Fehér, Balázs

Szakáll, Sándor

Vezzalini, G.

English

Szakáll Sándor

Fehér Balázs

Vezzalini G.

University of Szeged

Acta Mineralogica-Petrographica, Abstract Series 5, Szeged, 2006 www.sci.u-szeged.hu/asvanytan/acta.htm 113OCCURRENCE OF COWLESITE IN ANDESITE AT PILISSZENTLÁSZLÓ, PILIS MTS., HUNGARY  SZAKÁLL, S.,1 FEHÉR, B.2 & VEZZALINI, G.3 1 Department of Mineralogy and Petrology, University of Miskolc, H-3515 Miskolc-Egyetemváros, Hungary E-mail: askszs@gold.uni-miskolc.hu 2 Department of Mineralogy, Herman Ottó Museum, Kossuth u. 13, H-3525 Miskolc, Hungary 3 Dipartimento di Scienze della Terra, Università di Modena, via S. Eufemia 19, I-41100 Modena, Italy   Cowlesite was first described by WISE & TSCHERNICH (1975) from seven different localities from the U.S.A. All known occurrences are in basic lavas. VEZZALINI et al. (1992) mentioned some localities of cowlesite in basalt from Northern Ireland. It was unknown in the Carpathian region to date.  There are a few zeolite occurrences in cavities and fis-sures of andesite in the Pilis Mts. (NNW from Budapest). Usual zeolite associations in this territory include stilbite, chabazite and heulandite. However, near Pilisszentlászló (in the Pálbükk quarry) white, soft, spherical aggregates have very rarely been found in the cavities of the rocks. They con-sist of very thin radiating plates with pearly lustre. The di-ameter of the spherules reaches up to 0.5 mm. These spher-ules are cowlesite according to XRD patterns and electron-microprobe analyses. Cowlesite is often covered by thin smectite (saponite?) and/or goethite films. In the cavities some relatively high temperature rock-forming minerals occur in the form of well-developed, but tiny crystals (e.g. plagioclase, amphibole, apatite, magnetite, hematite, and rarely cheralite–monazite). These earlier formed minerals are followed by cowlesite, chabazite, smectites, goethite, hema-tite and calcite. Cowlesite is a zeolite with unknown structure. Complete single crystal X-ray study has not been performed so far because cowlesite crystals are always very small (up to 0.1 mm in width) and thin (up to 2 µm). According to X-ray powder data and very faint precession photographs, cowlesite is orthorhombic; this symmetry corresponds to the results of the optical studies (GOTTARDI & GALLI, 1985). Because of the very limited quantity of available material from the cowlesite from Pilisszentlászló, experimental XRPD pattern was obtained by a 114.6 mm Gandolfi camera using CoKα radiation. Observed reflections on the X-ray film are [d in Å (intensity, hkl)]: 15.15 (vs, 010), 12.44 (w, 001), 8.46 (w, 101), 7.64 (vw, 020), 5.68 (w, 121), 4.16 (vw, 202), 3.80 (w, 040), 3.45 (vw, 141), 3.27 (vw, 321), 3.12 (w, 004), 3.06 (vw, 050), 2.953 (vw, 051), 2.826 (w, 043), and 2.225 (vw, 352). Unit cell data calculated from the powder pattern are a = 11.46(6) Å, b = 15.19(3) Å, c = 12.45(3) Å, V = 2166(12) Å3. Electron-microprobe analyses (sample G145) were car-ried out in the wavelength-dispersive mode. The results are very close to those published earlier (WISE & TSCHERNICH, 1975; VEZZALINI et al., 1992). The data (Table 1) correspond to a composition close to the stoichiometric formula for cowlesite (CaAl2Si3O10 • 6H2O) and indicate a relatively narrow compositional range. H2O could not be directly determined due to the paucity of the sample.   References GOTTARDI, G. & GALLI, E. (1985): Natural zeolites. Ber-lin: Springer-Verlag. VEZZALINI, G., ARTIOLI, G., QUARTIERI, S. & FOY, H. (1992): Mineralogical Magazine, 56: 575–579. WISE, W.S. & TSCHERNICH, R.W. (1975): American Mineralogist, 60: 951–956.  Table 1: Chemical composition (in wt%) according to electron-microprobe analyses and corresponding structural formulae for cowlesite from Pilisszentlászló (H2O was calculated from difference)  No. BaO FeO SrO K2O CaO SiO2 Na2O MgO Al2O3 Total 1 0.00 0.00 0.05 0.02 11.95 40.99 0.69 0.10 21.67 75.47 2 0.04 0.02 0.00 0.02 11.15 39.33 0.65 0.09 20.25 71.55 3 0.05 0.07 0.08 0.09 11.85 41.24 0.92 0.15 22.36 76.81 4 0.01 0.10 0.01 0.08 11.40 43.59 0.99 0.13 24.77 81.08 5 0.00 0.06 0.06 0.04 12.17 41.21 0.82 0.14 22.47 76.97 6 0.00 0.07 0.01 0.08 11.21 40.21 0.76 0.10 19.88 72.32 7 0.00 0.05 0.00 0.08 11.41 46.04 0.94 0.12 25.24 83.88  1) (Ca0.96 Na0.10 Mg0.01)Σ=1.07 [Al1.91 Si3.06 O10] • 6.11H2O 2) (Ca0.94 Na0.10 Mg0.01)Σ=1.05 [Al1.88 Si3.09 O10] • 7.45H2O 3) (Ca0.93 Na0.13 Mg0.02 K0.01)Σ=1.09 [Al1.94 Si3.03 O10] • 5.68H2O 4) (Ca0.85 Na0.13 Mg0.01 Fe0.01 K0.01)Σ=1.01 [Al2.02 Si3.02 O10] • 4.37H2O 5) (Ca0.96 Na0.12 Mg0.02)Σ=1.10 [Al1.94 Si3.02 O10] • 5.63H2O 6) (Ca0.93 Na0.11 Mg0.01 K0.01)Σ=1.06 [Al1.82 Si3.13 O10] • 7.19H2O 7) (Ca0.81 Na0.12 Mg0.01 K0.01)Σ=0.95 [Al1.98 Si3.07 O10] • 3.58H2O brought to you by COREView metadata, citation and similar papers at core.ac.ukprovided by University of Szeged

Occurrence of cowlesite in andesite at Pilisszentlászló, Plis Mts., Hungary

http://acta.bibl.u-szeged.hu/31767/1/mineralogica_as_005_113.pdf

Occurrence of cowlesite in andesite at Pilisszentlászló, Plis Mts., Hungary

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