ALBERT

Description: 〈div data-abstract-type="normal"〉〈p〉The crystal structure of Ni-rich gordaite–thérèsemagnanite has been determined from a sample collected at pillar 80 in the North mine, Cap Garonne, Var, France. The structure was refined to 〈span〉R〈/span〉〈span〉1〈/span〉 = 0.0693 for 935 reflections with 〈span〉I〈/span〉 〉 2σ(〈span〉I〈/span〉). The mineral is isostructural with gordaite, forming a layered structure with an extensive hydrogen-bonding network. The possible polytypic relationship between gordaite, thérèsemagnanite and guarinoite is also discussed. The guarinoite formula (Zn,Co,Ni)〈span〉6〈/span〉(SO〈span〉4〈/span〉)(OH,Cl)〈span〉10〈/span〉·5H〈span〉2〈/span〉O is also likely to be incorrect and is more likely to be Na(Zn,Co)〈span〉4〈/span〉(SO〈span〉4〈/span〉)(OH)〈span〉6〈/span〉Cl·5–6H〈span〉2〈/span〉O, meaning that guarinoite is equivalent to Co-rich gordaite-2〈span〉H〈/span〉 and would not be a distinct mineral species.〈/p〉〈/div〉

Description: 〈div data-abstract-type="normal"〉〈p〉Frenchvale quarry, once mined for dolomitic marble, contains pink corundum-bearing, quartz-free/-poor, feldspathic gneiss that is unusually sodic (~7% wt.% Na〈span〉2〈/span〉O) and iron-poor (~0.6 wt.% Fe〈span〉2〈/span〉O〈span〉3〈/span〉), but has silica, alumina and immobile trace-element contents resembling those of suspended fluvial particulate matter (e.g. in the Congo River). The protolith of the gneiss, interpreted as a fine-grained clastic sediment deposited offshore, evidently was albitised prior to deformation and regional metamorphism. Variably-altered gneiss samples show a narrow range of δ〈span〉18〈/span〉O〈span〉VSMOW〈/span〉 values (8.1 to 10.7‰) and no systematic differences in bulk O isotope composition as a function of alteration intensity. With the exception of an extensively fuchsitised zone adjacent to a thick (1.2 m), cross-cutting quartz vein that contains H〈span〉2〈/span〉O–NaCl+CO〈span〉2〈/span〉+CH〈span〉4〈/span〉-bearing fluid inclusions, the O isotope data do not support interaction of the gneiss with an externally-derived fluid phase except at low fluid:rock ratio, even where granodiorite occurs in direct contact with the gneiss. Fluid inclusions in the quartz vein have bulk 〈span〉〈span〉〈img data-mimesubtype="gif" data-type="simple" src="http://static.cambridge.org/resource/id/urn:cambridge.org:id:binary:20190522072108342-0385:S0026461X18001652:S0026461X18001652_inline1.gif"〉 〈span data-mathjax-type="texmath"〉 〈/span〉 〈/span〉〈/span〉, 〈span〉〈span〉〈img data-mimesubtype="gif" data-type="simple" src="http://static.cambridge.org/resource/id/urn:cambridge.org:id:binary:20190522072108342-0385:S0026461X18001652:S0026461X18001652_inline2.gif"〉 〈span data-mathjax-type="texmath"〉 〈/span〉 〈/span〉〈/span〉 and 〈span〉〈span〉〈img data-mimesubtype="gif" data-type="simple" src="http://static.cambridge.org/resource/id/urn:cambridge.org:id:binary:20190522072108342-0385:S0026461X18001652:S0026461X18001652_inline3.gif"〉 〈span data-mathjax-type="texmath"〉 〈/span〉 〈/span〉〈/span〉 values (in mol.%) of 99.60, 0.14 and 0.26, respectively, as determined by gas chromatography. Although the protolith of the gneiss was associated with carbonate platformal rocks (now marble), corundum is confined to the feldspathic rocks. These feldspathic rocks lack calc-silicate minerals; they are not skarns. As such, they are distinct from well-known Himalayan sapphire and ruby deposits cited previously as analogues of the Frenchvale corundum occurrence.〈/p〉〈/div〉

