There are two pigments of this denomination: one falsely so called, prepared from bismuth, which turns black in sulphuretted hydrogen gas or any impure air, and is used as a cosmetic; the other, prepared from the waste of pearls and mother-of-pearl, which is exquisitely white, and of good body in water, but of little force in oil or varnish: it combines, however, with all other colours, without injuring the most delicate, and is itself perfectly permanent and innoxious; - witness Cleopatra's potation of pearls.