Realgar

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Template:Short description Template:Infobox mineral

Realgar (Template:IPAc-en Template:Respell), also known as arsenic blende, ruby sulphur or ruby of arsenic, is an arsenic sulfide mineral with the chemical formula Template:Chem2. It is a soft, mineral occurring in monoclinic crystals, or in granular, compact, or powdery form, often in association with the related mineral, orpiment (Template:Chem2). It is orange-red in color, and burns with a bluish flame releasing fumes of arsenic and sulfur. It is trimorphous with pararealgar and bonazziite.<ref name=Handbook/>

Etymology

Its name comes from the Arabic rahj al-ġār (Template:Lang Template:IPA Template:Pronunciation, "powder of the mine"), via Medieval Latin, and its earliest record in English is in the 1390s.<ref name="Websters-Third">Template:Cite book</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref>

Uses

Realgar is a minor ore of arsenic extracted in China, Peru, and the Philippines.<ref>Template:Cite web</ref>

Historical uses

Realgar was used by firework manufacturers in white flame and star compositions and to produce yellow smoke in daytime fireworks.<ref>Template:Cite book</ref><ref>Template:Cite book</ref>

Realgar has been used to kill weeds, insects, and rodents,<ref>Template:Cite report</ref> even though more effective arsenic-based anti-pest agents are available such as cacodylic acid, Template:Chem2, an organoarsenic compound used as an herbicide.Template:Cn

Realgar was also used by Ancient Greek apothecaries to make a medicine known as "bull's blood".<ref name=Arnould>Template:Cite journal</ref> The Greek physician Nicander described a death by "bull's blood", which matches the known effects of arsenic poisoning.<ref name=Arnould/> Bull's blood is the poison that is said to have been used by Themistocles and Midas for suicide.<ref name=Arnould/>

The Chinese name for realgar is Template:Lang (Mandarin Template:Transliteration), literally 'masculine yellow', as opposed to orpiment which is 'feminine yellow'.<ref>Template:Cite journal</ref>

Realgar was, along with orpiment, traded in the Roman Empire and was used as a red paint pigment. Early occurrences of realgar as a red paint pigment are known for works of art from China, India, Central Asia, and Egypt. It was used in Venetian fine-art painting during the Renaissance era, though rarely elsewhere in Europe, a use which died out by the 18th century.<ref>Template:Cite web</ref> It was also used as medicine. Other traditional uses include manufacturing lead shot, printing, and dyeingTemplate:How? calico cloth. It was used to poison rats in medieval Spain and in 16th century England.<ref>Template:Cite book</ref>

Occurrence

Realgar most commonly occurs as a low-temperature hydrothermal vein mineral associated with other arsenic and antimony minerals. It also occurs as volcanic sublimations and in hot spring deposits. It occurs in association with orpiment, arsenolite, calcite and barite.<ref name=Handbook/>

It is found with lead, silver and gold ores in Hungary, Bohemia and Saxony. In the US it occurs notably in Mercur, Utah; Manhattan, Nevada; and in the geyser deposits of Yellowstone National Park.<ref name=Klein/>

After a long period of exposure to light, realgar changes form to a yellow powder known as pararealgar (Template:Chem2). It was once thought that this powder was the yellow sulfide (orpiment), but is a distinct chemical compound.<ref name=AM77>Template:Cite journal</ref>

See also

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References

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Further reading

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