Cinnabar, mineral consisting of mercuric sulfide (HgS), the principal commercial source of mercury. It is bright red in color, crystallizes in the hexagonal system (see Crystal), and has perfect prismatic cleavage. The hardness of cinnabar is 2.5, and the specific gravity is 8.10. The mineral is comparatively rare and usually occurs in volcanic vein deposits in sedimentary rocks. Important deposits of cinnabar are found in Spain, Italy, Mexico, and in California and Nevada in the United States. Artificial cinnabar, made from a mixture of sulfur and mercury, is used as the red pigment called vermilion.