Original paper
Potassic-aluminotaramite from Sierra de los Filabres, Spain
Oberti, Roberta; Boiocchi, Massimo; Smith, David C.; Medenbach, Olaf; Helmers, Henk
European Journal of Mineralogy Volume 20 Number 6 (2008), p. 1005 - 1010
published: Dec 15, 2008
Abstract
Potassic-aluminotaramite, ideally AK (CaNa) B(Fe2+3Al2) C(Si6Al2) O22 W(OH)2, has been found in a meta-monzonite rock sampled at Sierra de los Filabres, S.E. Spain; the paragenesis that contains the amphibole is mainly formed by feldspar, quartz, and clinopyroxene. This paper reports a complete mineral description and crystal-structure details for this new taramite end-member that has been recognised by IMA-CNMMC with the vote 2007-015. Holotype potassic-aluminotaramite has the experimental unit formula A(Na0.34K0.66)Σ1.00 B(Fe2+0.01 Na0.85 Ca1.14)Σ2.00 C(Fe2+2.80 Mg0.33 Al1.26 Fe3+ 0.46Ti0.05Mn0.10)TΣ5.00(Si6.01 Al1.99)Σ8.00 O22 W(OH1.96 F0.03 Cl0.01)Σ2.00; a = 9.8505(5), b = 18.0075(9), c = 5.3518(3) Å, β = 104.775(4), V = 917.9(2) Å3; Dcalc = 3.40 g/cm3. Optics: biaxial (-); α 1.686(1), β 1.703(3), γ 1.706(3) (λ = 589 nm). The ten strongest reflections in the X-ray powder pattern [d values (in Å), I, (hkl)] are: 8.420, 100, (110); 2.714, 75.03, (151); 2.565, 59.62, (-202); 3.127, 52.54, (310); 2.596, 49.03, (061); 3.400, 37.92, [(131) (041)]; 2.166, 33.71, [(261) (-332)]; 2.340, 32.38, (-351); 2.956, 24.79, (221); 2.297, 24.57, [(-171) (-312)].
Keywords
potassic-aluminotaramite • new mineral • amphibole • chemical analysis • crystal structure • spain