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Mineralogical ClassificationIMA 2005-018 = Poppiite: description-type

7th Apr 2006 18:16 UTCMarco E. Ciriotti Manager

Reference:

• Brigatti, M.F., Caprilli, E., Marchesini, M. (2006): Poppiite, the V3+ end member of the pumpellyite group: Description and crystal structure. American Mineralogist, 91, 584-588.


Abstract:

Poppiite, a new mineral from Gambatesa mine (Val Graveglia, Genova, Northern Italy), is the V3+ end-member of the pumpellyite group <(Ca7.68 Na0.27 K0.03 Rb0.02)8.00(V3+1.26 Fe3+1.02 Mg0.78 Mn2+0.59 Al0.31 Cu2+ 0.04)4.00 (V3+ 6.89 Al1.07 Ti0.04)8.00 (Si11.69Al0.31)12.00 O42 (OH)14; C2/m, a = 19.2889(6), b = 6.0444(2), c = 8.8783(3) Å, ß = 97.328(2)°, V = 1026.66(6) Å3, Dmeas = 3.36(2) g/cm3, and Dcalc = 3.44 g/cm3>. Poppiite crystals, with size varying from 0.1 to 0.6 mm, are minute, greenish-brown, and prismatic, and are associated with roscoelite, ganophyllite, manganaxinite, goldmanite, and calcite.

The strongest lines in the X-ray powder diffraction pattern are: 2.930, 100, (511); 3.817, 70, (202); 2.548, 65, (13); 2.551, 62, (420); 1.612, 57, (31,424); and 2.367, 51, (222, 403). Poppiite is optically negative, with 2Vcalc = 44°, n = 1.768(9), nß 1.804(8), n 1.810(9). The pleochroic scheme is = light yellowish brown, ß = deep greenish brown, and = brown to reddish brown. The crystal structure was refined using 1918 unique reflections to R = 0.0307. Like the other pumpellyite-group minerals the crystal structure of poppiite consists of chains of edge-sharing octahedra linked by SiO4, Si2O7, and CaO7 polyhedra.

7th Apr 2006 20:44 UTCMarco E. Ciriotti Manager

Important propedeutic references for poppiite are:


• Caprilli, E. (2004): Miche e cloriti: implicazioni cristallochimiche, PhD thesis, University of Modena and Reggio Emilia, 205 pp.


• Caprilli, E. (2005): Micas and chlorites: crystal chemical implications. Plinius, 31, 65-70.

9th Apr 2006 14:32 UTCPeter Haas

All added.
 
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