The new mineral tomiolloite, Al12(Te4+O3)5[(SO3)0.5(SO4)0.5](OH)24; a unique microporous tellurite structure

• Published in: The American mineralogist Vol. 107; no. 12; pp. 2167 - 2175
• Main Authors: Missen, Owen P, Mills, Stuart J, Rumsey, Michael S, Spratt, John, Najorka, Jens, Kampf, Anthony R, Thorne, Brent
• Format: Journal Article
• Language: English
• Published: Washington Mineralogical Society of America 01.12.2022; Walter de Gruyter GmbH
• Subjects: Aluminium; Aluminum; Analytical methods; and utilizations; Bambolla Mine; Chains; Crankshafts; crystal chemistry; crystal structure; Crystals; Diffraction; diffractograms; Electron microprobe; Electron probe microanalysis; Electron probes; Empirical analysis; formula; Frameworks; gold ores; infrared spectra; lattice parameters; metal ores; Mexico; microporous; Microporous materials; Mineralogy; Minerals; Moctezuma; Moctezuma Mexico; New mineral; new minerals; nonsilicates; Notches; Photoelectron spectroscopy; Photoelectrons; Polyhedra; properties; Pyramids; Single crystals; Sonora; Sonora Mexico; space groups; spectra; Structural analysis; Sulfates; Sulfite; sulfites; Sulfur trioxide; Sulphates; synchrotron radiation; Synchrotrons; Tellurite; tellurites; Tellurium; Tellurium dioxide; tellurium oxysalt; Tetrahedra; tomiolloite; Unit cell; X-ray diffraction; X-ray diffraction data
• ISSN: 0003-004X; 1945-3027
• DOI: 10.2138/am-2022-8368

Tomiolloite (IMA2021-019) is a new aluminum tellurite sulfite-sulfate mineral discovered at the Bambolla mine, Moctezuma, Sonora, Mexico, a well-known tellurium (Te) mineral locality. Tomiolloite forms roughly spherical clusters of crystals comprised of very thin, needle-like crystals (1 µm diameter, ∼40 µm length) around a core of small, stubbier, broken crystals. Tomiolloite is generally found growing on tellurite or quartz. The strongest powder X-ray diffraction lines are [dobs Å (Iobs) (hkl)]: 11.667 (89) (100), 8.240 (38) (101), 4.107 (29) (202,211,121), 3.223 (100) (203,302,130), and 2.905 (37) (213,123,222,400). The empirical formula of tomiolloite, as determined by electron microprobe analysis, is (Al10.64 Te1.016+ Fe0.313+ Zn0.04)Σ12 (Te5.004+ Pb0.02)Σ5.02 (S0.494+ S0.496+ Si0.02)Σ1.00 O21.53[(OH)20.86 Cl0.11]Σ20.97, which is simplified to the ideal formula Al12(Te4+O3)5[(SO3)0.5(SO4)0.5](OH)24. Significant Te6+ substitution for Al3+ is observed in tomiolloite, verified by X-ray photoelectron spectroscopy and crystal-structure analysis. The structure of tomiolloite was determined using synchrotron single-crystal X-ray diffraction, showing that tomiolloite is hexagonal and crystallizes in the space-group P63/m, with the unit-cell parameters a=13.3360(19) Å, c=11.604(2) Å, V=1787.3(6) Å3, and Z=2. Tomiolloite has a unique microporous framework structure, which bears a slight similarity to that of zemannite, but it has a much larger cavity diameter (8.85 Å). The framework is built from edge-sharing Mφ6 octahedra (M=Al3+ and Te6+), Te4+O3 trigonal pyramids, and Te4+O4 disphenoids. Mφ6 octahedra edge-share to form crankshaft-shaped chains along c, with Te4+On polyhedra filling notches in the crankshafts and providing linkages between adjacent chains. The framework has an overall positive charge, which is balanced by the presence of both sulfite (SO32-) trigonal pyramids and sulfate (SO42-) tetrahedra in the channels.