Arsenopyrites

Some of the most important metal sulfides are pyrite [1309-36-0] EeS2 chalcopyrite [1308-56-1J, CuEeS2 pyrrhotite [1310-50-5] Ee sphalerite [12169-28-7] ZnS galena [12179-39-4] PbS arsenopyrite [1303-18-0] 2 pentlandite [53809-86-2] (Fe,Ni)2Sg. Sulfide deposits often occur in... 

Metafile arsenic can be obtained by the direct smelting of the minerals arsenopyrite or loeUingite. The arsenic vapor is sublimed when these minerals are heated to about 650—700°C in the absence of air. The metal can also be prepared commercially by the reduction of arsenic trioxide with charcoal. The oxide and charcoal are mixed and placed into a horizontal steel retort jacketed with fire-brick which is then gas-fired. The reduced arsenic vapor is collected in a water-cooled condenser (5). In a process used by Bofiden Aktiebolag (6), the steel retort, heated to 700—800°C in an electric furnace, is equipped with a demountable air-cooled condenser. The off-gases are cleaned in a sembber system. The yield of metallic arsenic from the reduction of arsenic trioxide with carbon and carbon monoxide has been studied (7) and a process has been patented describing the gaseous reduction of arsenic trioxide to metal (8). 

Minor quantities of arsenic trioxide have been obtained from the roasting of arsenopyrite, but the presence of copious amounts of SO2 iu the gas and vapor stream requires the use of lead-lined kitchens (9). 

Arsenic trioxide may be made by burning arsenic in air or by the hydrolysis of an arsenic trihaUde. Commercially, it is obtained by roasting arsenopyrite [1303-18-0] FeAsS. It dissolves in water to a slight extent (1.7 g/100 g water at 25°C) to form a weaMy acidic solution which probably contains the species H AsO, orthoarsenous acid [36465-76-6]. The oxide is amphoteric and hence soluble in acids and bases. It is frequendy used as a primary analytical standard in oxidimetry because it is readily attainable in a high state of purity and is quantitatively oxidized by many reagents commonly used in volumetric analysis, eg, dichromate, nitric acid, hypochlorite, and inon(III). 

Gift-jasmin, m. Carolina jasmine (Gelsemium sempervirens). -kies, m. arsenopyrite. -kobalt, m. native arsenic, -kraut, n. poisonous plant, -kunde, /. toxicology, -lattich, m. strong-scented lettuce (Lactuea virosa). -lehre, /. toxicology. 

Weiss-kies, m. arsenopyrite. -klee, m. white clover. 

An alternative route increasingly investigated is bio-oxidation using bacteria to oxidize pyrite or arsenopyrites at 45°C. 

Huggins (1922) was the first investigator to assign structures to sphalerite, wurtzite, chalcopyrite, pyrite, marcasite, arsenopyrite, and other sulfide minerals in which each sulfur atom forms four tetrahedrally directed covalent bonds with surrounding atoms. These structures would be described as involving quadricovalent argononic S2+. 

Buerger, M. J. (1937) Interatomic distances in marcasite and notes on the bonding in crystals of Iollingite, arsenopyrite, and marcasite types. Z. Kristallogr. A97, 504-513. 

Sanru aguilarite, naumannite, polybasite, pyrargyrite, stephanite electrum, miargyrite, chalcopyrite, fahore, arsenopyrite, marcasite, pyrite, sphalerite, stibnite cinnabar quartz, adularia, kaolinite, sericite, calcite... 

Mutsu krennerite, native tellurium chalcopyrite, fahore, arsenopyrite, marcasite, pyrile quartz... 

Iriki fahore, gold-fieldite, native tellurium fahore, famatinite argentite, chalcopyrite, fabore, famatinite, arsenopyrite, marcasitc, pyrite, pyrrhotite quartz, kaolinite, anatase... 

Main opaque minerals are chalcopyrite, cassiterite, stannite, arsenopyrite, bismuth-inite, pyrrhotite and sphalerite. The FeS content of sphalerite is high (about 18 mol% FeS). 

Opaque minerals include stibnite, jamesonite, cinnabar, gold, pyrite, pyrrhotite, arsenopyrite, marcasite, sphalerite, galena and chalcopyrite. 

The ore minerals display a zonal distribution gold and cinnabar are enriched in the upper part of the veins, and sphalerite, galena and chalcopyrite are more abundant in the deeper parts. Pyrrhotite and arsenopyrite are distributed throughout the veins. 

From the mode of occurrence of opaque minerals it is considered that pyrrhotite and sphalerite were precipitated at an early-stage, gold, pyrite, marcasite, stibnite and cinnabar were precipitated at a late-stage, and arsenopyrite was precipitated throughout the mineralization period. 

Occurrence of pyrrhotite, arsenopyrite and high iron content of sphalerite indicate low fs,2 and /02 conditions. Decrepitation temperatures of fluid inclusions in quartz from Sn-Cu-As stage are 403-322°C (Enjoji and Takenouchi, 1976). 

Main opaque minerals include native gold, electrum, pyrite, pyrrhotite, chalcopy-rite, cubanite, sphalerite, arsenopyrite and tellurobismutite. The amounts of these sulfide minerals are poor, compared with those in epithermal Au-Ag vein-type deposits. It is noteworthy that silver minerals are abundant in epithermal Au-Ag vein-type deposits, whereas they are poor in gold-quartz veins. 

The veins are composed mostly of quartz and a small amount of sulfide minerals (pyrite, pyrrhotite, arsenopyrite, chalcopyrite, sphalerite, and galena), carbonate minerals (calcite, dolomite) and gold, and include breccias of the host rocks with carbonaceous matters. Layering by carbonaceous matters has been occasionally observed in the veins. Banding structure, wall rock alteration and an evidence of boiling of fluids that are commonly observed in epithermal veins have not been usually found. 

The adsorption of collectors on sulfide mineral occurs by two separate mechanisms chemical and electrochemical. The former results in the presence of chemisorbed metal xanthate (or other thiol collector ion) onto the mineral surface. The latter yields an oxidation product (dixanthogen if collector added is xanthate) that is the hydrophobic species adsorbed onto the mineral surface. The chemisorption mechanism is reported to occur with galena, chalcocite and sphalerite minerals, whereas electrochemical oxidation is reportedly the primary mechanism for pyrite, arsenopyrite, and pyrrhotite minerals. The mineral, chalcopyrite, is an example where both the mechanisms are known to be operative. Besides these mechanisms, the adsorption of collectors can be explained from the point of interfacial energies involved between air, mineral, and solution. 

Free gold, which is locked in sulfide minerals, usually pyrite and arsenopyrite this is the most common reason for refractoriness. 

The modern trend is to employ processes based on aqueous oxidation of pyrite and arsenopyrite, and the chemical reactions involved can simplified as ... 

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