Development of framboidal pyrite in the Upper Permian marly limestone of the NE-Hungarian Darnó Hill

            The NE Hungarian Darnó Hill has a complex geology; it is built up by an accrétionary mélange complex, which contains Permian, Triassic and Jurassic sedimentary and magmatic blocks too. The succession can be well correlated with the NW Dinarides, and evidences of the different evolutionary stages of the Neotethyan Ocean (rifting, marginal basin opening, closure) were described too.            Several ore indications are known from this area, but their genesis was by far not well reconstructed, mostly because of the complexity of the geological background. The present study deals with one of these indications found in deep drillings. A framboidal pyrite bearing Permian-Triassic marly limestone series was investigated, which was described earlier as a possible analogy of the Polish-German copper shales (Kupferschiefer).            Based on detailed microscopic, EPMA and whole rock geochemical analyses, it was found, that besides the framboidal pyrite, euhedral pyrite overgrowths (both contain high amount of Au), disseminated euhedral and anhedral pyrite (which do not form framboids or overgrowths), anhedral chalcopyrite, galena and sphalerite were also found, causing a slightly enriched total metal content of 100-200 ppm. The minerals were formed under reducing, anoxic marine conditions, in more steps; after the synsedimentary processes, sulphides formed during early diagenetic/hydrothermal processes too. The found characteristics are typical to the weakly mineralized type of the Kupferschiefer.</p

New Results and Advances in PGE Mineralogy in Ni-Cu-Cr-PGE Ore Systems

The book (Special Issue) presents impressive new results related to a wide spectrum of occurrences of platinum-group minerals (PGM) and natural compounds enriched in platinum-group elements (PGE), which are associated with various complexes and deposits, such as Uralian-Alaskan-type complexes, layered intrusions and placers. The geographical locations of the involved deposits and complexes include, on a truly international scale, different areas of the Urals, Western and Eastern Sayans and Gornaya Shoria in Siberia, Southern Central Asian Orogenic Belt in China, Northern Michigan, USA, South Africa and Zimbabwe, etc. Of particular interest is the first description of a new species of PGM, thalhammerite (approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association), which is a new species of palladium-silver sulfobismuthide discovered in the Noril’sk region of Russia. Additionally, comprehensive reviews, on compositional variations in Pt–Fe alloy minerals and processes of transformations of PGM in exogenic environments, are presented which will also attract attention from international readers

Tiberiobardiite, Cu9Al(SiO3OH)2(OH)12(H2O)6(SO4)1.5·10H2O, a new mineral related to chalcophyllite from the cretaio Cu prospect, massa marittima, grosseto (Tuscany, Italy): Occurrence and crystal structure

The new mineral species tiberiobardiite, ideally Cu9Al(SiO3OH)2(OH)12(H2O)6(SO4)1.5·10H2O, has been discovered in the Cretaio Cu prospect, Massa Marittima, Grosseto, Tuscany, Italy, as very rare, light green, vitreous, tabular 0001, pseudo-hexagonal crystals, up to 200 µm in size and 5 µm in thickness, associated with brochantite. Electron microprobe analysis gave (in wt %, average of 5 spot analyses): SO3 10.37, P2O5 3.41, As2O5 0.05, SiO2 8.13, Al2O3 5.54, Fe2O3 0.74, CuO 62.05, and ZnO 0.03, for a total of 90.32. Based on an idealized O content of 42 atoms per formula unit, assuming the presence of 16 H2O groups and 13.5 cations (without H), the empirical formula of tiberiobardiite is (Cu8.69Al0.21Fe0.10)Σ9.00Al1.00(Si1.51P0.54)Σ2.05S1.44O12.53(OH)13.47·16H2O. The main diffraction lines, corresponding to multiple hkl indices, are [d in Å (relative visual intensity)]: 9.4 (s), 4.67 (s), 2.576 (m), 2.330 (m), and 2.041 (mw). The crystal structure study revealed tiberiobardiite to be trigonal, space group R 3, with unit-cell parameters a = 10.6860(4), c = 28.3239(10) Å, V = 2801.0(2) Å3, and Z = 3. The crystal structure was refined to a final R1 = 0.060 for 1747 reflections with Fo > 4σ (Fo) and 99 refined parameters. Tiberiobardiite is the Si-analogue of chalcophyllite, with Si4+ replacing As5+ through the coupled substitution As5+ + O2− = Si4+ + (OH)−. The name tiberiobardiite honors Tiberio Bardi (b. 1960) for his contribution to the study of the mineralogy of Tuscany

