vermilion, vivid red pigment of durable quality. It is a chemical compound of mercury and sulfur and is known as red sulfide of mercury; it was formerly obtained by grinding pure cinnabar but is now commonly prepared synthetically. Vermilion is a good pigment for protecting iron and steel and is therefore used in paints. It is commonly adulterated because of its high cost. Certain other materials are sometimes called vermilion; among them is imitation vermilion, prepared from a combination of red lead or basic lead chromate and certain other chemicals.