1911 Encyclopædia Britannica/Cinnabar
CINNABAR (Ger. Zinnober), sometimes written cinnabarite, a name applied to red mercuric sulphide (HgS), or native vermilion, the common ore of mercury. The name comes from the Greek κιννάβαρι, used by Theophrastus, and probably applied to several distinct substances. Cinnabar is generally found in a massive, granular or earthy form, of bright red colour, but it occasionally occurs in crystals, with a metallic adamantine lustre. The crystals belong to the hexagonal system, and are generally of rhombohedral habit, sometimes twinned. Cinnabar presents remarkable resemblance to quartz in its symmetry and optical characters. Like quartz it exhibits circular polarization, and A. Des Cloizeaux showed that it possessed fifteen times the rotatory power of quartz (see Polarization of Light). Cinnabar has higher refractive power than any other known mineral, its mean index for sodium light being 3.02, whilst the index for diamond—a substance of remarkable refraction—is only 2.42 (see Refraction). The hardness of cinnabar is 3, and its specific gravity 8.998.
Cinnabar is found in all localities which yield quicksilver, notably Almaden (Spain), New Almaden (California), Idria (Austria), Landsberg, near Ober-Moschel in the Palatinate, Ripa, at the foot of the Apuan Alps (Tuscany), the mountain Avala (Servia), Huancavelica (Peru), and the province of Kweichow in China, whence very fine crystals have been obtained. Cinnabar is in course of deposition at the present day from the hot waters of Sulphur Bank, in California, and Steamboat Springs, Nevada.
Hepatic cinnabar is an impure variety from Idria in Carniola, in which the cinnabar is mixed with bituminous and earthy matter.
Metacinnabarite is a cubic form of mercuric sulphide, this compound being dimorphous.
For a general description of cinnabar, see G. F. Becker’s Geology of the Quicksilver Deposits of the Pacific Slope, U.S. Geol. Surv. Monographs, No. xiii. (1888). (F. W. R.*)