- For the moth, see Cinnabar moth.
Cinnabar, sometimes written cinnabarite, is a name applied to red mercury(II) sulfide (HgS), or native vermilion, the common ore of mercury. The name comes from the Greek - "kinnabari" - used by Theophrastus, and was probably
applied to several distinct substances. Other sources say the word comes from the Persian zinjifrah, a word of uncertain origin. In Latin it was known as minium, meaning
also "red lead" - a word borrowed from Iberian (cf. Basque armineá "cinnabar").
Structure
HgS adopts two structures, i.e. it is dimorphous.[1] 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 non-metallic adamantine luster. Cinnabar has a rombohedral bravais lattice, and belongs to
the hexagonal crystal system, trigonal division. Its crystals grow usually in a massive habit, though they are 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.
Cinnabar Mercury ore from Nevada, USA
Occurrence
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 Almadén (Spain); New Almaden (California); Hastings Mine and St. Johns Mine, Vallejo, California;[2] Idrija (Slovenia); New Idria (California); Landsberg, near Obermoschel 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.
Cinnabar crystals on Dolomite from China.
Mining and extraction of mercury
Cinnabar was mined by the Roman Empire both as a pigment (Vitruvius, DA VII; IV-V)
(Pliny, HN; XXXIII, XXXVI-XLII) and for its mercury content (Pliny HN; XXXIII, XLI), and it has been the main source of mercury
throughout the centuries. Some mines used by the Romans remain active today. [citation needed]
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.
Because of the high toxicity of mercury, both the mining of cinnabar and refining for mercury are hazardous and historic
causes of mercury poisoning. In particular, the Romans used convict labor in their
mines as a form of death sentence. The Spanish also used shorter term convict labor at the Almadén mines, with a 24% overall fatality rate in one 30 year period.
Abandoned mercury mine processing sites often contain very hazardous waste piles of roasted cinnabar calcines. Water runoff
from such sites is a recognized source of ecological damage.
Cinnabar was often used in royal burial chambers during the peak of Mayan civilization. The red stone was inserted into
limestone sarcophagi, both as a decoration and, more importantly, to deter vandals and thieves with its well-known
toxicity.[citation needed]
Medicinal use
Although cinnabar is known to be highly toxic,[1] it is nevertheless
used (as is arsenic), in powdered form mixed with water, in traditional Chinese medicine (TCM). Although cinnabar is not used in Western medicine, TCM
practitioners sometimes prescribe it as part of a medicinal mixture, often on the basis of the concept of "using poison to cure
poison." Used internally, cinnabar is believed to clear away "heat" and tranquilize the mind. It is also used as a tonic to
reduce the incidence of heart palpitations, restlessness, and insomnia, and to treat sore throats and cold sores that occur in
the mouth and tongue. In addition, cinnabar is applied externally to treat certain skin disorders and infections.[2]
Other forms of cinnabar
- Hepatic cinnabar is an impure variety from the mines of Idrija in the Carniola region of Slovenia, 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.[3]
- Hypercinnabar, crystallise in the hexagonal form.
References
- ^ Wells, A.F. (1984). Structural Inorganic Chemistry, Oxford: Clarendon
Press. ISBN 0-19-855370-6.
- ^ C.Michael Hogan, Marc Papineau et al., Environmental Assessment of the columbus Parkway Widening between Ascot Parkway and the Northgate
Development, Vallejo, Earth Metrics Inc. Report 7853, California State Clearinghouse, Sept, 1989
- ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San
Diego, 2001. ISBN 0-12-352651-5.
External links
See also
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