Betzite, Na (sub 6) Ca (sub 2) (Al (sub 6) Si (sub 6) O (sub 24) )C (sub l4) , a new cancrinite-group mineral from the Eifel paleovolcanic region, Germany

Betzite, ideally Na (sub 6) Ca (sub 2) (Al (sub 6) Si (sub 6) O (sub 24) )C (sub l4) , a new cancrinite-group mineral, was discovered in a metasomatically altered (pyrometamorphosed) calcic xenolith, hosted by alkaline basalt at the Bellerberg paleovolcano in the Eastern Eifel region, Rhineland-Palatinate, Germany. The associated minerals are anorthite, phlogopite, diopside, grossular, fluorite, calcite, a tobermorite-like mineral, and vanadoallanite-(Ce). Betzite occurs as colorless hexagonal prismatic crystals up to 2 mm long and up to 0.5 mm thick. The new mineral is brittle, with a Mohs' hardness of 5-1/2. Distinct cleavage on {1010} and parting on {0001} are observed. The D (sub meas) = 2.38(2) g/cm (super 3) and D (sub calc) = 2.363 g/cm (super 3) . Betzite is optically uniaxial (+) with omega = 1.528(2) and epsilon = 1.545(3). The IR spectrum is given. The chemical composition of betzite is (wt.%; electron microprobe, H (sub 2) O determined by the modified Penfield method): Na (sub 2) O 11.88, K (sub 2) O 4.82, CaO 10.74, MgO 0.21, A (sub l2) O (sub 3) 27.32, Fe (sub 2) O (sub 3) 0.68, SiO (sub 2) 32.84, SO (sub 3) 1.89, Cl 10.48, H (sub 2) O 1.10, -O identical with Cl -2.37, total 99.59. The empirical formula is Na (sub 4.22) K (sub 1.13) Ca (sub 2.11) Mg (sub 0.06) (Si (sub 6.01) Al (sub 5.90) Fe (super 3+) (sub 0.09) O (sub 24) )Cl (sub 3.2 5) (SO (sub 4) )0.2 (sub 6) (H (sub 1.34) O (sub 0.64) ). The crystal structure was determined using single-crystal X-ray diffraction data. It is hexagonal, space group P6 (sub 3) , a = 12.8166(9) Aa, c = 5.3562(3) Aa, V = 761.95(12) Aa (super 3) 3 (at a temperature of 100 K) and Z = 3. Betzite is a dimorph of quadridavyne, with a disordered distribution of extra-framework components occupying channels. The strongest lines of the powder X-ray diffraction pattern [d, Aa (I, %) (hkl)] are: 11.14 (31) (100), 4.833 (93) (101), 3.715 (95) (300), 3.313 (100) (211), 2.787 (37) (400), 2.681 (56) (002, 131), 2.474 (35) (112, 401), 2.146 (24) (330). The mineral is named in honor of the German amateur mineralogist Volker Betz (b. 1947).