Aksenov, S.M. & Chukanov, N.V.: The crystal structure of a fluorine-dominant titanium calcium amphibole from the Eifel paleovolcanic area, Germany. Zeitschrift für Kristallographie - Crystalline Materials (Ahead of print)
A new fluorine-dominant titanium calcium amphibole (FTCA) was found in alkali basalts of the Rothenberg volcano situated in the Eifel paleovolcanic region, Rhineland-Palatinate (Rheinland-Pfalz), Germany. The empirical formula based on 24 (O+F) atoms is (Na0.65K0.30)(Ca1.95Na0.05)(Mg3.36Fe3+0.87Fe2+0.13Ti0.60)(Si5.92Al2.08)O22(F1.11O0.89). The crystal structure has been studied based on single-crystal X-ray diffraction data. The monoclinic unit-cell parameters are: a=9.8684(2) Å, b=18.0457(3) Å, c=5.3113(1) Å, β=105.543(3)°; space group C2/m. The structure was refined to R=3.39% in anisotropic approximation using 3661F>4σF. The studied mineral is the first representative of F-dominant amphiboles with CTi>0.5. It is considered as a F-dominant analogue of ferri-kaersutite NaCa2[Mg3Fe3+Ti](Si6Al2O22)O2.
A new fluorine-dominant titanium calcium amphibole (FTCA) was found in alkali basalts of the Rothenberg volcano situated in the Eifel paleovolcanic region, Rhineland-Palatinate (Rheinland-Pfalz), Germany. The empirical formula based on 24 (O+F) atoms is (Na0.65K0.30)(Ca1.95Na0.05)(Mg3.36Fe3+0.87Fe2+0.13Ti0.60)(Si5.92Al2.08)O22(F1.11O0.89). The crystal structure has been studied based on single-crystal X-ray diffraction data. The monoclinic unit-cell parameters are: a=9.8684(2) Å, b=18.0457(3) Å, c=5.3113(1) Å, β=105.543(3)°; space group C2/m. The structure was refined to R=3.39% in anisotropic approximation using 3661F>4σF. The studied mineral is the first representative of F-dominant amphiboles with CTi>0.5. It is considered as a F-dominant analogue of ferri-kaersutite NaCa2[Mg3Fe3+Ti](Si6Al2O22)O2.