Ferdowsiite from the Monte Arsiccio mine, Apuan Alps, Tuscany (Italy): occurrence and crystal structure

A new finding of ferdowsiite, ideally Ag8Sb5As3S16, from the Monte Arsiccio mine, Apuan Alps, Tuscany (Italy) is reported. Ferdowsiite occurs as black euhedral crystals, up to 0.3 mm in size, associated with arsiccioite, boscardinite, and chabournéite in small vugs of baryte + dolomite veins embedded in the pyrite-rich metadolostone close to the contact with the baryte + pyrite ore body. Electron microprobe data gave (wt% - mean of nine spot analyses): Ag 39.03(36), Pb 0.24(3), As 10.63(18), Sb 26.57(9), S 23.71(14), Cl 0.04(1), total 100.22(41). On the basis of ΣMe = 16 apfu, the chemical formula is Ag8.01(5)Pb0.03(1) Sb4.83(2)As3.14(4)S16.36(15)Cl0.03(1). The crystal structure of ferdowsiite has been refined in the space group P21/n, with unit-cell parameters a = 8.6573(4), b = 5.7896(3), c = 13.7866(7) Å, β = 96.122(2)°, V = 687.08(6) Å3, Z = 1. The R1 factor converged to 0.024 on the basis of 1898 reflections with Fo > 4σ(Fo) and 75 parameters

Fluid inclusion study of the Boccassuolo VMS-related stockwork deposit (Northern-Apennine ophiolites, Italy)

Several Cyprus-type volcanogenic massive sulphide (VMS) deposits are found in the Jurassic ophiolitic series of the Northern Apennines. Stratabound, stratiform and stockwork deposits were formed in the western limb of the Neotethys (Ligurian Ocean) and are found today in basalt, gabbro and serpentinised peridotite host rocks. The studied stockwork deposit at Boccassuolo is found in basalt and basalt breccia. Detailed petrography, fluid inclusion study, Raman spectroscopy analyses and chlorite thermometry calculations were used to determine the P, T, X conditions of the fluid circulation system. The veins contain three quartz generations, calcite, chlorite, epidote and sericite as gangue minerals and pyrite, chalcopyrite, sphalerite, pyrrhotite and galena as ore minerals. Based on the fluid inclusion study, the earlier defined three vein types (1., 2. and 3.) precipitated from the same type of evolving fluid, though at slightly different stratigraphical positions. The determined ranges of temperature (370 60°C), salinity (6.2 11.4 NaCl equiv. wt%), pressure (30-44 MPa) ranges and methane content (average 0.28 mol/kg) suggest an evolved seawater origin for the hydrothermal fluid, modified by fluid-rock interaction and possibly by mixing of magmatic volatile. The fluid characteristics and the mineralogical observations have proven a slightly distal position in relation to the centre of the fluid flow for all studied locations, but less and more distal blocks were also recognised. The temporal evolution of the system developed into a low temperature event, occurring after the main mineral stage, but still participating to the same process as a whole.</p

Crystal-chemistry of sulfates from the Apuan Alps, Tuscany, Italy. VIII. New data on khademite, Al(SO4)F(H2O)5

AbstractKhademite, ideally Al(SO4)F(H2O)5, from the Monte Arsiccio mine, Apuan Alps, Tuscany, Italy, has been characterised through quantitative electron microprobe analysis, micro-Raman spectroscopy and single-crystal X-ray diffraction. Khademite occurs as colourless to whitish tabular crystals, up to 5 mm. Electron microprobe analysis (in wt.%, average of 20 spot analyses) gave: SO3 35.43, Al2O3 21.27, F 6.92, H2Ocalc 39.73, sum 103.35, –O = F 2.92, total 100.43. On the basis of 10 anions per formula unit, assuming the occurrence of 5 H2O groups and 1 (F+OH) atom per formula unit, its chemical formula can be written as Al0.96S1.02O4[F0.84(OH)0.16]Σ1.00⋅5H2O. The Raman spectrum of khademite is characterised by the occurrence of vibrational modes of SO4 groups and by broad and strong bands due to the O–H stretching modes. Khademite is orthorhombic, space group Pcab, with unit-cell parameters a = 11.1713(2), b = 13.0432(3), c = 10.8815(2) Å, V = 1585.54(5) Å3 and Z = 8. The crystal structure refinement converged to R1 = 0.0293 on the basis of 2359 unique reflections with Fo > 4σ(Fo) and 152 refined parameters. The crystal structure of khademite is characterised by the alternation, along b, of two distinct kinds of {010} layers, one formed by [001] rows of isolated Al-centred octahedra, connected to each other through H bonds, and the other showing isolated SO4 groups. Along b, oxygen atoms belonging to SO4 groups act as acceptor of H bonds from H2O groups coordinating Al atoms. The new data improved the description of the H bonds in khademite and led us to discuss about the possible existence of its (OH)-analogue, rostite. In addition, Raman spectroscopic data were collected on the same crystal used for the crystal-chemical characterisation, allowing a comparison with previous results

