Referenza:
▪ Chukanov, N.V., Rastsvetaeva, R.K., Aksenov, D.M., Blass, G., Pekov, I.V., Belakovskiy, D.I., Tschörtner, J., Schüller, W., Ternes, B. (2014) Emmerichite, Ва2Na(Na,Fe2+)2(Fe3+,Mg)Ti2(Si2O7)2O2F2, a new lamprophyllite-group mineral from the Eifel volcanic region, Germany. New Data on Minerals, 49, 5–13.
Abstract (from American Mineralogist):
Emmerichite (IMA 2013-064), with ideal formula Ва2Na3Fe3+Ti2(Si2O7)2O2F2, is a new mineral found in alkaline basalts at the mountain Rother Kopf, near Gerolstein, Eifel Mountains (Rheinland-Pfalz, Germany). Associated minerals are the high-temperature pneumatolitic (partly altered in late hydrothermal processes) minerals: nepheline, leucite, augite, phlogopite, fluorapatite, götzenite, åkermanite, günterblassite, magnetite, and perovskite. It is found as lamellar (often plank-like) crystals up to 0.05 × 0.3 × 0.5 mm and clusters up to 1 mm across. The mineral is brown and vitreous with a white streak. It is brittle, the Mohs hardness is 3–4; cleavage is perfect on {100}. Dcalc = 3.864 g/cm3. Optically emmerichite is biaxial (+) with α = 1.725(4), β = 1.728(4), γ = 1.759(4), 2Vmeas = 80(5)°, 2Vcalc = 79° (589 nm). Dispersion is r > v, medium; X = a; Y and Z parallel to (100), Y is parallel to the elongation of the crystals. Pleochroism is moderate: Z (brown) ≥ Y (light brown) > X (greenish gray). The mineral shows no fluorescence in the UV wavelength range. IR spectrum shows the absence of O–H bonds and the following band assignments: (cm−1, s = strong, w = weak, and sh = shoulder): 1055sh, 1038s, 954s, 907s, 853s (Si–O stretching vibrations), 686w, 658w (O–Si–O bending vibrations of Si2O7 groups), 580sh, 536 (combinations of stretching vibrations of TiO and Fe3+O6 polyhedra), and 458s, 400s (combinations of Si–O–Si bending vibrations and stretching vibrations of MO6, octahedra). The average of 5 electron probe WDS analyses is [wt% (range)]: Na2O 5.44 (5.20–5.78), K2O 1.03 (0.95–1.13), CaO 1.98 (1.86–2.07), SrO 3.23 (3.02–3.48), BaO 25.94 (25.50–26.23), MgO 3.13 (3.05–3.28), MnO 2.22 (2.04–2.43), FeO total 10.91 (10.75–11.16) [FeO 4.85 and Fe2O3 6.73 (from structural refinement)], TiO2 15.21 (15.05–15.45), ZrO2 0.52 (0.33–0.78), Nb2O5 1.32 (1.04–1.53), SiO2 27.13 (26.92–27.38), F 3.54 (3.35–3.74), –O=F2 1.49, total 100.78. The empirical formula calculated on the basis of 18 (O+F) pfu is: Embedded Image . The strongest X-ray powder diffraction (Gandolfi method) lines [d Å (I%; hkl)] are: 9.97 (55; 200), 3.461 (65; 510,311,401), 3.312 (40; 220,600), 2.882 (38; Embedded Image ,420), 2.792 (100; 221,511), 2.670 (56; 002,601, Embedded Image ), 2.629 (45; 710, Embedded Image ), 2.140 (57; 131,022,621, Embedded Image ). The X-ray powder diffraction pattern was indexed in monoclinic unit cell with a = 19.93(3), b = 7.11(1), c = 5.407(8) Å, β = 96.5(1)°, V = 760 Å3. X-ray single-crystal diffraction study [refined to R1 = 0.0457 for 4400 unique Fo > 4σ(F) reflections] on a crystal fragment 220 × 200 × 50 μm shows the mineral is monoclinic, space group C2/m, Z = 2. Emmerichite structure is similar to lamprophyllite (Sr,Na)Na3Ti3(Si2O7)2O2(OH)2. It is based on HOH modules: the O sheet contains large M1 and M2 octahedra, occupied dominantly by Na, and the M3 octahedron, which is occupied dominantly by Fe3+ (+Mg), being the distinct feature of emmerichite; the H sheets are built by [Si2O7] groups and titanium in fivefold coordination. According to Sokolova (2006) the linkage of O and H sheets is linkage 1 where two [Si2O7] groups link to the trans edges of the same octahedron of the O sheet. Large cations (Ba, Sr, K) fill the interlayer space between adjacent HOH-modules. The holotype of emmerichite is deposited in the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow.