Description: 〈div data-abstract-type="normal"〉〈p〉The crystal structure of eztlite has been determined using single-crystal synchrotron X-ray diffraction and supported using electron microprobe analysis and powder diffraction. Eztlite, a secondary tellurium mineral from the Moctezuma mine, Mexico, is monoclinic, space group 〈span〉Cm〈/span〉, with 〈span〉a〈/span〉 = 11.466(2) Å, 〈span〉b〈/span〉 = 19.775(4) Å, 〈span〉c〈/span〉 = 10.497(2) Å, β = 102.62(3)° and 〈span〉V〈/span〉 = 2322.6(9) Å〈span〉3〈/span〉. The chemical formula of eztlite has been revised to 〈span〉〈span〉〈img data-mimesubtype="gif" data-type="simple" src="http://static.cambridge.org/resource/id/urn:cambridge.org:id:binary:20190128104130349-0707:S0026461X18001081:S0026461X18001081_inline1.gif"〉 〈span data-mathjax-type="texmath"〉 〈/span〉 〈/span〉〈/span〉(Te〈span〉4+〈/span〉O〈span〉3〈/span〉)〈span〉3〈/span〉(SO〈span〉4〈/span〉)O〈span〉2〈/span〉Cl from that stated previously as 〈span〉〈span〉〈img data-mimesubtype="gif" data-type="simple" src="http://static.cambridge.org/resource/id/urn:cambridge.org:id:binary:20190128104130349-0707:S0026461X18001081:S0026461X18001081_inline2.gif"〉 〈span data-mathjax-type="texmath"〉 〈/span〉 〈/span〉〈/span〉(Te〈span〉4+〈/span〉O〈span〉3〈/span〉)〈span〉3〈/span〉(Te〈span〉6+〈/span〉O〈span〉6〈/span〉)(OH)〈span〉10〈/span〉·〈span〉n〈/span〉H〈span〉2〈/span〉O. This change has been accepted by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association, Proposal 18-A. Eztlite was reported originally to be a mixed-valence Te oxysalt; however the crystal structure, bond-valence analysis and charge balance considerations clearly show that all Te is tetravalent. Eztlite contains a unique combination of elements and is only the second Te oxysalt to contain both sulfate and chloride. The crystal structure of eztlite contains mitridatite-like layers, with a repeating triangular nonameric [〈span〉〈span〉〈img data-mimesubtype="gif" data-type="simple" src="http://static.cambridge.org/resource/id/urn:cambridge.org:id:binary:20190128104130349-0707:S0026461X18001081:S0026461X18001081_inline3.gif"〉 〈span data-mathjax-type="texmath"〉 〈/span〉 〈/span〉〈/span〉O〈span〉36〈/span〉]〈span〉45–〈/span〉 arrangement formed by nine edge-sharing Fe〈span〉3+〈/span〉O〈span〉6〈/span〉 octahedra, decorated by four trigonal pyramidal Te〈span〉4+〈/span〉O〈span〉3〈/span〉 groups, compared to PO〈span〉4〈/span〉 or AsO〈span〉4〈/span〉 tetrahedra in mitridatite-type minerals. In eztlite, all four tellurite groups associated with one nonamer are orientated with the lone pair of the Te atoms pointing in the same direction, whereas in mitridatite the central tetrahedron is orientated in the opposite direction to the others. In mitridatite-type structures, interlayer connections are formed exclusively 〈span〉via〈/span〉 Ca〈span〉2+〈/span〉 and water molecules, whereas the eztlite interlayer contains Pb〈span〉2+〈/span〉, sulfate tetrahedra and Cl〈span〉–〈/span〉. Interlayer connectivity in eztlite is achieved primarily by connections 〈span〉via〈/span〉 the long bonds of Pbφ〈span〉8〈/span〉 and Pbφ〈span〉9〈/span〉 groups to sulfate tetrahedra and to Cl〈span〉–〈/span〉. Secondary connectivity is 〈span〉via〈/span〉 Te–O and Te–Cl bonds.〈/p〉〈/div〉

