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Realgar ( ), also known as "ruby sulphur" or "ruby of arsenic", is an
arsenic Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, b ...
sulfide mineral with the
chemical formula In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, ...
α-. It is a soft,
sectile Sectility is the ability of a mineral to be cut into thin pieces with a knife. Minerals that are not sectile will be broken into rougher pieces when cut. Metals and paper are sectile. Sectility can be used to distinguish minerals of similar appea ...
mineral occurring in
monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic ...
crystals, or in granular, compact, or powdery form, often in association with the related mineral,
orpiment Orpiment is a deep-colored, orange-yellow arsenic sulfide mineral with formula . It is found in volcanic fumaroles, low-temperature hydrothermal veins, and hot springs and is formed both by sublimation and as a byproduct of the decay of anothe ...
(). It is orange-red in color, melts at 320 °C, and burns with a bluish flame releasing fumes of arsenic and sulfur. Realgar is soft with a
Mohs hardness The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by ...
of 1.5 to 2 and has a
specific gravity Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water at its dens ...
of 3.5. Its streak is orange colored. It is trimorphous with pararealgar and bonazziite. Its name comes from the Arabic ''rahj al-ġār'' (, "powder of the mine"), via
Medieval Latin Medieval Latin was the form of Literary Latin used in Roman Catholic Western Europe during the Middle Ages. In this region it served as the primary written language, though local languages were also written to varying degrees. Latin functioned ...
, and its earliest record in English is in the 1390s.


Uses

Realgar is a minor ore of arsenic extracted in China, Peru, and the Philippines.


Historical uses

Realgar was used by firework manufacturers to create the color white in fireworks prior to the availability of powdered metals such as
aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...
,
magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ...
and
titanium Titanium is a chemical element with the symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion i ...
. It is still used in combination with
potassium chlorate Potassium chlorate is a compound containing potassium, chlorine and oxygen, with the molecular formula KClO3. In its pure form, it is a white crystalline substance. After sodium chlorate, it is the second most common chlorate in industrial use. ...
to make a contact explosive known as "red explosive" for some types of torpedoes and other novelty exploding fireworks branded as 'cracker balls', as well in the cores of some types of crackling stars. Realgar is toxic. It was sometimes used to kill weeds,
insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...
s, and
rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are n ...
s, even though more effective arsenic-based anti-pest agents are available such as cacodylic acid, , an
organoarsenic compound Organoarsenic chemistry is the chemistry of compounds containing a chemical bond between arsenic and carbon. A few organoarsenic compounds, also called "organoarsenicals," are produced industrially with uses as insecticides, herbicides, and fun ...
used as
herbicide Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page f ...
and also to kill ants and
mice A mouse ( : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus'' ...
. Realgar was commonly used in leather manufacturing to remove hair from animal pelts. Because it is a known
carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive sub ...
and an arsenic poison, and because substitutes are available, it is rarely used today for this purpose. The ancient Greeks, who called realgar (), understood that it was poisonous. From this, realgar has also historically been known in English as ''sandarac''. Realgar was also used by Ancient Greek apothecaries to make a medicine known as "bull's blood". The Greek physician
Nicander Nicander of Colophon ( grc-gre, Νίκανδρος ὁ Κολοφώνιος, Níkandros ho Kolophṓnios; fl. 2nd century BC), Greek poet, physician and grammarian, was born at Claros (Ahmetbeyli in modern Turkey), near Colophon, where his fam ...
described a death by "bull's blood", which matches the known effects of arsenic poisoning. Bull's blood is the poison that is said to have been used by
Themistocles Themistocles (; grc-gre, Θεμιστοκλῆς; c. 524–459 BC) was an Athenian politician and general. He was one of a new breed of non-aristocratic politicians who rose to prominence in the early years of the Athenian democracy. As ...
and Midas for suicide. The Chinese name for realgar is ( Mandarin ), literally 'masculine yellow', as opposed to
orpiment Orpiment is a deep-colored, orange-yellow arsenic sulfide mineral with formula . It is found in volcanic fumaroles, low-temperature hydrothermal veins, and hot springs and is formed both by sublimation and as a byproduct of the decay of anothe ...
which is 'feminine yellow'. Realgar was, along with
orpiment Orpiment is a deep-colored, orange-yellow arsenic sulfide mineral with formula . It is found in volcanic fumaroles, low-temperature hydrothermal veins, and hot springs and is formed both by sublimation and as a byproduct of the decay of anothe ...
, traded in the
Roman Empire The Roman Empire ( la, Imperium Romanum ; grc-gre, Βασιλεία τῶν Ῥωμαίων, Basileía tôn Rhōmaíōn) was the post-Roman Republic, Republican period of ancient Rome. As a polity, it included large territorial holdings aro ...
and was used as a red paint
pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compou ...
. Early occurrences of realgar as a red paint pigment are known for works of art from
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
,
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
,
Central Asia Central Asia, also known as Middle Asia, is a region of Asia that stretches from the Caspian Sea in the west to western China and Mongolia in the east, and from Afghanistan and Iran in the south to Russia in the north. It includes the fo ...
, and
Egypt Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a List of transcontinental countries, transcontinental country spanning the North Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via a land bridg ...
. It was used in European fine-art painting during the
Renaissance The Renaissance ( , ) , from , with the same meanings. is a period in European history marking the transition from the Middle Ages to modernity and covering the 15th and 16th centuries, characterized by an effort to revive and surpass ide ...
era, a use which died out by the 18th century. It was also used as medicine. Other traditional uses include manufacturing lead shot, printing, and dyeing calico cloth. It was used to poison rats in medieval Spain and in 16th century England.


