SR-FTiR microscopy and FTIR imaging in the earth sciences

During the last decades, several books have been devoted to the application of spectroscopic methods in mineralogy. Several short courses and meetings have addressed particular aspects of spectroscopy, such as the analysis of hydrous components in minerals and Earth materials. In these books, complete treatment of the infrared theory and practical aspects of instrumentation and methods, along with an exhaustive list of references, can be found. The present chapter is intended to cover those aspects of infrared spectroscopy that have been developed in the past decade and are not included in earlier reviews such as Volume 18 of Reviews in Mineralogy. These new topics involve primarily: (1) the use of synchrotron radiation (SR), which, although not a routine method, is now rather extensively applied in infrared studies, in particular those requiring ultimate spatial and time resolution and the analysis of extremely small samples (a few tens of micrometers); (2) the development of imaging techniques also for foreseen time resolved studies of geo-mineralogical processes and environmental studies.Comment: 36 pages, 24 figures - Reviews in Mineralogy & Geochemistry - Vol. 78 (2013) in pres

A multi-methodological study of the (K,Ca)-variety of the zeolite merlinoite

A multi-methodological study of the (K,Ca)-variety of the zeolite merlinoite from Fosso Attici, Sacrofano, Italy was carried out on the basis of electron microprobe analysis in wavelength dispersive mode, singlecrystal X-ray diffraction (at 100 K), Raman and infrared spectroscopy. The chemical formula of the merlinoite from Fosso Attici is (Na0.37K5.69)\u3a3=6.06(Mg0.01Ca1.93Ba0.40)\u3a3=2.34(Fe3+0.02Al10.55Si21.38)\u3a3=31.9O64\u38719.6H2O, compatible with the ideal chemical formula K6Ca2[Al10Si22O64]\u38720H2O. Anisotropic structure refinements confirmed the symmetry and the framework model previously reported (space group Immm, a = 14.066(5),b = 14.111(5), c = 9.943(3) \uc5 at 100 K). Refinement converged with four cationic sites and sixH2Osites; refined bond distances of the framework tetrahedra suggest a highly disordered Si/ Al-distribution. The Raman spectrum of merlinoite (collected between 100 and 4000 cm 121) is dominated by a doublet of bands between 496\u2013422 cm 121, assigned to tetrahedral T\u2013O\u2013T symmetric bending modes. T\u2013O\u2013T antisymmetric stretching is also observed; stretching and bending modes of the H2O molecules are only clearly visiblewhen using a blue laser. The single-crystal near-infrared spectrum shows a very weak band at 6823 cm 121, assigned to the first overtone of the O\u2013H stretching mode, and a band at 5209 cm 121, due to the combination of H2O stretching and bendingmodes.Avery broad and convoluted absorption, extending from 3700 to 3000 cm 121 occurs in the H2O stretching region, while the \u3bd2 bending mode of H2O is found at 1649 cm 121. The powder midinfrared spectrum of merlinoite between 400\u20131300 cm 121 is dominated by tetrahedral T\u2013O\u2013T symmetric and antisymmetric stretches. Raman and Fourier-transform infrared spectroscopy spectra of merlinoite and phillipsite provide a quick identification tool for these zeolites, which are often confused due to their close similarity

Morpho-Mineralogical and Bio-Geochemical Description of Cave Manganese Stromatolite-Like Patinas (Grotta del Cervo, Central Italy) and Hints on Their Paleohydrological-Driven Genesis

Caves are dark subsurface environments with relatively constant temperatures that allow studying bio-mineralization processes and paleoenvironmental or climate changes in optimal conditions. In the extreme and oligotrophic cave environment, manganese patinas having stromatolite-like features are uncommon. Here we provide the first detailed mineralogical, geochemical, and microbiological investigation of fine-grained and poorly crystalline MnFe stromatolite-like wall patinas formed in a deep-cave environment in Italy. These mineralizations, about 3 mm thick, consist of an alternation of Mn-layers and Fe-lenses. We show that the microbial communities' composition is dominated by Mn-oxidizing bacteria, such as Bacillus, Flavobacterium, and Pseudomonas. Our multidisciplinary investigation, integrating data from different analytical techniques (i.e., optical microscopy, SEM-EDS, μXRF, XRPD, FT-IR, Raman spectroscopy, and DNA sequencing), revealed peculiar chemical, mineralogical, and biological features: 1) A cyclical oscillation of Mn and Fe along the growth of the patinas. We propose that this oscillation represents the shift between oxic and suboxic conditions related to different phases occurring during paleo-flood events; 2) A typical spatial distribution of mineralogy and oxidation state of Mn, bacterial imprints, detrital content, and stromatolite-like morphologies along the Mn-layers. We propose that this distribution is controlled by the local hydraulic regime of the paleo-floods, which, in turn, is directly related to the morphology of the wall surface. Under less turbulent conditions, the combination of clay mineral catalysis and biological oxidation produced vernadite, a poor-crystalline phyllomanganate with a low average oxidation state of Mn, and branched columnar stromatolite-like morphologies. On the other hand, under more turbulent conditions, the sedimentation of clay minerals and microbial communities' development are both inhibited. In this local environment, a lower oxidation rate of Mn2+ favored the formation of todorokite and/or ranciéite, two compounds with a high average oxidation state of Mn, and flat-laminated or columnar stromatolite-like morphologies

