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American Mineralogist; June 1998; v. 83; no. 5-6; p. 607-617
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Tschortnerite, a copper-bearing zeolite from the Bellberg volcano, Eifel, Germany

H. Effenberger, G. Giester, W. Krause, and H. J. Bernhardt

Universitat Wien, Institut fur Mineralogie und Kristallographie, Vienna, Austria

The new mineral tschortnerite, ideally Ca 4 (K,Ca,Sr,Ba) 3 Cu 3 (OH) 8 [Si 12 Al 12 O 48 ].chi H 2 O, chi > or =20, occurs as well-formed cubes up to a maximum size of 0.15 mm in a Ca-rich xenolith at the Bellberg volcano near Mayen, Eifel, Germany. The light blue, transparent crystals are optically isotropic, n = 1.504(2). Microprobe analysis (in weight percent) gave CaO 13.10, CuO 9.64, SrO 4.49, BaO 1.93, K 2 O 1.37, Fe 2 O 3 0.30, Al 2 O 3 25.21, SiO 2 30.25, H 2 O (calc. by difference) 13.71. The empirical formula based on 48 O atoms within the tetrahedral net is Ca (sub 5.60) Sr (sub 1.04) K (sub 0.70) Ba (sub 0.30) Cu (sub 2.90) Fe (sub 0.09) Al (sub 11.85) Si (sub 12.06) O 48 (OH) (sub 8.44) .14.01H 2 O. Tschortnerite is cubic, space group Fm3m [a = 31.62(1) Aa, V = 31614 Aa3, Z = 16]. The density is D meas = 2.1 g/cm 3 , D calc = 2.10 g/cm 3 . Single-crystal X-ray investigations showed that tschortnerite is a zeolite; the structure contains interconnection of double six-rings, double eight-rings, sodalite cages, truncated cubo-octahedra, and previously unknown 96-membered cages (tschortnerite cage). A new structural unit is the [Cu 12 (OH) 24 ]Ca 8 O 24 (H 2 O) 8 cluster centered within the truncated cubo-octahedron. The cluster is formed by a rhombdodecahedron-like arrangement of corner connected CuO 4 squares, the eight CaO 7 polyhedra are branched. The sodalite cage houses Ca 4 (OH) 4 O 12 clusters of edge-sharing CaO 6 octahedra. Half-occupied (K,Ca,Sr,Ba) positions were located in the basal and top face of the double eight-rings, i.e., the border to the tschortnerite cage. Within the large tschortnerite cage only H 2 O molecules were localized.

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C. L. Lengauer, U. Kolitsch, and E. Tillmanns
Florkeite, K3Ca2Na[Al8Si8O32] {middle dot} 12H2O, a new phillipsite-type zeolite from the Bellerberg, East Eifel volcanic area, Germany
European Journal of Mineralogy, August 1, 2009; 21(4): 901 - 913.
[Abstract] [Full Text] [PDF]


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