MINERALOGICAL CRYSTALLOGRAPHY

Coordinated by Giovanni Ferraris giovanni.ferraris@unito.it

Internationally, the Italian research in the field of Mineralogy ranks at the top positions thanks to its strong crystallographic character, as recently witnessed by the role played by Italian mineralogists in founding and ruling the SIG Mineralogical Crystallography of ECA[1] and the Commission on Inorganic and Mineral Structures of IUCr[2]. Besides, the Italian role in the organization of and contribution to crystallography-oriented symposia and schools organized by the International Mineralogical Association[3] and the European Union of Mineralogy[4] is fundamental. Italy is leader in the characterization of new and rare mineral species[5,6,7,8,9,10,11,12,13], a topic where the structural characterization by X-ray and electron diffraction plays a crucial role. Low crystallinity and complexity of the structures that are met in this type of research, often do not allow the use of automatic methods for structure solution; thus, the development and use of other modern experimental (TEM[9,10,11]; spectroscopy like EXAFS[7,11,14], IR, Mössbauer, NMR, XANES[7,11,14], XPS) and theoretical approaches have been stimulated. Important theoretical contributions have been published in the field of modular crystallography (OD theory, polysomatism, polytypism, twinning, incommensurate structures)[5,9,10,11], an approach applicable to large families of technological materials too. The mentioned spectroscopic methods have been applied also to the study of local geometry, oxidation state and short-range ordering. The experimental results are often supported by theoretical calculations, e.g. molecular dynamics and modelling of crystal structures and of absorption spectra[7,8,10,12,14,15,16].

foto 9

HRTEM image of carlosturanite (after Carlo Sturani, Professor in Torino), cylindrical chrysotile and polygonal serpentine intergrown fibres as seen along the fibre axes. (Deriu, A., Ferraris, G., Belluso, E. Phys. Chem. Minerals, 21, 1994, 222-227).

The crystal-chemical investigation of some main groups of rock-forming minerals (amphiboles[8,10], carbonates[8], feldspars[10,14], garnets[8], micas[7,10,13,15,17], pyroxenes[8,10,18], pyroxenoids[9], serpentines[10,11], spinels[6,10,18], staurolites[8], zeolites[7,9,15,16], including meteorites[11]) is another outstanding feature of the Italian mineralogical crystallography. In particular, this type of research brought to the development of crystallographic investigations at non-ambient conditions (in order to study the stability, transformations and kinetics of phases and to establish state equations) and of detailed crystal-chemical analysis and structure modelling (with the aim to relate cation order and site geometry to the P, T, X conditions of formation)[7,8,9,10,11,15,17,19]. The latter results combine structure refinement, SIMS and IR analysis when light elements are involved[8]. For most of the mentioned groups of minerals, unique databases of crystal-chemical data have been established[8].

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Some of the results obtained by Italian mineralogical crystallographers are of primary interest for materials and environmental sciences, technology and industrial processes, like those concerning the properties of cationic exchange, diffusion, heterogeneous catalysis and gas dehydration of microporous minerals (zeolites[7,15,16], titanosililcates[9,10], layered silicates[7,15]) and the calcium silicates hydrates so important in the chemistry of cement (e.g. the tobermorite group)[9].

Recent pubblications on Mineralogical Crystallography

Alberti A., Cruciani G., Galli E., Merlino S., Millini R., Quartieri S., Vezzalini G., Zanardi S. (2002). Crystal structure of tetragonal and monoclinic polytypes of tschernichite, the natural counterpart of synthetic zeolite Beta. J. Phys. Chem. B 2002, 106, 10277.

Basso R., Lucchetti G., Martinelli A., Palenzona A. (2003). Cavoite, CaV3O7, a new mineral from the Gambatesa mine, northern Apennines, Italy. Eur. J. Mineral., 15: 181.

Benna P., Bruno E. (2003). Single-crystal in situ high-temperature structural investigation of the I1-I2/c phase transition in Ca0.2Sr0.8Al2Si2O8 feldspar. Am. Mineral., 88, 1532.

Bonazzi P., Bindi L., Olmi F., Menchetti S. (2003). How many alacranites do exist? A structural study of non-stoichiometric As8S9-x crystals. European Journal of Mineralogy, 15, 283.

