Titre du document / Document title

Rosenbergite, AlF[F_0.5(H₂O)_0.5]₄.H₂O, a new mineral from the Cetine mine (Tuscany, Italy): description and crystal structure

Auteur(s) / Author(s)

OLMI F. ⁽¹⁾ ; SABELLI C. ⁽¹⁾ ; TROSTI-FERRONI R. ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

⁽¹⁾ CNR, cent. studio minerogenesi geochimica applicata, 50121 Firenze, ITALIE

Résumé / Abstract

Rosenbergite is a new aluminium fluoride mineral from the Cetine mine, Tuscany, Italy. It occurs as radiating tufts of slender tetragronal crystals, elongated parallel to [001], in cavities in a highly silicified limestone. The crystals are colourless and transparent, with a vitreous lustre. Associated minerals are gypsum, fluorite, elpasolite, ralstonite and onoratoite. Electron microprobe analysis (water by difference) grives Al_1.02F_2.982.99H₂O (simplified formula AlF₃.3H₂O). Optically uniaxial (-) with ε = 1.403 and ω = 1.427; VHN₁₅ microhardness 103; d_calc = 2.111 g/cm³; d_meas = 2.10(1) g/cm³. The unit cell is tetragronal a = 7.715(1), c = 3.648(1)Å, space group P4/n and Z = 2. The strongest lines in the X-ray Gandolfi pattern are (d_obs,I,hkl 5.47(100)(100), 2.439(72)(130), 2.027(70)(131), 1.775(78)(012), 1.725(85)(240), 1.306(70)(142). The IR spectrum is also griven. The mineral is named for P.E. Rosenberg of Washington State University, U.S.A. The crystal structure was refined to an R index of 0.0186, using a set of 245 observed (16 σ) reflections (R = 0.0276 for all 316 collected reflections). The structure consists of chains of comer-linked Al[F₄(H₂O)₂] octahedra running parallel to [001] and isolated water molecules. A dense network of hydrogren bonds strongly connects the Al-F chains. The structural formula is AlF[F_0.5(H₂O)_0.5]₄.H₂O

Revue / Journal Title

European journal of mineralogy   ISSN 0935-1221 

Source / Source

1993, vol. 5, n^o6, pp. 1167-1173 (16 ref.)

Langue / Language

Anglais

Editeur / Publisher

Schweizerbart, Stuttgart, ALLEMAGNE  (1989) (Revue)

Mots-clés anglais / English Keywords

new minerals ; fluorides ; Tuscany ; crystal structure ; crystal form ; silicification ; limestone ; color ; paragenesis ; electron probe data ; structural formula ; optical properties ; hardness ; density ; unit cell ; cell dimensions ; space groups ; X-ray diffraction analysis ; infrared spectra ; atomic packing ; coordination ; bonding ; X-ray powder diffraction ; SEM data ; Italy ; Europe ; carbonate rocks ; sedimentary rocks ;

Mots-clés français / French Keywords

Minéral nouveau ; Fluorure ; Toscane ; Structure cristalline ; Forme cristalline ; Silicification ; Calcaire ; Couleur ; Paragenèse ; Donnée microsonde électronique ; Formule structurale ; Propriété optique ; Dureté ; Densité ; Maille élémentaire ; Constante réticulaire ; Groupe espace ; Diffraction RX ; spectre IR ; Empilement atome ; Coordinence ; Liaison interatomique ; Diagramme poudre ; Donnée MEB ; Mine Cetine ; Rosenbergite ; Anisotropie thermique ; Italie ; Europe ; Roche carbonatée ; Roche sédimentaire ;

Mots-clés espagnols / Spanish Keywords

Mineral nuevo ; Fluoruro ; Toscana ; Estructura cristalina ; Forma cristalina ; Silicificación ; Calcáreo ; Color ; Paragénesis ; Dato sonda electrónica ; Propiedad óptica ; Dureza ; Densidad ; Celdilla cristalina ; Constante reticular ; Grupo espacio ; Difracción RX ; Espectro IR ; Estructura átomo ; Coordinancia ; Enlace interatómico ; Diagrama polvo ; Dato MEB ; Italia ; Europa ; Roca carbonatada ; Roca sedimentaria ;

Localisation / Location

INIST-CNRS, Cote INIST : 519, 35400002596709.0150