(from calce), in Latin called creta, a species of carbonate of lime, found abundantly in Britain, France, Norway, and other parts of Europe. The island of Candia is said to have received its ancient name of Crete from the quantity of chalk found there. Chalk is used as an anti-acid; and from the readiness with which it imbibes liquids, it is much employed as an absorbent. When powdered and freed from gritty particles by washing, it forms the substance called whitening, or Spanish white, used to polish metallic utensils and glass. It is simply prepared as follows: mix chalk that has been well triturated with a large quantity of water, allow the silicious and ferruginous particles to subside, and then decant the supernatant fluid into a very fine sieve or linen bag, where the whitening will be deposited.

Black Chalk, a mineral used by artists for drawing. It is a variety of bituminous slate, the schiste-graphique of Hailly.

French Chalk, steatite or soapstone, a hydrated silicate of magnesia and alumina. It occurs of several colours, as white, brown, green, &c.; and is used in the preparation of crayons; the manufacture of porcelain, for polishing marble, and as the basis of certain cosmetic powders.

Red Chalk is an indurated clayey ochre used for similar purposes. It is reddele, or earthy clay-ironstone of the mineralogist.

Chalk-Formation. See Geology.

Chalk Stones, the name given to the concretions which occur in the joints of persons who have long suffered from gout. These consist of urate of ammonia, but were once supposed to be of a chalky nature, and thence acquired the above name.