Abstract

Potassic-aluminotaramite, ideally AK (CaNa) B(Fe32+ Al2) C(Si6Al2) O22W(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)∑1.00B(Fe0.012+ Na0.85 Ca1.14)∑2.00C(Fe2.802+ Mg0.33 Al1.26 Fe0.463+ Ti0.05 Mn0.10)∑5.00T (Si6.01 Al1.99)∑8.00 O22W(OH1.96 F0.03 Cl0.01)∑2.00; 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)].

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