Sulfide minerals structure

The properties of some sulfide minerals can be discussed in a reasonably satisfactory way by assigning one or another of the structures of Table I to the sulfur atoms. For some minerals the ligancy of the sulfur atom is equal to its covalence, and for others it is greater, the bonds then having fractional bond numbers. It is often necessary to assign a hybrid structure to the sulfur atoms. I shall assume that the covalent bonds indicated in Table I always have the normal amount of covalent character, as given by the... 

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+. 

It is likely that the lead and sulfur atoms in most of the lead sulfarsenites and related minerals have the tercovalent argonic structures Pb—- and S y+, as in galena. Nowacki (1969) has published a valuable summary of results of structural studies of the so-called sulfosalt minerals, in relation to a system of classification of the structures that he has developed. Many structures of sulfide minerals have been determined by him and his coworkers. 

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. 

Where fluids discharge from hot springs and mix with seawater, they cool quickly and precipitate clouds of fine-grained minerals. The clouds are commonly black with metal sulfides, giving rise to the term black smokers. Some vents give off clouds of white anhydrite these are known as white smokers. Structures composed of chemical precipitates tend to form at the vents, where the hot fluids discharge into the ocean. The structures can extend upward into the ocean for several meters or more, and are composed largely of anhydrite and, in some cases, sulfide minerals. 

High productivity of dispersion fiows P ) for the major associated elements (Sn, Pb, Zn, Cu) that are typical for cassiterite-sulfide mineralization have been established for the Belaya Sopka Volcano-Plutonic Structure that made the like-named mountain range a high, first-priority target (Ananchenko 1982). 

The F1/F2 sheath-like fold structures control the distribution of sulfide mineralization in the noses of the F2 parasitic folds. 

The sulfide minerals have structures based largely upon covalent bonds between the sulfur atoms and other atoms in the substances. In some of the minerals the bonds resonate among alternative positions, and in some there are also metal-metal bonds, conferring metallic properties, especially metallic luster, upon them. 

Many sulfide minerals have structures closely related to those of sphalerite and wurtzite. Chalcopyrite, CuFeS, is an example (Fig. 11-21). Its structure 0 is a tetragonal superstructure of sphalerite, with the copper and iron atoms in the zinc positions of sphalerite. 

The selection of this structure, in which the V—S—Cu bond angle has the value 70°32, rather than the sphalerite superstructure with tetrahedral angles, is surprising. It is likely that in this sulfide mineral, as well as in the others, the sulfur atom is to be described as... 

Many other structures of sulfide minerals have been determined. Most of them conform reasonably well to the structural principles described in this book, but some have surprising features that have not yet been incorporated in the system of structural chemistry,84 and in general the reasons for the choice of one structure rather than another are not yet evident. The general structure theory of the sulfide minerals still awaits formulation. 

Vaughan, D. J. Tossell, J. A. (1983) Electronic structures of sulfide minerals -theory and experiment. Phys. Chem. Minerals, 9, 253-62. 

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