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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
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and as a byproduct of the decay of another arsenic sulfide mineral, realgar. Orpiment takes its name from the Latin ''auripigmentum'' (''aurum'', "gold" + ''pigmentum'', " pigment") because of its deep-yellow color.


Historical uses

Orpiment was traded in the Roman Empire and was used as a medicine in
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
, even though it is very toxic. It has been used as fly poison and to tip arrows with poison. Because of its striking color, it was of interest to alchemists, both in China and the West, searching for a way to make gold. It also has been found in the wall decorations of Tutankhamun's tomb and ancient Egyptian scrolls, and on the walls of the Taj Mahal. For centuries, orpiment was ground down and used as a pigment in painting and for sealing wax, and was even used in ancient China as a
correction fluid A correction fluid is an opaque, usually white fluid applied to paper to mask errors in text. Once dried, it can be handwritten or typed upon. It is typically packaged in small bottles, lids attached to brushes (or triangular pieces of foam) th ...
. It was one of the few clear, bright-yellow pigments available to artists until the 19th century. However, its extreme toxicity and incompatibility with other common pigments, including lead and copper-based substances such as
verdigris Verdigris is the common name for blue-green, copper-based pigments that form a patina on copper, bronze, and brass. The technical literature is ambiguous as to its chemical composition. Some sources refer to "neutral verdigris" as copper(II) ac ...
and azurite, meant that its use as a pigment ended when
cadmium yellow Cadmium pigments are a class of pigments that contain cadmium. Most of the cadmium produced worldwide has been for use in rechargeable nickel–cadmium batteries, which have been replaced by other rechargeable nickel-chemistry cell varieties ...
s, chromium yellows and organic
dye A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution an ...
-based colors were introduced during the 19th century. Orpiment is mentioned in the 17th century by
Robert Hooke Robert Hooke FRS (; 18 July 16353 March 1703) was an English polymath active as a scientist, natural philosopher and architect, who is credited to be one of two scientists to discover microorganisms in 1665 using a compound microscope that ...
in '' Micrographia'' for the manufacture of small
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. Scientists like Richard Adolf Zsigmondy and
Hermann Ambronn Ernst Ludwig Victor Hermann Ambronn (11 August 1856, Meiningen – 28 March 1927, Jena) was a German botanist and microscopist. Ambronn studied at the universities of Heidelberg, Vienna and Berlin, where his instructors were Leopold Kny and Si ...
puzzled jointly over orpiment glass as early as 1904.


Contemporary uses

Orpiment is used in the production of infrared-transmitting glass,
oil cloth Oilcloth, also known as enameled cloth or American cloth, is close-woven cotton duck or linen cloth with a coating of boiled linseed oil to make it waterproof. Manufacture Boiled linseed oil was prepared by a long boiling of linseed oil with me ...
, linoleum, semiconductors, photoconductors, pigments, and fireworks. Mixed with two parts of
slaked lime Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula Ca( OH)2. It is a colorless crystal or white powder and is produced when quicklime (calcium oxide) is mixed or slaked with water. It has ma ...
(calcium hydroxide), orpiment is still commonly used in rural India as a depilatory. It is used in the tanning industry to remove hair from hides.


Physical and optical properties

Orpiment is a common monoclinic arsenic sulfide mineral. It has a Mohs hardness of 1.5 to 2 and a specific gravity of 3.49. It melts at to . Optically, it is biaxial (−) with refractive indices of ''a'' = 2.4, ''b'' = 2.81, ''g'' = 3.02.


Crystal structure

File:Orpiment-unit-cell-3D-balls.png, File:Orpiment-layer-3D-balls.png, File:Orpiment-layers-stacking-3D-balls.png,


Gallery of orpiment specimens

File:Orpiment.ვკ.jpg, Orpiment from
Racha Racha (also Račha, , ''Račʼa'') is a highland area in western Georgia, located in the upper Rioni river valley and hemmed in by the Greater Caucasus mountains. Under Georgia's current subdivision, Racha is included in the Racha-Lechkhumi and ...
, northern Georgia region File:Orpiment-Realgar-Quartz-154641.jpg, Orpiment and realgar on a vuggy, quartz matrix, Nishinomaki Mine, Gunma Prefecture, Japan File:MFN MIN 1977 0028 Auripigment.jpg, Orpiment from La Libertad, Quiruvilca, Peru File:Orpiment-d06-185b.jpg, El'brusskiy arsenic mine, Kabardino-Balkarian Republic, Northern Caucasus Region, Russia


See also

* List of inorganic pigments


References

* ''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. 26. * Fitzhugh, E.W., Orpiment and Realgar, in Artists’ Pigments, A Handbook of Their History and Characteristics, Vol 3: E.W. Fitzhugh (Ed.) Oxford University Press 1997, p. 47 – 80


External links


Webexhibits "Pigments Through the Ages: Orpiment"

Babylonian Talmud Tractate Chullin
see Rashi 'haZarnich'
Orpiment
Colourlex {{Commons category, Orpiment Arsenic minerals Sulfide minerals Inorganic pigments Alchemical substances Monoclinic minerals Minerals in space group 14