▪ Chukanov, N.V., Rastsvetaeva, R.K., Aksenov, D.M., Blass, G., Pekov, I.V., Belakovskiy, D.I., Tschörtner, J., Schüller, W., Ternes, B. (2014) Emmerichite, Ва2Na(Na,Fe2+)2(Fe3+,Mg)Ti2(Si2O7)2O2F2, a new lamprophyllite-group mineral from the Eifel volcanic region, Germany. New Data on Minerals, 49, 5–13.
Abstract (from American Mineralogist):
Emmerichite (IMA 2013-064), with ideal formula Ва2Na3Fe3+Ti2(Si2O7)2O2F2, is a new mineral found in alkaline basalts at the mountain Rother Kopf, near Gerolstein, Eifel Mountains (Rheinland-Pfalz, Germany). Associated minerals are the high-temperature pneumatolitic (partly altered in late hydrothermal processes) minerals: nepheline, leucite, augite, phlogopite, fluorapatite, götzenite, åkermanite, günterblassite, magnetite, and perovskite. It is found as lamellar (often plank-like) crystals up to 0.05 × 0.3 × 0.5 mm and clusters up to 1 mm across. The mineral is brown and vitreous with a white streak. It is brittle, the Mohs hardness is 3–4; cleavage is perfect on {100}. Dcalc = 3.864 g/cm3. Optically emmerichite is biaxial (+) with α = 1.725(4), β = 1.728(4), γ = 1.759(4), 2Vmeas = 80(5)°, 2Vcalc = 79° (589 nm). Dispersion is r > v, medium; X = a; Y and Z parallel to (100), Y is parallel to the elongation of the crystals. Pleochroism is moderate: Z (brown) ≥ Y (light brown) > X (greenish gray). The mineral shows no fluorescence in the UV wavelength range. IR spectrum shows the absence of O–H bonds and the following band assignments: (cm−1, s = strong, w = weak, and sh = shoulder): 1055sh, 1038s, 954s, 907s, 853s (Si–O stretching vibrations), 686w, 658w (O–Si–O bending vibrations of Si2O7 groups), 580sh, 536 (combinations of stretching vibrations of TiO and Fe3+O6 polyhedra), and 458s, 400s (combinations of Si–O–Si bending vibrations and stretching vibrations of MO6, octahedra). The average of 5 electron probe WDS analyses is [wt% (range)]: Na2O 5.44 (5.20–5.78), K2O 1.03 (0.95–1.13), CaO 1.98 (1.86–2.07), SrO 3.23 (3.02–3.48), BaO 25.94 (25.50–26.23), MgO 3.13 (3.05–3.28), MnO 2.22 (2.04–2.43), FeO total 10.91 (10.75–11.16) [FeO 4.85 and Fe2O3 6.73 (from structural refinement)], TiO2 15.21 (15.05–15.45), ZrO2 0.52 (0.33–0.78), Nb2O5 1.32 (1.04–1.53), SiO2 27.13 (26.92–27.38), F 3.54 (3.35–3.74), –O=F2 1.49, total 100.78. The empirical formula calculated on the basis of 18 (O+F) pfu is: Embedded Image . The strongest X-ray powder diffraction (Gandolfi method) lines [d Å (I%; hkl)] are: 9.97 (55; 200), 3.461 (65; 510,311,401), 3.312 (40; 220,600), 2.882 (38; Embedded Image ,420), 2.792 (100; 221,511), 2.670 (56; 002,601, Embedded Image ), 2.629 (45; 710, Embedded Image ), 2.140 (57; 131,022,621, Embedded Image ). The X-ray powder diffraction pattern was indexed in monoclinic unit cell with a = 19.93(3), b = 7.11(1), c = 5.407(8) Å, β = 96.5(1)°, V = 760 Å3. X-ray single-crystal diffraction study [refined to R1 = 0.0457 for 4400 unique Fo > 4σ(F) reflections] on a crystal fragment 220 × 200 × 50 μm shows the mineral is monoclinic, space group C2/m, Z = 2. Emmerichite structure is similar to lamprophyllite (Sr,Na)Na3Ti3(Si2O7)2O2(OH)2. It is based on HOH modules: the O sheet contains large M1 and M2 octahedra, occupied dominantly by Na, and the M3 octahedron, which is occupied dominantly by Fe3+ (+Mg), being the distinct feature of emmerichite; the H sheets are built by [Si2O7] groups and titanium in fivefold coordination. According to Sokolova (2006) the linkage of O and H sheets is linkage 1 where two [Si2O7] groups link to the trans edges of the same octahedron of the O sheet. Large cations (Ba, Sr, K) fill the interlayer space between adjacent HOH-modules. The holotype of emmerichite is deposited in the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow.