Sphalerite phase

Farneth et al. have investigated the mechanism of the solid-state conversion of a series of II-VI precursors of general formula (R4N )4[S4Mio(SPh)i6]" (R = Me, Et M = Gd, Zn) to the bulk metal sulphide structure. The transformation, as followed by combined TGA and mass spectroscopy, proceeds in two discrete reaction steps. In the case of cadmium derivative, the loss of countercations around 200 °G produces a new molecular solid, which was characterized (X-ray) to be GdioSi6Phi2. This intermediate composition gave a broad X-ray diffraction pattern that indicated very small (<25 A) sphalerite-phase (cubic) crystals of GdS. The second decomposition reaction eliminates S6Phi2 around 350 °G and produces phase-pure GdS (wurtzite) (Equation (5)). 

Sonoelectrochemical synthesis has recently been used for the preparation of semiconductor nanocrystalline powders. In the sonoelectrochemical method, the ultrasound horn acts as both cathode and ultrasound emitter. This technique was used for preparing metal powders [65] and was extended to CdTe, although details of the CdTe particle size were not given [66]. CdSe nanocrystalline powders have been prepared by pulsed sonoelectrochemical reduction from an aqueous selenosulfate solution. The crystal size could be varied from X-ray amorphous up to 9 nm (sphalerite phase) by controlling the various electrodeposition and sonic parameters [67]. Crystal size was smaller for lower preparation temperatures, higher ultrasound intensity, and shorter current pulse width. These dependencies could be explained based on a pulse of electric... 

Amorphous films of the (Zn,Fe)S semiconductor have been obtained by electrodeposition on TO substrates from a diethylene glycol solution containing Ss, FeCl2, and ZnCl2 reagents [102]. The films were annealed at 285 °C in argon to give sphalerite and pyrrhotite (Zn,Fe)S phases. A direct relationship was observed... 

Stannite is the most common tin sulfide mineral in the ore deposits associated with tin mineralization. This mineral sometimes contains appreciable amounts of zinc, together with iron. Several workers have suggested that the zinc and iron contents of stannite are related to temperature. With respect to the study of the phase relationships in the pseudobinary stannite-kesterite system. Springer (1972) proposed zincic stannite as a possible geothermometer mainly based on the chemical compositions of the two exsolved phases (stannite and kesterite). Nekrasov et al. (1979) and Nakamura and Shima (1982) experimentally determined the temperature dependency of iron and zinc partitioning between stannite and sphalerite. 

Barton, P.B. Jr. and Toulmin, P. Ill (1966) Phase relations involving sphalerite in the Fe-Zn-S system. Econ. Geol, 61, 815-849. 

A few studies on grain size of minerals in midoceanic ridge chimneys have been published. Feely et al. (1987) described the grain size of mineral particles in the smoke and sediment samples from southern Juan de Fuca Ridge. They report the following grain sizes sphalerite 0.3-100 p.m in diameter (usually less than 20 p.m) pyrite 0.1-10 p.m Fe-Si, Ca-Si phases 5-150 p.m. Converse et al. (1984) reported the grain size... 

Every ionic crystal can formally be regarded as a mutually interconnected composite of two distinct structures cationic sublattice and anionic sublattice, which may or may not have identical symmetry. Silver iodide exhibits two structures thermodynamically stable below 146°C sphalerite (below 137°C) and wurtzite (137-146°C), with a plane-centred I- sublattice. This changes into a body-centred one at 146°C, and it persists up to the melting point of Agl (555°C). On the other hand, the Ag+ sub-lattice is much less stable it collapses at the phase transition temperature (146°C) into a highly disordered, liquid-like system, in which the Ag+ ions are easily mobile over all the 42 theoretically available interstitial sites in the I-sub-lattice. This system shows an Ag+ conductivity of 1.31 S/cm at 146°C (the regular wurtzite modification of Agl has an ionic conductivity of about 10-3 S/cm at this temperature). 

Silurian Mt. Wills Granite. Gold mineralisation is structurally-hosted and accompanied by the presence of pyrite, arsenopyrite, sphalerite, aurostibite, and a variety of sulfosalts (Crohn 1958). Gangue phases include quartz and ferroan dolomite. 

Several cubic structures, therefore, in which (besides 0, 0, 0 0, K, M M, 0, M M, M, 0) one or more of the reported coordinate groups are occupied could be considered as filled-up derivatives of the cubic close-packed structures. The NaCl, CaF2, ZnS (sphalerite), AgMgAs and Li3Bi-type structures could, therefore, be included in this family of derivative structures. For this purpose, however, it may be useful to note that the radii of small spheres which fit exactly into tetrahedral and octahedral holes are, respectively, 0.225. and 0.414... if the radius of the close-packed spheres is 1.0. For a given phase pertaining to one of the aforementioned types (NaCl, ZnS, etc.) if the stated dimensional conditions are not fulfilled, alternative descriptions of the structure may be more convenient than the reported derivation schemes. 

According to Pearson (1972), when a point representing a specific phase has a larger value of the strain parameter than that of a particular contact line, then the contacts corresponding to that line are to be considered compressed, on the basis of the Dx and DY assumed for the components. If, on the other hand, the experimental points lie below a line then those contacts have not been established. Fig. 4.24(a)-(c) represent the data and the trends for a few structure types. For compounds having the cF8-ZnS sphalerite structure it can be seen that the X-Y (Zn-S)... 

Preliminary work has shown that mineralization at Williams Brook includes the sulfide phases pyrite and honey-brown sphalerite. Oxide phases including magnetite and hematite are prevalent throughout the core and heavily concentrated in the first 10 m of the drill... 

Five different vein phases (Types i to V) are recognized at both deposits, aii have variabie amounts of carbonates and quartz gangue. Type i veins contain oniy brecciated quartz and carbonate minerals and at ED are spatially associated with disseminated arsenopyrite, chalcopyrite, pyrrhotite, and pyrite in the mafic host rock. Type II veins in both deposits are partly brecciated and contain 5-80% sulfides of dominantly pyrite, arsenopyrite, and at GB chalcopyrite. Type III veins are quartz-calcite-tetrahedrite-bismuthinite microveins that cut both Types I and II veins. The fine-grained sulfides replace and enclose arsenopyrite and pyrite in Type II veins and are also visible in microfractures within the Type II sulfides. Type IV veins are base-metal rich and characterized by galena, sphalerite, chalcopyrite, pyrite, and stibnite with a maximum width of 20 cm. The Type V veins are late barren-carbonate veins cutting all previous veins and textural features. 

Moh, G. H. The sphalerite-wurtzite inversion, pp. 38-40. In Tin-containing mineral systems, Part. II. Phase relations and mineral assemblages in the Cu-Fe-Zn-Sn-S system. Chem. 

In thick ( 300 pm) crystals of GaN electronic excitons of shallow dopants have been observed in far infrared absorption at 215 cm 1 [44], Interpreted as the ls-2p transition of a residual shallow donor, its binding energy was calculated to be (35.5 0.5) meV. Further modes at 149 and 242 cm 1 have been observed in mixed phase GaN/GaAs in Raman scattering and have been associated with electronic excitations of shallow donors in cubic and sphalerite GaN, respectively [45] see also [46], Far infared absorption at 23.2 cm 1 in magnetic fields has been used to determine the effective electron mass in GaN, m = 0.20 0.005 m, (corrected for polaron effects) in cyclotron resonance [47]. 

The enstatite chondrites formed under extremely reducing conditions, reflected in their strange and unique mineralogy. In addition to the more common sulfide phases, minerals such as niningerite, alabandite, oldhamite, daubreelite, sphalerite,... 

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