Occurrence

Realgar most commonly occurs as a low-temperature hydrothermal
vein Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated ...
mineral associated with other arsenic and antimony minerals. It also occurs as volcanic sublimations and in
hot spring A hot spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow bodies of magma (molten rock) or by circ ...
deposits. It occurs in association with
orpiment Orpiment is a deep-colored, orange-yellow arsenic sulfide mineral with formula . It is found in volcanic fumaroles, low-temperature hydrothermal veins, and hot springs and is formed both by sublimation and as a byproduct of the decay of anothe ...
, arsenolite,
calcite Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scratc ...
and
barite Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate ( Ba S O4). Baryte is generally white or colorless, and is the main source of the element barium. The ''baryte group'' consists of baryte, celestine (strontium sulfate), ...
. It is found with
lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, ...
,
silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...
and
gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...
ores Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 April ...
in
Hungary Hungary ( hu, Magyarország ) is a landlocked country in Central Europe. Spanning of the Carpathian Basin, it is bordered by Slovakia to the north, Ukraine to the northeast, Romania to the east and southeast, Serbia to the south, Cr ...
,
Bohemia Bohemia ( ; cs, Čechy ; ; hsb, Čěska; szl, Czechy) is the westernmost and largest historical region of the Czech Republic. Bohemia can also refer to a wider area consisting of the historical Lands of the Bohemian Crown ruled by the Bohem ...
and
Saxony Saxony (german: Sachsen ; Upper Saxon German, Upper Saxon: ''Saggsn''; hsb, Sakska), officially the Free State of Saxony (german: Freistaat Sachsen, links=no ; Upper Saxon: ''Freischdaad Saggsn''; hsb, Swobodny stat Sakska, links=no), is a ...
. In the US it occurs notably in Mercur, Utah;
Manhattan, Nevada Manhattan is an unincorporated town in Nye County, Nevada, located at the end of Nevada State Route 377, about north of Tonopah, the county seat. History It originally was founded in 1867 as part of the silver mining boom. George Wheeler fo ...
; and in the
geyser A geyser (, ) is a spring characterized by an intermittent discharge of water ejected turbulently and accompanied by steam. As a fairly rare phenomenon, the formation of geysers is due to particular hydrogeological conditions that exist only i ...
deposits of
Yellowstone National Park Yellowstone National Park is an American national park located in the western United States, largely in the northwest corner of Wyoming and extending into Montana and Idaho. It was established by the 42nd U.S. Congress with the Yellowst ...
. After a long period of exposure to
light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 t ...
, realgar changes form to a
yellow Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In th ...
powder known as pararealgar (β-). It was once thought that this powder was the yellow sulfide
orpiment Orpiment is a deep-colored, orange-yellow arsenic sulfide mineral with formula . It is found in volcanic fumaroles, low-temperature hydrothermal veins, and hot springs and is formed both by sublimation and as a byproduct of the decay of anothe ...
, but is a distinct chemical compound.


Gallery

Image:Realgar-unit-cell-3D-balls.png, The unit cell of realgar, showing clearly the molecules it contains File:Realgar-md56a.jpg, Cluster of realgar crystals from Getchell Mine, Adam Peak, Potosi District, Humboldt County, Nevada, United States File:Realgar-Picropharmacolite-117490.jpg, Cherry-red realgar crystals atop a matrix, and a sharp acicular spray of the rare species picropharmacolite (white needles) below File:Réalgar, quartz, chalcopyrite, galène 90.3.9834.jpg, Crystals of realgar, quartz, chalcopyrite and galena, from Quiruvilca Mine, La Libertad, Peru


See also

*
Classification of minerals The classification of minerals is a process of determining to which of several groups minerals belong based on their chemical characteristics. Since the 1950s, this classification has been carried out by the International Mineralogical Association, ...
*
List of inorganic pigments The following list includes commercially or artistically important inorganic pigments of natural and synthetic origin.. Purple pigments Aluminum pigments * Ultramarine violet: (PV15) - a synthetic or naturally occurring sulfur containing silic ...
*
List of minerals This is a list of minerals for which there are articles on Wikipedia. Minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish the various ''species''. Within a m ...


References


Further reading

* ''The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals''. 11th Edition. Ed. Susan Budavari. Merck & Co., Inc., N.J., U.S.A. 1989. * William Mesny. ''Mesny’s Chinese Miscellany. A Text Book of Notes on China and the Chinese.'' Shanghai. Vol. III, (1899), p. 251; Vol. IV, (1905), pp. 425–426. * American Mineralogist Vol 80, pp 400–403, 199

* American Mineralogist Vol 20, pp 1266–1274, 199


External links


Mindat.org: Pararealgar
{{Sulfur compounds Arsenic minerals Sulfide minerals Alchemical substances Monoclinic minerals Minerals in space group 14 Inorganic pigments