Realgar


Also found in: Dictionary, Thesaurus, Medical, Wikipedia.
Related to Realgar: arsenopyrite

realgar

[rē′al‚gär]
(mineralogy)
AsS A red to orange mineral crystallizing in the monoclinic system, having a resinous luster and found in short, vertical striated crystals; specific gravity is 3.48, and hardness is 1.5-2 on Mohs scale. Also known as red arsenic; red orpiment; sandarac.

Realgar

 

a mineral, arsenic monosulfide (AsS); contains 70.1 percent arsenic.

Realgar has a complex crystal structure. The lattice is constructed of individual As4S4 molecules, with the sulfur ions forming a square, and the arsenic ions a tetrahedron; the centers of the square and tetrahedron coincide. Realgar crystallizes in the monoclinic system, forming bright orange-red prismatic crystals. It occurs most commonly in the form of compact granular masses or powdery, earthy aggregates. The mineral has a density of 3,560–3,590 kg/m3 and is sectile; its hardness is 1.5–2 on Mohs’ scale.

Realgar is usually found together with orpiment, stibnite, and lead, silver, and gold ores of hydrothermal origin but may also occur as a sublimation product of volcanic eruptions or as a deposit from hot springs. When exposed to sunlight, it decomposes into orange to lemon-yellow orpiment, As2S3. Realgar is an important ore for the extraction of arsenic. In the USSR, deposits of realgar are found in Transcaucasia; there are also major deposits in such countries as Czechoslovakia, Rumania, Greece, the USA, and Japan.

References in periodicals archive ?
He also mentions the fact that clay (argilla) is used for iron welding, and further orpiment (auripigmentum), realgar (sandaraca), minium (minium) from silver-mines (used as a pigment), ruddle or red ochre (rubrica, Greek miltos), cinnabar (cinnabaris) and Sinopian earth (sinopis) for painting, yellow ochre (sil) from gold- and silver-mines ("the best [.
For instance, the combination of Realgar (tetraarsenic tetrasulfide), Indigo Naturalis, Radix Salviae Miltiorrhizae and Radix Pseudostellariae has been proved to be effective in the treatment of human acute promyelocytic leukemia (APL).
Realgar with Calcite Jiepaiyu Mine, Shimen, Hunan Prov.
The program met its objectives, successfully filling in the gaps in the resource model, extending and defining the near surface limits of previously known mineralization (as shown on the attached map) and resulting in the discovery of a new zone of mineralization, the Realgar Zone, at the intersection of the Black and Central Zones.
You will recall that in late 2005 and into 2006 the market was briefly flush with superb specimens of realgar from a then-new find in one of the old mines of Baia Sprie (formerly Felsobnsanya), Romania.
Within the intrusive and intrusive breccia, oxidation is less well developed and primary sulphides and realgar are observed in a number of drill holes.
For instance, it is reported that the combination of Realgar (tetraarsenic tetrasulfide), Indigo Naturalis, Radix Salviae Miltiorrhizae and Radix Pseudostellariae had exerted a synergic effect in treating human acute promyelocyte leukemia (APL) (Wang et al.
These include: (1) chemically reactive sedimentary carbonate rocks; (2) range front faults with accompanying heavy rock brecciation; (3) frontal fault jasperoids with stibnite and fluorite and high contents of arsenic, antimony and mercury; (4) overall hydrothermal mineral assemblage of stibnite, realgar, cinnabar, fluorite, and barite; and (5) widespread presence of anomalous amounts of gold.
Realgar specimens are infamous for their photosensitivity, cracking apart and changing from a beautiful dark red color to orange and yellow if they are not kept strictly in the dark.
Jaroslav Hyrsl's article in March-April 2008 brought the small, inactive Palomo mine, in Huancavelica Department, to our attention, chiefly noting the very nice realgar specimens found there in 2006.
Oh yes, Jaroslav also offered thumbnails showing blocky, bright red realgar crystals to 1.
Since 2000 the Palomo mine has sparingly produced excellent and distinctive specimens of realgar--the author of this article brought a fine lot of realgar specimens to the 2007 Tucson Show.