Reference:
▪ Chukanov, N.V., Zubkova, N.V., Blass, G., Pekov, I.V., Varlamov, D.A., Belakovskiy, D.I., Ksenofontov, D.A., Britvin, S.N., Pushcharovsky, D.Yu. (2019): Kruijenite, Ca4Al4(SO4)F2(OH)16·2H2O, a new mineral with microporous structure from the Eifel paleovolcanic region, Germany. Mineralogy and Petrology, 113, 229–236.
Abstract:
The new mineral kruijenite, ideally Ca4Al4(SO4)F2(OH)16·2H2O, was found in a calcic xenolith from tephra of the Feuerberg paleovolcano situated near Daun, Eifel paleovolcanic region, Rhineland-Palatinate, Germany. It is associated with fluorite, calcite, aragonite, cuspidine, magnesioferrite, hematite, sharyginite, harmunite, and an insufficiently investigated hydrous Ca-Mg-Al silicate. Kruijenite occurs as pale greenish-yellow to colourless long prismatic tetragonal crystals up to 0.1 mm × 1 mm in cavities typically combined in radiating or random aggregates. The mineral is brittle, with Mohs’ hardness of 3; Dcalc is 2.573 g/cm3. The IR spectrum is given. Kruijenite is optically uniaxial (−), ω = 1.576(3), ε = 1.561(3). The chemical composition (wavelength dispersive spectrometer Oxford INCA Wave 700 EPMA analyser, H2O calculated from structural data) is: CaO 32.38 wt%, Al2O3 27.75 wt%, Cr2O3 1.45 wt%, SO3 8.09 wt%, F 5.84 wt%, H2O 25.64 wt%, –O=F –2.46 wt%, total 98.69 wt%. The empirical formula is Ca4.00(Al3.77Cr0.13)Σ3.90(SO4)0.70F2.13(OH)16.17·1.79H2O (Z = 2). Kruijenite is tetragonal, space group P4/ncc, a = 12.9299(4) Å, c = 5.2791(3) Å, V = 882.57(6) Å3, Z = 2. The crystal structure was solved and refined to R = 0.121. Kruijenite represents a novel structure type. Its structure is based on the microporous pseudo-framework built by Al(OH)6 octahedra and CaF2(OH)6 polyhedra. The strongest reflections of the powder X-ray diffraction pattern [d (I) (hkl)] are: 9.12 Å (77%) (110), 4.565 Å (100%) (220), 4.084 Å (50%) (310), 2.964 Å (74%) (321), 2.694 Å (27%) (411), 2.321 Å (24%) (431), 2.284 Å (29%) (511), 2.217 Å (22%) (321, 530), 1.971 Å (40%) (611). The mineral is named in honor of the Dutch collector of Eifel minerals Fred Kruijen (born in 1956).
▪ Chukanov, N.V., Zubkova, N.V., Blass, G., Pekov, I.V., Varlamov, D.A., Belakovskiy, D.I., Ksenofontov, D.A., Britvin, S.N., Pushcharovsky, D.Yu. (2019): Kruijenite, Ca4Al4(SO4)F2(OH)16·2H2O, a new mineral with microporous structure from the Eifel paleovolcanic region, Germany. Mineralogy and Petrology, 113, 229–236.
Abstract:
The new mineral kruijenite, ideally Ca4Al4(SO4)F2(OH)16·2H2O, was found in a calcic xenolith from tephra of the Feuerberg paleovolcano situated near Daun, Eifel paleovolcanic region, Rhineland-Palatinate, Germany. It is associated with fluorite, calcite, aragonite, cuspidine, magnesioferrite, hematite, sharyginite, harmunite, and an insufficiently investigated hydrous Ca-Mg-Al silicate. Kruijenite occurs as pale greenish-yellow to colourless long prismatic tetragonal crystals up to 0.1 mm × 1 mm in cavities typically combined in radiating or random aggregates. The mineral is brittle, with Mohs’ hardness of 3; Dcalc is 2.573 g/cm3. The IR spectrum is given. Kruijenite is optically uniaxial (−), ω = 1.576(3), ε = 1.561(3). The chemical composition (wavelength dispersive spectrometer Oxford INCA Wave 700 EPMA analyser, H2O calculated from structural data) is: CaO 32.38 wt%, Al2O3 27.75 wt%, Cr2O3 1.45 wt%, SO3 8.09 wt%, F 5.84 wt%, H2O 25.64 wt%, –O=F –2.46 wt%, total 98.69 wt%. The empirical formula is Ca4.00(Al3.77Cr0.13)Σ3.90(SO4)0.70F2.13(OH)16.17·1.79H2O (Z = 2). Kruijenite is tetragonal, space group P4/ncc, a = 12.9299(4) Å, c = 5.2791(3) Å, V = 882.57(6) Å3, Z = 2. The crystal structure was solved and refined to R = 0.121. Kruijenite represents a novel structure type. Its structure is based on the microporous pseudo-framework built by Al(OH)6 octahedra and CaF2(OH)6 polyhedra. The strongest reflections of the powder X-ray diffraction pattern [d (I) (hkl)] are: 9.12 Å (77%) (110), 4.565 Å (100%) (220), 4.084 Å (50%) (310), 2.964 Å (74%) (321), 2.694 Å (27%) (411), 2.321 Å (24%) (431), 2.284 Å (29%) (511), 2.217 Å (22%) (321, 530), 1.971 Å (40%) (611). The mineral is named in honor of the Dutch collector of Eifel minerals Fred Kruijen (born in 1956).