Brigatti, M.F., Guggenheim, S., Poppi, M. (2003). Crystal chemistry of the 1M mica polytype: The octahedral sheet. Am. Mineral., 88, 667.

Cattaneo, A., Gualtieri, A., Artioli, G. (2003). Kinetic study of the dehydroxylation of chrysotile asbestos with temperature by in situ XRPD. Phys. Chem. Min., 30, 177.

Comodi P., Drabek M., Montagnoli M., Rieder M., Weiss Z., Zanazzi P.F. (2003). Pressure-induced phase transition in synthetic trioctahedral Rb-mica. Phys. Chem. Minerals, 30, 198.

Ferraris G., Makovicky E., Merlino S. (2004). Crystallography of Modular Materials. IUCr/Oxford University Press.

Mellini M., Fuchs Y., Viti C., Lemaire C., Linares J., (2002). Insights on the antigorite structure from Mossbauer and FTIR spectroscopies. Eur. J. Mineral., 14, 97.

Merlino S., Bonaccorsi E., Armbruster T. (2001). The real structure of tobermorite 11Å: normal and anomalous forms, OD character and polytypic modifications. Eur. J. Mineral., 13, 577.

Mottana A., Murata T., Wu Z.Y., Marcelli A., Paris E. (1999). The local structure of Ca-Na pyroxenes. II. XANES studies at the Mg and Al K-edges. Phys Chem Minerals, 27, 20.

Oberti R., Della Ventura G., Ottolini L., Hawthorne F.C., Bonazzi P.(2002). Re-definition, nomenclature and crystal-chemistry of the hellandite group. Am. Mineral., 87, 745.

Pavese A., Curetti N., Ferraris G., Ivaldi G., Russo U. (2003). Deprotonation and order-disorder reactions as a function of temperature in a phengite 3T (Cima Pal, western Alps) by neutron diffraction and Mössbauer spectroscopy. Eur. J. Miner., 15, 357.

Quartieri S., Boscherini F., Chaboy J., Dalcini M.C., Oberti R., Zanetti A. (2002). Characterization of trace Nd and Ce site preference and coordination in natural melanites: a combined X-ray diffraction and high-energy XAFS study. Phys Chem Minerals, 29, 495.

Schingaro E., Scordari F., Ventruti G. (2001). Trioctahedral micas-1M from Mt. Vulture (Italy): structural disorder and crystal chemistry. Eur. J. Mineral., 13, 1057.

[1] www.clik.to/ecasig5

[2] http://www.lcm3b.uhp-nancy.fr/cims/

[3] http://www.obs.univ-bpclermont.fr/ima/ and www.geo.vu.nl/users/ima-cnmmn/

[4] http://www.univie.ac.at/Mineralogie/EMU/

[5] DST (Dipartimento di Scienze della Terra) Univ. Firenze - crystal@cesit1.unifi.it

[6] DST Univ. Genova - lucchett@mbox.dipteris.unige.it

[7] DST Univ. Modena - brigatti@mail.unimo.it; vezzalini.giovanna@mail.unimo.it

[8] Ist. di Geoscienze e Georisorse CNR Pavia - www.igg.cnr.it/indexpavia_ita.htm

[9] DST Univ. Pisa - merlino@dst.unipi.it

[10] Dip. di Scienze Mineralogiche e Petrologiche Univ. Torino - http://www.dsmp.unito.it/

[11] DST Univ. Siena - mellini@unisi.it

[12]Dip. di Scienze Geologiche Univ. Roma Tre - mottana@uniroma3.it

[13]Dip. Geomineralogico Univ. Bari - scordari@lgxserve.ciseca.uniba.it

[14] DST Univ. Camerino - paris@camars.unicam.it

[15] DST Univ. Milano - artioli@iummix.terra.unimi.it

[16] DST Univ. Ferrara - alberto.alberti@unife.it

[17] DST Univ. Perugia - zanazzi@unipg.it

[18] Dip. di Mineralogia Univ. Padova - adg@epidote.dmp.unipd.it

[19] DST Univ. Roma La Sapienza - Adriana.Maras@uniroma1.it