Arsenic sulfide Realgar Orpiment

Arsenic is a metallic element (symbol As atomic no. 33), which exists in several allotropic forms. Various ores contain crystalline forms of arsenic salts cobaltite contains cobalt arsenic sulfide mispickel (arsenopyrite) iron arsenic sulfide orpiment arsenic trisulfide proustite (ruby silver ore) silver arsenic sulfide realgar arsenic sulfide and tennantite copper arsenic sulfide. 

Dimorphite (or dimorphine ) is a soft, yeUow-orange orthorhombic arsenic sulfide mineral. It has chemical composition AS4S3 and forms by deposition from volcanic hot gas vents (Hey, 1993). Whitfield (1970) has reported the synthesis of two crystalline forms (Type 1 and Type 11). Dimorphite is found in volcanic areas such as Attica, Greece and Vesuvius, Italy, where it can occur in association with the arsenic sulfide minerals, orpiment and realgar it is also closely related to other arsenic sulfide minerals duransite and alacranite (qq.v.). 

Arsenic group Arsenic sulfides group Orpiment Realgar Sphalerite FitzHugh (1997) Johan et al. (1973) Marquez-Zavalia et al. (1999) Noll (1981)... 

Arsenic is the 53rd most abundant element and is widely distributed in the Earths crust. It occurs naturally in several minerals, but high-grade deposits are rare. Most of the minerals and ores that contain arsenic also contain other metals. Some major sources of arsenic are the minerals orpiment, scherbenkobalt, arsenopyrite, niccohte, realgar, gersdorffite, and smaltite. In addition, most sulfide ores of other metals also contain some arsenic. The three major minerals that produce arsenic are realgar (arsenic monosulfide, AsS), orpiment (arsenic trisidfide, ASjSj), and arsenopyrite (iron arsenosulfide, FeAsS). 

Synonyms arsenic disulfide arsenic monosulfide red arsenic sulfide ruby arsenic realgar red orpiment. 

Arsenic is found primarily as sulfides in orpiment, As2S3, realgar, AS4S4, and arsenopyrite, FeAsS, but it also occurs as arsenolite, As406. Arsenic compounds have been known since antiquity, and orpiment, which is yellow, was probably used as a yellow pigment. 

Eary (1992) prepared an amorphous sample of AS2S3 by precipitation of the sulfide from an aqueous solution of NaAs02, buffered at pH 4.0, to which was added an excess of Na2S-9H20. The precipitate was aged 1 to 3 days, and washed with water to remove the buffer. X-ray analysis showed no realgar, orpiment, crystalline sulfur or crystalline arsenic. Eary determined the solubility of this material at 298.15 K, 313.15 K, 333.15 K, and 363.15 K in solutions with the presence and absence of added sulfide. He gave equilibrium constants for the reaction ... 

The alkaline earth group as a whole stands in marked contrast to transition metals and post-transition metals. For example, most of the metals in the periodic table form insoluble precipitates with the sulfide ion (S2), with the result that sulfide ores of transition and post-transition metals are very common in Earths crust. Common examples of metal sulfides include galena (lead sulfide), cinnabar (mercury sulfide), gree-nockite (cadmium sulfide), acanthite (silver sulfide), cobaltite (cobalt arsenic sulfide), sphalerite (ZnS), stibnite (antimony sulfide), several copper sulfides, orpiment and realgar (both forms of arsenic sulfide), and pyrite (iron sulfide). None of the alkaline earths, however, are found as sulfides. 

Arsenic sulfides group Alacranite Arsenic sulfide, orpiment type Arsenolite Dimorphite Duranusite Orpiment Pararealgar Realgar Uzonite... 

Arsenic group Arsenic sulfides group Alacranite Duranusite Orpiment Realgar... 

Arsenic group Arsenic sulfides group Alacranite Arsenolite Cinnabar Claudetite Dimorphite Duranusite Orpiment Pararealgar Pyrite Realgar Stibnite Sullur FitzHugh (1997) Migdisov Bychkov (1998)... 

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