| Cinnabar | |
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Cinnabar on Dolomite |
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| General | |
| Category | Sulfide mineral |
| Chemical formula | mercury(II) sulfide, HgS |
| Strunz classification | 02.CD.15a |
| Crystal symmetry | Trigonal Trapezohedral H-M symbol: 3 2 Space group: P31 2 1 |
| Unit cell | a = 4.145(2) Å, c = 9.496(2) Å, Z=3 |
| Identification | |
| Color | Cochineal-red, towards brownish red and lead-gray |
| Crystal habit | Rhombohedral to tabular; granular to massive and as incrustations |
| Crystal system | Trigonal |
| Twinning | Simple contact twins, twin plane {0001} |
| Cleavage | Prismatic {1010}, perfect |
| Fracture | Uneven to subconchoidal |
| Tenacity | Slightly sectile |
| Mohs scale hardness | 2-2.5 |
| Luster | Adamantine to dull |
| Streak | Scarlet |
| Diaphaneity | Transparent in thin pieces |
| 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 (pronounced /ˈsɪnəbɑr/) or cinnabarite (/sɪnəˈbɑraɪt/) (red mercury(II) sulfide (HgS), native vermilion), is the common ore of mercury.
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The name comes from κινναβαρι (kinnabari), a Greek word most likely applied by Theophrastus to several distinct substances. Other sources say the word comes from the Persian شنگرف shangarf (زینجیفرح zinjifrah), a word of uncertain origin (also compare, Sanskrit: sugara). In Latin it was sometimes known as minium, meaning also "red lead", though both of these terms now refer specifically to lead tetroxide.
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 zincblende structure.
Cinnabar is generally found in a massive, granular or earthy form and is bright scarlet to brick-red in color.[6] It occasionally occurs 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 is 2.42 and that for gallium (III) arsenide (GaAs) is 3.93.
Generally cinnabar occurs as a vein-filling mineral associated with recent volcanic activity and alkaline hot springs. Cinnabar is deposited by epithermal ascending aqueous solutions (those near surface and not too hot) far removed from their igneous source.
It is associated with native mercury, stibnite, realgar, pyrite, marcasite, opal, quartz, chalcedony, dolomite, calcite and barite.[2]
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 and in the Mount Amiata (Tuscany); the mountain Avala (Serbia); Huancavelica (Peru); Murfreesboro, Arkansas; Terlingua (Texas); and the province of Guizhou in China, where fine crystals have been obtained. It was also mined near Red Devil, Alaska on the middle Kuskokwim River. Red Devil was named after the Red Devil cinnabar mine, a primary source of mercury.
Cinnabar is still being deposited at the present day from the hot waters of Sulphur Bank Mine in California and Steamboat Springs, Nevada.
Cinnabar has been mined since the Neolithic Age.[9] During the Roman Empire it was mined 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.
Because of its mercury content, cinnabar can be toxic to human beings. Though ancient peoples in South America often used cinnabar for art, or processed it into refined mercury (as a means to gild silver and gold to objects) "the toxic properties of mercury were well known. It was dangerous to those who mined and processed cinnabar, it caused shaking, loss of sense, and death...data suggest that mercury was retorted from cinnabar and the workers were exposed to the toxic mercury fumes."[10] Overexposure to mercury, mercurialism, was seen as an occupational disease to the ancient Romans, "Mining in the Spanish cinnabar mines of Almaden, 225 km southwest of Madrid, was regarded as being akin to a death sentence due to the shortened life expectancy of the miners, who were slaves or convicts."[11]
Cinnabar turned into a fine powder is often referred to as vermilion which can be used as a food coloring in extremely small amounts. Animal testing has shown vermilion "proved fatal to animals in the proportion of from thirty to seventy grains, even when applied externally to a wound."[12]
Cinnabar has been used for its color in the new world since the Olmec culture.[13] Cinnabar was often used in royal burial chambers during the peak of Mayan civilization.[14]
The most popularly known use of cinnabar is in Chinese carved lacquerware, a technique that apparently originated in the Song Dynasty. The danger of mercury poisoning may be reduced in ancient lacquerware by entraining the powdered pigment in lacquer,[15] 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.
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