Arsenical pyrite

Each of these elements occurs naturally as a sulphide ore arsenic as realgar As S,, orpiment As, Sg and arsenical pyrites with approximate formula FeAsS antimony as stibnite Sb2S3 and bismuth as B12S3. 

Native Antimony. In 1748 Anton von Svab found that the so-called arsenical pyrite from tire Sala mine in Sweden was native antimony (76, 79). In a review in 1781 of Torbem Bergman s dissertation on the wet assay of minerals, one finds the statement that the native antimony (Spiessglaskonig) discovered by von Svab is also found, although but rarely, outside Sweden in a quartzose matrix (80). 

In 1863 Reich began a search for thallium in some Freiberg zinc ores from the Himmelsfurst mine consisting mainly of arsenical pyrites, blende, lead glance, silica, manganese, copper, and small amounts of tin and cadmium (19, 43). After roasting the blende to remove most of the sulfur and arsenic, he decomposed it with hydrochloric acid (47). When Clemens Winkler, who was then a metallurgist in the Saxon smalt works, visited Professor Reich in 1863, the latter showed him a straw-yellow precipitate and said, This is the sulfide of a new element (52). Because of his colorblindness, however, Reich entrusted the spectroscopic examination to his assistant, Richter. 

Another variety °f arsenical pyrites is known nnder the technical name Demote, differing from the above in having cobalt as a constituent. Its analysis from different localities does not vary much, as the following two examples show... 

The most abundant mineral of arsenic is arsenopyrite, arsenical pyrites or mispickel,9 FeS2.FeAs2, which with other metallic arsenides and sulphides is found usually in igneous rocks. It occurs in veins near Freiburg (Germany), and in beds at Joachimsthal (Bohemia), Tuna-berg (Sweden) and Skutterud (Norway). It is associated with tin, and... 

Pyrite is the most common sulfide mineral. It is a major contributor to the formation of mine drainage and sulfate-rich natural runoff. The oxidation of pyrite and other Fe(II) sulfides (e.g. marcasite and pyrrhotite) involves both iron and sulfur, as well as any arsenic impurities. Activation energies suggest that surface reactions dominate the oxidation of pyrite (Lengke and Tempel, 2005). Furthermore, evidence from pyrites in coal and ore deposits suggests that arsenian pyrite is more susceptible to oxidation from weathering than low-arsenic pyrite (Savage et al., 2000, 1239). 

The phosphides, arsenides, and antimonides of the other metals are usually dark-coloured substances, with more or less metallic lustre, and therefore conductors of electricity. Some of them occur native for example, smaltine, CoAs2, a common ore of cobalt, forming silver-white crystals copper-nickel, NiAs, red lustrous crystals, and one of the chief nickel ores speiss, a deposit formed in the pots in which smaltine and copper-nickel are fused with potassium carbonate and silica, in the preparation of smalt, a blue glass containing cobalt its formula appears to be Ni8As2. Mispickel, or arsenical pyrites, is a white lustrous substance, of the formula FeSAs. 

Arsenical pyrites 8 or mispickel, FeS2.FeAs2, containing 34 per cent, of iron, occurs in rhombic crystals, with frequent twinning, and of the following parameters —... 

Arsenical mundic > Arsenical pyrites J FeS2.FeAs2 6-6 4 5 5-6... 

Iron thio-arsenide, FeAsS, or FeS2.FeAs2, occurs in nature as the mineral mispichel, arsenical pyrites or arsenopyrite (see p. 24, where crystallographic data are given). If cobalt is also present, the mineral is known as glaucodote, (Fe, Co)AsS. When the arsenide is in excess, the mineral is called pacite, FeS 2.4FeAs2. 

On an industrial scale realgar has been prepared by the reaction between sulfur and an excess of elemental arsenic or AS2O3. Other commercial procedure involves the sublimation of a mixture of pyrites (FeS2), arsenopyrite (FeAsS), or the heating of arsenical pyrites, but these methods yield an impure product. 

MARCASITA ALBA — White Marcasite, i.e.. White Arsenical Pyrites. 

VENAE DURISSIMAE NONUS — A Knot of very hard Ore, Mispickel, possibly also Arsenical Pyrites. 

The principal ore of arsenic (5 x 10 % of earth s crust) is arsenical pyrites, FeAsS, but the element occurs commonly with nickel, copper and tin As40g is recovered from flue-dusts collected during the extraction of these metals. Sublimation in the presence of galena, which prevents the formation of arsenites, purifies the oxide this is reduced to arsenic with carbon in a cast iron retort. The element itself has few uses about 0.5% added to lead increases the surface tension of the molten metal and allows spherical lead-shot to be produced. The principal commercial form is the so-called white arsenic, As Og. Arsenic compounds are used mainly for their toxicity arsenical insecticides have been much used. 

In contrast to the evidence for a late diagenetic timing of arsenic addition, one observation may indicate relatively early introduction of arsenic in the depositional history of the coal beds. As illustrated in Fig. 17 arsenian pyrite locally fills cell lumens (the cavities bounded by the cell wall) of coalified plant debris. These cell lumens, if unfilled, are crushed during burial. Therefore, unless the arsenian (> 0.1 wt. % arsenic) pyrite is a replacement of earlier mineral phase, the presence of arsenian pyrite in uncmshed lumens argues for a relatively early formation. 

Carlson, L, Lindstrom, E. B., Hallberg, K. B., and Tuovinen, O. H., 1992, Solid phase products of bacterial oxidation of arsenical pyrite Applied and Environmental Microbiology, v. 58, p. 1046-1049. 

The arsenic and iron in solution did not reflect the full extent to which the arsenopyrite had been oxidized. Acidiflcation of the culture medium in each flask with 1 ml of concentrated HCl at the end of the experiment increased the arsenic concentration in solution 1.6-fold and the iron concentration 4.4-fold in uninoculated flasks and 1.6- and 7.2-fold, respectively, in inoculated flasks. The increase in dissolved As and Fe on acidification suggests that a portion of the mobilized iron and arsenic was precipitated as iron arsenate and arsenite in inoculated as well as uninoculated flasks. The weight ratios of Fe/As were always higher over 21 days in uninoculated flasks than in inoculated flasks, and in both types of flasks dropped in the first few days of incubation and then increased again. Precipitation of ferric arsenate (scorodite) as well as potassium jarosite [KFcs (804)2(011)6] in bacterial arsenical pyrite oxidation was reported by Carlson et al.(35). 

L Carlson, EB Lindstrom, KB Hallberg, OH Tuovinen. Solid-phase products of bacterial oxidation of arsenical pyrite. Appl Environ Microbiol 58 1046-1049, 1992. WD Cassity, B Pesic. Interactions of Thiobacillus ferrooxidans with arsenite, arsenate and arsenopyrite. In R Amils, A Ballester, eds. Biohydrometallurgy and the Environment Toward the Mining of the 21st Century, Part A. Amsterdam Elsevier, 1999, pp 521-532. 

Davyds interest in minerals went back to his Penzance days. In a paper in i8i8 he says of the Wherry Mine, a mile from Penzance and with its workings entirely under the sea I have seen in the refuse heaps, blende, oxide of uranium, oxide of titanium and of iron pechblende [pitchblende], nickel, and arsenical pyrites and in a single piece of the vein of a few inches square many of these substances might be found imbedded in quartz or chlorite. ... 

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