Red chalk, an indurated clayey ocher containing iron, and used by painters and artificers; reddle.


 2. Geol. Of, pertaining to, or designating, the period of time following the Jurassic and preceding the Tertiary, generally given as from 144 million years b. p. to 65 million years b. p..  Also called Cre·tac·ic.
 Cretaceous acid, an old name for carbonic acid.
 Cretaceous formation Geol., the series of strata of various kinds, including beds of chalk, green sand, etc., formed in the Cretaceous period; -- called also the chalk formation. See the Diagram under Geology.
 Cretaceous period Geol., the time in the latter part of the Mesozoic age during which the Cretaceous formation was deposited, and at the end of which the dinosaurs died out.  See Cretaceous.

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 Cretaceous period
      n : from 135 million to 63 million years ago; end of the age of
          reptiles; appearance of modern insects and flowering
          plants [syn: Cretaceous]