Description: 〈div data-abstract-type="normal"〉〈p〉The crystal structure of tlapallite has been determined using single-crystal X-ray diffraction and supported by electron probe micro-analysis, powder diffraction and Raman spectroscopy. Tlapallite is trigonal, space group 〈span〉P〈/span〉321, with 〈span〉a〈/span〉 = 9.1219(17) Å, 〈span〉c〈/span〉 = 11.9320(9) Å and 〈span〉V〈/span〉 = 859.8(3) Å〈span〉3〈/span〉, and was refined to 〈span〉R〈/span〉〈span〉1〈/span〉 = 0.0296 for 786 reflections with 〈span〉I〈/span〉 〉 2σ(〈span〉I〈/span〉). This study resulted from the discovery of well-crystallised tlapallite at the Wildcat prospect, Utah, USA. The chemical formula of tlapallite has been revised to (Ca,Pb)〈span〉3〈/span〉CaCu〈span〉6〈/span〉[Te〈span〉4+〈/span〉〈span〉3〈/span〉Te〈span〉6+〈/span〉O〈span〉12〈/span〉]〈span〉2〈/span〉(Te〈span〉4+〈/span〉O〈span〉3〈/span〉)〈span〉2〈/span〉(SO〈span〉4〈/span〉)〈span〉2〈/span〉·3H〈span〉2〈/span〉O, or more simply (Ca,Pb)〈span〉3〈/span〉CaCu〈span〉6〈/span〉Te〈span〉4+〈/span〉〈span〉8〈/span〉Te〈span〉6+〈/span〉〈span〉2〈/span〉O〈span〉30〈/span〉(SO〈span〉4〈/span〉)〈span〉2〈/span〉·3H〈span〉2〈/span〉O, from H〈span〉6〈/span〉(Ca,Pb)〈span〉2〈/span〉(Cu,Zn)〈span〉3〈/span〉(TeO〈span〉3〈/span〉)〈span〉4〈/span〉(TeO〈span〉6〈/span〉)(SO〈span〉4〈/span〉). The tlapallite structure consists of layers containing distorted Cu〈span〉2+〈/span〉O〈span〉6〈/span〉 octahedra, Te〈span〉6+〈/span〉O〈span〉6〈/span〉 octahedra and Te〈span〉4+〈/span〉O〈span〉4〈/span〉 disphenoids (which together form the new mixed-valence phyllotellurate anion [Te〈span〉4+〈/span〉〈span〉3〈/span〉Te〈span〉6+〈/span〉O〈span〉12〈/span〉]〈span〉12−〈/span〉), Te〈span〉4+〈/span〉O〈span〉3〈/span〉 trigonal pyramids and CaO〈span〉8〈/span〉 polyhedra. SO〈span〉4〈/span〉 tetrahedra, Ca(H〈span〉2〈/span〉O)〈span〉3〈/span〉O〈span〉6〈/span〉 polyhedra and H〈span〉2〈/span〉O groups fill the space between the layers. Tlapallite is only the second naturally occurring compound containing tellurium in both the 4〈span〉+〈/span〉 and 6〈span〉+〈/span〉 oxidation states with a known crystal structure, the other being carlfriesite, CaTe〈span〉4+〈/span〉〈span〉2〈/span〉Te〈span〉6+〈/span〉O〈span〉8〈/span〉. Carlfriesite is the predominant secondary tellurium mineral at the Wildcat prospect. We also present an updated structure for carlfriesite, which has been refined to 〈span〉R〈/span〉〈span〉1〈/span〉 = 0.0230 for 874 reflections with 〈span〉I〈/span〉 〉 2σ(〈span〉I〈/span〉). This updated structural refinement improves upon the one reported previously by refining all atoms anisotropically and presenting models of bond valence and Te〈span〉4+〈/span〉 secondary bonding.〈/p〉〈/div〉

Description: The crystal structure of Ni-rich gordaite–thérèsemagnanite has been determined from a sample collected at pillar 80 in the North mine, Cap Garonne, Var, France. The structure was refined to R1 = 0.0693 for 935 reflections with I > 2σ(I). The mineral is isostructural with gordaite, forming a layered structure with an extensive hydrogen-bonding network. The possible polytypic relationship between gordaite, thérèsemagnanite and guarinoite is also discussed. The guarinoite formula (Zn,Co,Ni)6(SO4)(OH,Cl)10·5H2O is also likely to be incorrect and is more likely to be Na(Zn,Co)4(SO4)(OH)6Cl·5–6H2O, meaning that guarinoite is equivalent to Co-rich gordaite-2H and would not be a distinct mineral species.

