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Chalk \Chalk\ (ch[add]k), n. [AS. cealc lime, from L. calx
limestone. See {Calz}, and {Cawk}.]
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.