Progress in the knowledge of 'ruby silvers': New structural and chemical data of pyrostilpnite, Ag3SbS3

AbstractThe crystal structure of pyrostilpnite from the Plaka mine, Lavrion Mining District, Greece, was refined in the space group P21/c to a final R1 index of 0.0283 on the basis of 2047 reflections with Fo > 4σ(Fo) and 65 refined parameters. Unit-cell parameters of the crystal examined are a = 6.8629(6), b = 15.8800(14), c = 6.2711(5) Å, β = 117.087(2)°, V = 608.48(9) Å3 and Z = 4. Chemical data agree with the stoichiometric formula Ag3SbS3. The crystal structure reported previously was confirmed, although a higher precision of refinement was achieved. It can be described as formed by {010} slabs running along c and connected along a through relatively longer Ag–S bonds. The analysis of the atomic displacement parameters together with a refinement with higher order tensors in the expression of the structure factors revealed no hint for pyrostilpnite as an ionic conductor. A historical background of the 'ruby silvers' is also reported

Derbylite and graeserite from the Monte Arsiccio mine (Apuan Alps, Tuscany, Italy): occurrence and crystal-chemistry

New occurrences of derbylite, Fe2+xFe3+4-2xTi4+3+xSb3+O13(OH), and graeserite, Fe2+xFe3+4-2xTi4+3+xAs3+O13(OH), have been identified in the Monte Arsiccio mine, Apuan Alps (Tuscany, Italy). Derbylite occurs as prismatic to acicular black crystals in carbonate veins.Iron and Ti are replaced by V (up to 0.29 atoms per formula unit, apfu) and minor Cr (up to0.4 apfu). Mössbauer spectroscopy confirmed the occurrence of Fe 2+ (up to 0.73 apfu), along with Fe 3+ . The Sb/(As+Sb) atomic ratio range between 0.73 and 0.82. Minor Ba and Pb (up to 0.04 apfu) occur. Derbylite is monoclinic, space group P21/m, with unit-cell parameters a 7.1690(3), b 14.3515(7), c 4.9867(2) Å, β 104.820(3)°, V 495.99(4) Å 3 . The crystal structure was refined to R1 = 0.0352 for 1955 reflections with Fo &gt; 4σ(Fo). Graeserite occurs as prismatic to tabular black crystals, usually twinned, in carbonate veins or as as porphyroblasts in schist. Graeserite in the first kind of assemblage is V-rich (up to 0.66 apfu), whereas it is V-poor in the second one (0.03 apfu). Along with minor Cr (up to 0.06 apfu), this element replaces Fe and Ti. The occurrence of Fe 2+ (up to 0.68 apfu) is confirmed by Mössbauer spectroscopy. Arsenic is dominant over Sb and detectable amounts of Ba and Pb have been measured (up to 0.27 apfu). Graeserite is monoclinic, space group C2/m. Unit-cell parameters are a 5.0225(7), b 14.3114(18), c 7.1743(9) Å, β 104.878(3)°, V 498.39(11) Å 3 and a 5.0275(4), b 14.2668(11), c 7.1663(5) Å, β 105.123(4)°, V 496.21(7) Å3 . The crystal structures of two graeserite samples were refined to R1 = 0.0399 and 0.0237 for 428 and 1081 reflections with Fo &gt; 4σ(Fo), respectively. Derbylite and graeserite have homeotypic relations. They share the same tunnel structure, characterized by an octahedral framework and cuboctahedral cavities, hosting (As/Sb)O3 groups and (Ba/Pb) atom