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- For the moth, see Cinnabar moth.
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Structure
HgS adopts two structures, i.e. it is dimorphous.Wells, A.F. (1984). Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6. The more stable form is cinnabar, which has a structure akin to that for HgO: each Hg center has two short Hg-S bonds (2.36 Å), and four longer Hg---S contacts (3.10, 3.10, 3.30, 3.30 Å). The black form of HgS has the zinc blende structure.
Properties
Cinnabar is generally found in a massive, granular or earthy form and is bright scarlet to brick-red in color. It occasionally occurs, however, in crystals with a metallic adamantine luster. The crystals belong to the rhombohedral (trigonal) system, and are generally of rhombohedral habit, sometimes twinned. The twinning in cinnabar is distinctive and forms a penetration twin that is ridged with six ridges surrounding the point of a pyramid. It could be thought of as two scalahedral crystals grown together with one crystal going the opposite way of the other crystal. The hardness of cinnabar is 2 - 2.5, and its specific gravity 8.998.
Cinnabar resembles quartz in its symmetry and certain of its optical characteristics. Like quartz, it exhibits birefringence. It has the highest refractive power of any mineral. Its mean index for sodium light is 3.02, whereas the index for diamond—a substance of remarkable refraction— is 2.42 and that for GaAs is 3.93. See List of indices of refraction.
Occurrence
Cinnabar was mined by the Roman Empire for its mercury content, and it has been the main ore of mercury throughout the centuries. Some mines used by the Romans remain active today. Generally cinnabar occurs as a vein-filling mineral associated with recent volcanic activity and alkaline hot springs.
Cinnabar is found in all localities that yield mercury, notably Almaden (Spain), New Almaden (California), Idrija (Slovenia), New Idria (California), Landsberg, near Ober-Moschel in the Palatinate, Ripa, at the foot of the Apuan Alps (Tuscany), the mountain Avala (Serbia), Huancavelica (Peru), Terlingua (Texas), and the province of Guizhou in China, where fine crystals have been obtained. Cinnabar is still being deposited at the present day from the hot waters of Sulphur Bank, in California, and Steamboat Springs, Nevada.
Extraction of mercury from ore
To produce liquid (quicksilver) mercury, crushed cinnabar ore is roasted in rotary furnaces. Pure mercury separates from sulfur in this process and easily evaporates. A condensing column is used to collect the liquid mercury, which is most often shipped in iron flasks. Abandoned mercury mine processing sites often contain very hazardous waste piles of roasted cinnabar calcines.
Other forms of cinnabar
- Hepatic cinnabar is an impure variety from Idrija in Carniola, in which the cinnabar is mixed with bituminous and earthy matter.
- Metacinnabarite is a black-colored form of HgS, which crystallizes in the cubic form.
- Synthetic cinnabar is produced by treatment of Hg(II) salts with hydrogen sulfide to precipitate black, synthetic metacinnabarite, which is then heated in water. This conversion is promoted by the presence of sodium sulfide.Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
References
External links
See also
Sulfide minerals | Mercury minerals
Zinnober | Kinaver | Cinabrio | Cinabre | Cinabrio | Cinabro | צינובר | Cinobrs | Cinoberis (mineralas) | Cinnaber | 辰砂 | Cynober | Cinábrio | Киноварь | Rumelka | Sinooperi | 朱砂
"Cinnabar"