Description: The mineral ‘oboyerite’, first described in 1979 from the Grand Central mine, Tombstone, Cochise County, Arizona, USA, has been re-examined. The type specimen from the Natural History Museum, London and a specimen from the Natural History Museum of Los Angeles County (traceable to S. A Williams, who first described ‘oboyerite’) were analysed in this study. The discreditation of ‘oboyerite’ as a valid mineral species has been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (Proposal 19-D). Single-crystal X-ray diffraction, powder X-ray diffraction, electron probe microanalysis and scanning electron microscopy were all employed to show that ‘oboyerite’ is formed of at least two distinct phases, including the lead–tellurium oxysalt minerals ottoite and plumbotellurite. During the course of the discreditation, plumbotellurite was confirmed to be identical to the synthetic compound α-Pb2+Te4+O3. Previously, in some mineralogical literature plumbotellurite was described as orthorhombic with no known crystal structure.

Description: The crystal structure of tlapallite has been determined using single-crystal X-ray diffraction and supported by electron probe micro-analysis, powder diffraction and Raman spectroscopy. Tlapallite is trigonal, space group P321, with a = 9.1219(17) Å, c = 11.9320(9) Å and V = 859.8(3) Å3, and was refined to R1 = 0.0296 for 786 reflections with I 〉 2σ(I). This study resulted from the discovery of well-crystallised tlapallite at the Wildcat prospect, Utah, USA. The chemical formula of tlapallite has been revised to (Ca,Pb)3CaCu6[Te4+3Te6+O12]2(Te4+O3)2(SO4)2·3H2O, or more simply (Ca,Pb)3CaCu6Te4+8Te6+2O30(SO4)2·3H2O, from H6(Ca,Pb)2(Cu,Zn)3(TeO3)4(TeO6)(SO4). The tlapallite structure consists of layers containing distorted Cu2+O6 octahedra, Te6+O6 octahedra and Te4+O4 disphenoids (which together form the new mixed-valence phyllotellurate anion [Te4+3Te6+O12]12−), Te4+O3 trigonal pyramids and CaO8 polyhedra. SO4 tetrahedra, Ca(H2O)3O6 polyhedra and H2O groups fill the space between the layers. Tlapallite is only the second naturally occurring compound containing tellurium in both the 4+ and 6+ oxidation states with a known crystal structure, the other being carlfriesite, CaTe4+2Te6+O8. Carlfriesite is the predominant secondary tellurium mineral at the Wildcat prospect. We also present an updated structure for carlfriesite, which has been refined to R1 = 0.0230 for 874 reflections with I 〉 2σ(I). This updated structural refinement improves upon the one reported previously by refining all atoms anisotropically and presenting models of bond valence and Te4+ secondary bonding.

Description: Frenchvale quarry, once mined for dolomitic marble, contains pink corundum-bearing, quartz-free/-poor, feldspathic gneiss that is unusually sodic (~7% wt.% Na2O) and iron-poor (~0.6 wt.% Fe2O3), but has silica, alumina and immobile trace-element contents resembling those of suspended fluvial particulate matter (e.g. in the Congo River). The protolith of the gneiss, interpreted as a fine-grained clastic sediment deposited offshore, evidently was albitised prior to deformation and regional metamorphism. Variably-altered gneiss samples show a narrow range of δ18OVSMOW values (8.1 to 10.7‰) and no systematic differences in bulk O isotope composition as a function of alteration intensity. With the exception of an extensively fuchsitised zone adjacent to a thick (1.2 m), cross-cutting quartz vein that contains H2O–NaCl+CO2+CH4-bearing fluid inclusions, the O isotope data do not support interaction of the gneiss with an externally-derived fluid phase except at low fluid:rock ratio, even where granodiorite occurs in direct contact with the gneiss. Fluid inclusions in the quartz vein have bulk $X_{{ m H}_2{ m O}}$, $X_{{ m C}{ m O}_{ m 2}}$ and $X_{{ m C}{ m H}_{ m 4}}$ values (in mol.%) of 99.60, 0.14 and 0.26, respectively, as determined by gas chromatography. Although the protolith of the gneiss was associated with carbonate platformal rocks (now marble), corundum is confined to the feldspathic rocks. These feldspathic rocks lack calc-silicate minerals; they are not skarns. As such, they are distinct from well-known Himalayan sapphire and ruby deposits cited previously as analogues of the Frenchvale corundum occurrence.