Orpiment


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Related to Orpiment: arsenic, cinnabar

orpiment

[′ȯr·pə·mənt]
(mineralogy)
As2S3 A lemon-yellow mineral, crystallizing in the monoclinic system, and generally occurring in foliated or columnar masses; luster is resinous and pearly on the cleavage surface, hardness is 1.5-2 on Mohs scale, and specific gravity is 3.49. Also known as yellow arsenic.

Orpiment

 

arsenic trisulfide, AS2S3. Orpiment contains 60.91 percent arsenic and 39.09 percent sulfur. It has a monoclinic system. The crystals are prismatic; rodlike and columnar aggregates, as well as powdery, nodular, and clustered bodies, are characteristic. Orpiment is easily cut with a knife. Its color ranges from golden- and lemon-yellow to orange-yellow, sometimes brownish. Its luster is oily to diamondlike; on the cleavage planes it is like mother-of-pearl, semimetallic, and tarnishes rapidly. Its hardness on the mineralogical scale is 1.5–2. Its density is 3,490 kg per cu m. It is soluble in aqua regia and bases. It is a nonconductor and diamagnetic. During heating it becomes red. Orpiment is found in low-temperature, hydrothermic deposits in association with realgar, antimony, and other substances, as well as in deposits of hot mineral springs and in volcanic encrustations. It is the raw material from which arsenic compounds are obtained.

A. B. PAVLOVSKII

orpiment

An arsenic sulfur compound; used in paints as a yellow pigment.
References in periodicals archive ?
He mentions orpiment [TEXT NOT REPRODUCIBLE IN ASCII] as occuring in the same mines in Pontus and Cappadocia, different types of clay [TEXT NOT REPRODUCIBLE IN ASCII]--this word was used exclusively for "red ochre" by previous authors).
Some of them are covered by tiny seligmannite crystals, yellow orpiment and powdery orange pararealgar.
Gold is associated with weak to moderate silicification, minor disseminated pyrite and minor amounts of orpiment in well fractured sediments of the Upper Plate Vinini Formation.
Beekman (1992) divides the subject matter covered in the third book as follows: seven chapters on metals, including gold, silver and iron; 13 chapters on minerals, including realgar, orpiment, alum, pyrite, marcasite, gypsum, quartz, alabaster and asbestos; seven chapters on gemstones, including diamonds, rubies, emeralds, sapphires, chrysoberyl, opal and agates; a remarkable 29 chapers on the unremarkable subject of concretions; and a miscellany of chapters on "curiosities," including stones with unusual shapes, porcelain, salt, amber, glass, etc.
A few scattered rhodochrosites were also on hand, but otherwise it was the same mix of nice Chinese minerals and poor Chinese minerals that we've seen for the last several years: fluorite, stibnite, orpiment, quartz, calcite, broken bournonite, etc.
Bright yellow crusts of orpiment partially cover some of the crystal groups, and sharp orpiment epimorphs after realgar crystals to 2.
Non-metallic associations include orpiment and, as gangue minerals, quartz, calcite, gypsum, barite and fluorite; native sulfur is a very late-formed member of the suite.
The Shimen realgar mine, which has been in more or less continuous operation for nearly 1500 years, has yielded world-class specimens of realgar and orpiment, associated with fine calcite crystals, at least since 1988 and as recently as 2006.
Orange-yellow orpiment coating quartz was described by Gordon (1944).
About 15 years ago, the world began to awaken to China's mineral potential as stunning specimens of realgar and orpiment, clusters of azurite and huge stibnite crystals up to 1 meter long arrived at international mineral shows.
When the first new mineral specimens from China began appearing on the mineral Western market in the late 1980's and early 1990's, enormous stibnite crystals, fine cinnabar crystals and fascinating specimens of realgar and orpiment were among the highlights which provided a new impulse to collecting activities.
The characteristic minerals of the mercury deposits include cinnabar, dolomite, quartz, calcite, pyrite, sphalerite, metacinnabar, barite, realgar, orpiment, stibnite and "asphalt.