Nuovi dati sulla dietrichite di Boccheggiano, Grosseto

During the reinvestigation of sulfate specimens at the Mineralogical Museum of the University of Rome "La Sapienza", a specimen classified as “halotrichite”, from the now closed pyrite mine of Boccheggiano (Grosseto), which is not hygroscopic unlike the other halotrichite specimens, has been identified as dietrichite. Unlike all previously studied dietrichite, the mineral we investigated is very close to the ideal chemical composition. In fact, its chemical composition, determined by means of ICP and thermogravimetric analyses, is (Zn0,93Fe0,07)Al2(SO4)4 · 22H2O. Dietrichite of this specimen forms both sub-millimetric whitish acicular crystals and white concretions. Crystals are prismatic and sometimes form parallel bundles, showing a spiral bending. The structure refinement has been performed by using Rietveld method on the collected powder diffraction data. Structure data confirm that dietrichite is isostructural with apjohnite and pickeringite

THE CRYSTAL STRUCTURE OF DIETRICHITE, IDEALLY ZnAl2(SO4)4 x 22H2O, A MEMBER OF THE HALOTRICHITE GROUP

PUBBLICATO SU PLINIU

Datolite: a new occurrence in volcanic ejecta (Pitigliano, Toscana, Italy) and crystal-structure refinement

This paper describes the first occurrence of datolite in a volcanic ejectum collected at Pitigliano, Vulsini volcanic complex, Toscana, Italy. The studied specimen was sampled within the pyroclastic levels erupted during one of the several eruptive phases of the Latera caldera in the Roman Comagmatic region (253 - 166 ka). The host rock is massive, with a syenitic appearance, and consists of predominant sanidine, both as fine-grained groundmass and phenocrystals up to 1 cm long. Associated minerals are andraditic garnet, clinopyroxene (augite), biotite, iron oxide and vishnevite. Datolite occurs within vugs in the ejectum as well-formed, transparent, colourless crystals, with stubby prismatic shape; the crystals are about 0.5 mm in maximum diameter. The crystal structure of datolite from Pitigliano has been refined in the P21/c space group to R = 2.18%. Cell dimensions are: a (Å) = 4.8318(4), b (Å) = 7.6116(3), c (Å) = 9.6380(2), β (°) = 90.141(4), V (Å3) = 354.46(3). The chemical composition is (Ca2.006K0.001)∑2.007 (Fe0.007Mn0.004Mg0.002)∑0.013 (B1.986Si1.988Al0.026)∑4.000O8 (OH1.962O0.026F0.012)∑2.000 and the density calculated on the basis of composition and cell dimensions is Dc = 3.00 g/cm3

New crystal-chemical and structural data of dietrichite, ideally ZnAl2(SO4)4 x 22H2O, a member of the halotrichite group

New crystal chemical and structural data of a sample of dietrichite, ideally ZnAl2(SO4)4· 22H2O, from the pyrite mine of Boccheggiano, Grosseto, Italy, are reported. This sample, unlike holotype dietrichite, is very close to the ideal chemical composition, in fact combined ICP and thermogravimetry indicate a formula (Zn0.98Fe0.07)Al1.91(SO4)4.03 · 21.88H2O based on 38O. The crystal structure has been refined by the Rietveld method on transmission Xray powder diffraction data (Rp = 4.13%, Rwp = 5.44%, RB = 4.66%). Dietrichite is monoclinic P21/c, Z =4, a = 6.1757(2), b = 24.262(1), c = 21.206(1) Å, = 100.436(3)°. The structure of dietrichite consists of one ZnO(H2O)5 octahedron, two independent Al(H2O)6 octahedra, and four independent SO4 tetrahedra per asymmetric unit. The only direct connection between polyhedra is by sharing of an oxygen atom, O(16), between S(4) and Zn. The structure contains 22 water molecules, 17 of which are octahedrally coordinated with Zn and Al cations whereas the remaining five molecules are only linked via hydrogen bonds to Oor other H2O molecules. Hexagonal channels, running along [100], originate from a regular alternation of one ZnO(H2O)5 octahedron, two Al(H2O)6 octahedra, and three SO4 tetrahedra. Within thestructure two types of channels may be identified, the first one containing three and the second two H2O molecules. Band positions of the IR spectrum of dietrichite are consistent with those of reference data

Datolite: a new occurrence in volcanic ejecta (Pitigliano, Tuscany, Italy) and crystal-structure refinement

This paper describes the first occurrence of datolite in a volcanic ejectum collected at Pitigliano, Vulsini volcanic complex, Toscana, Italy. The studied specimen was sampled within the pyroclastic levels erupted during one of the several eruptive phases of the Latera caldera in the Roman Comagmatic region (253 - 166 ka). The host rock is massive, with a syenitic appearance, and consists of predominant sanidine, both as fine-grained groundmass and phenocrystals up to 1 cm long. Associated minerals are andraditic garnet, clinopyroxene (augite), biotite, iron oxide and vishnevite. Datolite occurs within vugs in the ejectum as well-formed, transparent, colourless crystals, with stubby prismatic shape; the crystals are about 0.5 mm in maximum diameter. The crystal structure of datolite from Pitigliano has been refined in the P21/c space group to R = 2.18%. Cell dimensions are: a (Å) = 4.8318(4), b (Å) = 7.6116(3), c (Å) = 9.6380(2), b (°) = 90.141(4), V (Å3) = 354.46(3). The chemical composition is (Ca2.006K0.001)Σ2.007(Fe0.007Mn0.004Mg0.002)Σ0.013(B1.986Si1.988Al0.026)Σ4.000O8(OH1.962O0.026F0.012)Σ2.000 and the density calculated on the basis of composition and cell dimensions is Dc = 3.00 g/cm3