Zeolitová mineralizace z Libé u Chebu (Česká republika)

Abstract

A new occurrence of zeolite mineralization with phillipsite-K, phillipsite-Ca, thomsonite-Ca, natrolite and gonnardite has been discovered in an active basalt quarry in the Libá village near Cheb (Czech Republic). Phillipsites in small cavities form druses of white or colourless crystals up to 1 mm in size. Chemical analyses of phillipsite-K correspond to the empirical formula (K1.85Na1.24Ca0.83Ba0.27Sr0.01)Σ4.20(Al6.28Si10.33O32)·12H2O and phillipsite-Ca to (Ca1.84K1.33Na0.14Ba0.06)Σ3.37(Al5.97Si10.20O32)·12H2O. The unit-cell parameters were refined from the powder X-ray data for phillipsite-Ca as: a 9.924(2), b 14.309(3), c 8.7414(14) Å, β 124.92(2)° and V 1017.8(5) Å3. Thomsonite-Ca forms transparent hemispheric radial aggregates up to 1 cm in size. Its unit-cell parameters refined from the powder X-ray data are a 13.105(5), b 13.857(5), c 13.247(6) Å and V 2266.7(6) Å3 and its chemical analyses correspond to the empirical formula Ca1.79Sr0.18Na1.05(Al4.81 Si5.15)O20·6H2O. Natrolite occurs as snow white hemispheric radial clusters. Its unit-cell parameters refined from the powder X-ray data are a 18.326(7), b 18.569(7), c 6.594(3) Å and V 2243.8(9) Å3 and empirical formula is Na1.60Ca0.05(Al2.08 Si3.02)O10·2H2O. Gonnardite forms colourless or white aggregates of flat acicular crystals up to 2 mm in size. Its unit-cell parameters refined from the powder X-ray data are a 13.221(8), c 6.6233(4) Å and V 1156.9 Å3 and empirical formula is (Na3.14Ca2.21Sr0.02)Σ5.37(Al8.92Si11.41)Σ20.33O40·12H2O.