A red pigment extracted from the root of the madder plant (Rubia tinctorum). It has been used in India, Persia, and Egypt since antiquity, mainly as a dye for wool. Natural madder is a mixture of different colorants, the most important being alizarin. Alizarin was synthesized in 1871, and the synthetic colorant has largely replaced madder in dye, although natural madder is still used to make artists’ paints. Web resource here.