A well known calcarious earth, of an opake white color, soft and admitting no polish. It contains a large portion of carbonic acid, and is a subspecies of carbonate of lime. It is used as an absorbent and anti-acid. Cleaveland. Nicholson. Kirwan. Aikin. Black-chalk is a species of earth used by painters for drawing on blue paper. Red-chalk is an indurated clayey ocher used by painters and artificers.

To rub with chalk; to mark with chalk.

To manure with chalk, as land.

From the use of chalk in marking lines, the phrase to chalk out is used to signify, to lay out, draw out or describe; as, to chalk out a plan of proceeding.