Reference:
▪ Oberti, R., Boiocchi, M., Hawthorne, F.C., Ciriotti M.E. (2018): Ferro-tschermakite from the Ploumanac'h granitic complex, Brittany, France: mineral description. European Journal of Mineralogy, 30, 171–176.
Abstract:
The mineral description is provided for ferro-tschermakite, ideally A□BCa2C(Fe2+3Al2)T(Si6Al2)O22W(OH)2. The type specimen has been found in the dump of the B.G.P. (Bâtiment et Granit de Ploumanac'h) northern granite quarry, La Clarté, Perros-Guirec, Ploumanac'h granitic complex, Brittany, France. The empirical formula derived from electron microprobe analysis and single-crystal structure refinement is: A(Na0.29K0.08)Σ=0.37 B(Ca1.69Fe2+0.11Mn2+0.02Na0.18)Σ=2.00 C(Fe2+1.84Mg1.54Al1.33Fe3+0.24V3+0.01Ti0.04)Σ=5.00 T(Si6.15Al1.85)Σ=8.00 O22 W(OH1.94F0.06)Σ=2.00. Ferro-tschermakite is biaxial (-), with α = 1.666(2), β = 1.680(2), γ = 1.690(2) and 2V (meas.) = 84(1)º, 2V (calc.) = 79.8. The unit-cell parameters are a = 9.7598(6), b = 18.0220(11), c = 5.3299(3) Å, β = 104.826(1)°, V = 906.27 (9) Å3, Z = 2, space group C2/m. The strongest ten reflections in the X-ray powder pattern obtained from single-crystal data [d values (in Å), I, (hkl)] are: 8.359, 100, (110); 2.708, 84, (151); 3.098, 55, (310); 2.552, 43, (-202); 2.595, 41, (061); 2.330, 33, (-351); 2.159, 27, (261); 2.936, 27, (221); 3.338, 27, (131); 2.012, 24, (-402; 351).
▪ Oberti, R., Boiocchi, M., Hawthorne, F.C., Ciriotti M.E. (2018): Ferro-tschermakite from the Ploumanac'h granitic complex, Brittany, France: mineral description. European Journal of Mineralogy, 30, 171–176.
Abstract:
The mineral description is provided for ferro-tschermakite, ideally A□BCa2C(Fe2+3Al2)T(Si6Al2)O22W(OH)2. The type specimen has been found in the dump of the B.G.P. (Bâtiment et Granit de Ploumanac'h) northern granite quarry, La Clarté, Perros-Guirec, Ploumanac'h granitic complex, Brittany, France. The empirical formula derived from electron microprobe analysis and single-crystal structure refinement is: A(Na0.29K0.08)Σ=0.37 B(Ca1.69Fe2+0.11Mn2+0.02Na0.18)Σ=2.00 C(Fe2+1.84Mg1.54Al1.33Fe3+0.24V3+0.01Ti0.04)Σ=5.00 T(Si6.15Al1.85)Σ=8.00 O22 W(OH1.94F0.06)Σ=2.00. Ferro-tschermakite is biaxial (-), with α = 1.666(2), β = 1.680(2), γ = 1.690(2) and 2V (meas.) = 84(1)º, 2V (calc.) = 79.8. The unit-cell parameters are a = 9.7598(6), b = 18.0220(11), c = 5.3299(3) Å, β = 104.826(1)°, V = 906.27 (9) Å3, Z = 2, space group C2/m. The strongest ten reflections in the X-ray powder pattern obtained from single-crystal data [d values (in Å), I, (hkl)] are: 8.359, 100, (110); 2.708, 84, (151); 3.098, 55, (310); 2.552, 43, (-202); 2.595, 41, (061); 2.330, 33, (-351); 2.159, 27, (261); 2.936, 27, (221); 3.338, 27, (131); 2.012, 24, (-402; 351).