Information from the Getty AAT
chalk
A fine-grained limestone, or soft, earthy form of calcium carbonate; used chiefly in putty, crayons, paint, rubber products, linoleum, and as a pigment and abrasive.
History of technique in the arts, 1500-1950
A fine-grained limestone, or soft, earthy form of calcium carbonate; used chiefly in putty, crayons, paint, rubber products, linoleum, and as a pigment and abrasive.