Chalk is a very soft kind of rock or limestone. While chalk is made of shells and the skeletons of sea creatures, it's usually found above sea level in pits or quarries.

Chalk is made of the element calcium carbonite, and it has agricultural uses, as well as showing up (in tiny amounts) in both toothpaste and antacids. The kind of chalk that you use for writing on a blackboard or decorating the sidewalk was originally made from calcium carbonite, but modern writing chalk is more often made of gypsum, a related form of calcium. Chalk comes from the Latin calx, "limestone," with the Greek root khalix, "small pebble."

Definitions of chalk
  1. noun
    a soft whitish calcite
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    type of:
    a common mineral consisting of crystallized calcium carbonate; a major constituent of limestone
  2. noun
    a piece of calcite or a similar substance, usually in the shape of a crayon, that is used to write or draw on blackboards or other flat surfaces
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    drawing chalk
    colored chalks used by artists
    tailor's chalk
    chalk used by tailors to make temporary marks on cloth
    type of:
    writing implement
    an implement that is used to write
  3. verb
    write, draw, or trace with chalk
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    type of:
    represent by making a drawing of, as with a pencil, chalk, etc. on a surface
  4. noun
    a pure flat white with little reflectance
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    type of:
    white, whiteness
    the quality or state of the achromatic color of greatest lightness (bearing the least resemblance to black)
  5. noun
    an amphetamine derivative (trade name Methedrine) used in the form of a crystalline hydrochloride; used as a stimulant to the nervous system and as an appetite suppressant
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    type of:
    controlled substance
    a drug or chemical substance whose possession and use are controlled by law
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