cinnabar

Cinnabar
Cinnabar on Dolomite
General
Category	Mineral
Chemical formula	mercury(II) sulfide, HgS
Identification
Color	Brownish-red
Crystal habit	Rhombohedral to tabular. Granular to massive
Crystal system	Trigonal - Trapezohedral
Cleavage	Prismatic, perfect
Fracture	Uneven to subconchoidal
Mohs scale hardness	2-2.5
Luster	Adamantine to dull
Streak	Scarlet
Specific gravity	8.176
Optical properties	Uniaxial (+)
Refractive index	nω = 2.905 nε = 3.256
Birefringence	δ = 0.351
Solubility	1.04 x 10-25 g per 100 ml water (Ksp at 25°C = 2 x 10-32)[1]
References	[2][3][4]

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 sometimes known as minium, meaning also "red lead", though both of these terms now refer uniquely to lead tetroxide.

Structure

HgS adopts two structures, i.e. it is dimorphous.^[5] 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.^[6] It occasionally occurs, however, in crystals with a non-metallic adamantine luster. Cinnabar has a rhombohedral 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 8.1.

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 3.08,^[7] whereas the index for diamond—a substance of remarkable refraction— is 2.42 and that for gallium (III) arsenide (GaAs) is 3.93.

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 Puerto Princesa (Philippines); Almadén (Spain); New Almaden (California); Hastings Mine and St. John's Mine, Vallejo, California;^[8] Idrija (Slovenia); New Idria (California); Giza,Egypt; Landsberg, near Obermoschel in the Palatinate; Ripa, at the foot of the Apuan Alps (Tuscany); the mountain Avala (Serbia); Laaren, the Netherlands^{[citation needed]}; Huancavelica (Peru); Murfreesboro, Arkansas 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 Mine, in California, and Steamboat Springs, Nevada.

Mining and extraction of mercury

Cinnabar crystals on dolomite from China.

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.

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 metal, which is most often shipped in iron flasks.

Decorative use

Cinnabar has been used for its color in the new world since the Olmec culture.^[9] 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.^[10]

The most popularly known use of cinnabar is in Chinese carved lacquerware, a technique that apparently originated in the Song Dynasty.^[11] The danger of mercury poisoning may be reduced in ancient lacquerware by entraining the powdered pigment in lacquer,^[12] but could still pose an environmental hazard if the pieces were accidentally destroyed. In the modern jewelry industry, the toxic pigment is replaced by a resin-based polymer that approximates the appearance of pigmented lacquer.

In the Byzantine Empire, the Emperor and certain privileged bishops (such as the Ecumenical Patriarch and the Archbishop of Cyprus) were allowed the exclusive right of signing their names with ink colored vermilion by the addition of cinnabar.^{[citation needed]}

Medicinal use

Despite its toxicity, cinnabar has historically been used in traditional Chinese medicine, where it is called zhūshā (朱砂).

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.^[13]
• Hypercinnabar, crystallise in the hexagonal form.

See also

• China red
• List of minerals

References

1. ^ Meyers, J., Chem. Ed. 63: 689, 1986 
2. ^ Mineral Handbook
3. ^ Mindat
4. ^ Webmineral
5. ^ Wells, A.F. (1984). Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.
6. ^ King, R. J.. "Minerals explained 37: Cinnabar". Geology Today 18 (5): 195–199. doi:10.1046/j.0266-6979.2003.00366.x. 
7. ^ Schumann, Walter (1997). Gemstones of the World. New York: Sterling. ISBN 0806994614. 
8. ^ 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
9. ^ New World's Oldest, in Time Magazine, Monday, Jul. 29, 1957
10. ^ Cinnabar-covered ruin.
11. ^ http://www.askasia.org/teachers/images/image.php?no=659
12. ^ http://www.cst.cmich.edu/users/dietr1rv/cinnabar.htm R. V. Dietrich, 2005
13. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.

Other references

• Martín-Gil, J; Martín-Gil, FJ; Delibes-de-Castro, G; Zapatero-Magdaleno, P; Sarabia-Herrero, FJ (1995). The first use of vermillion. Cellular and Molecular Life Sciences, 51(8):759-761

External links

• MSDS for cinnabar
• Dartmouth Toxic Metals Research Program - Mercury
• Cinnabar visual reference