Summary
The new mineral bellbergite, (K, Ba, Sr)2Sr2Ca2(Ca, Na)4Al18Si18O72 · 30H2O, has been found in Ca-rich xenoliths at the Bellberg volcano near Mayen, Eifel, Germany. It occurs as well formed bipyramids with a length up to 0.3 mm. Possible space groups are P63/mmc, P62c and P63mc with a = 13.244(1) Å, c = 15.988(2) Å, V = 2429 Å3, Z = 1. The density is: Dm, = 2.20(2) Mg/m3, Dc = 2.19 Mg/m3. The empirical formula based on 72 oxygen atoms is: Ba0.26Na0.72K1.33Sr2.36Ca5.32Al17.55Si18.36O72 · 30H2O. The mineral is uniaxial negative with ω = 1.522(2) and ε = 1.507(2) (λ = 589 nm). The strongest lines in the X-ray powder pattern are (d (Å), I, hkl): 3.80 (100) (300, 212, 104), 6.58 (80) (102), 2.95 (70) (312, 214), 2.21 (70) (330), 2.70 (50) (402), 2.50 (50) (410, 314), 1.83 (50) (416). The crystal structure corresponds to the zeolite structure type EAB.
Zusammenfassung
Das neue Mineral Bellbergit, (K, Ba, Sr)2Sr2Ca2(Ca, Na)4AlP18OPub72· 30H2O, wurde in Ca-reichen Xenolithen am Bellberg bei Mayen, Eifel, Deutschland gefunden. Es kommt als gut ausgebildete hexagonale Dipyramiden mit einer Länge von bis zu 0.3 mm vor. Mögliche Raumgruppen sind P63/mcc, P62c und P63mc mit a = 13.244(1) Å, c = 15.988(2) Å, V = 2429 Å3 und Z = 1. Die Dichte beträgt Dm = 2.20(2) Mg/m3, Dc = 2.19 Mg/m3. Die chemische Formel basierend auf 72 Sauerstoffatomen lautet: Ba0.26Na0.72K1.33Sr2.36Ca5.32Al17.55Si18.36O72 · 30H2O. Das Mineral ist einachsig negativ mit ω = 1.522(2) und ε = 1.507(2) (λ = 589nm). Die stärksten Linien des Pulverdiagramms liegen bei (d(Å), I, hkl): 3.80 (100) (300, 212,104), 6.58 (80) (102), 2.95 (70) (312, 214), 2.21 (70) (330), 2.70 (50) (402), 2.50 (50) (410, 314), 1.83 (50) (416). Die Kristallstruktur entspricht dem Zeolith-Strukturtyp EAB.
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Rüdinger, B., Tillmanns, E. & Hentschel, G. Bellbergite—a new mineral with the zeolite structure type EAB. Mineralogy and Petrology 48, 147–152 (1993). https://doi.org/10.1007/BF01163093
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DOI: https://doi.org/10.1007/BF01163093