Zeofylit, tobermorit, fluorapofylit-(K) a doprovodná zeolitová mineralizace z Křížového vrchu u Cvikova v Lužických horách (Česká republika)

Abstract

Zeophyllite, tobermorite, kenotobermorite, fluorapophylite-(K) and associated zeolites were found in cavities of Cenozoic basaltic rocks of small abandoned quarry at western slope of the Křížový vrch hill (443 m a.s.l.), 1.5 km NE from Cvikov, 13 km NNE from Česká Lípa, Lužické hory Mountains, Czech Republic. Zeophyllite forms colorless spherical aggregates with pearly lustre usually 3 - 4 mm in size, aggregates with diameter up to 1 cm were observed only rarely. It is trigonal, space group R-3, with unit-cell parameters refined from PXRD: a 9.362(2), c 36.470(12) Å and V = 2768.3(1.2) Å3. Chemical analyses of zeophyllite correspond to the empirical formula (Ca12.84Na0.07)Σ12.91(Si9.83Al0.26)Σ10.09 O28(OH)1.43 F8.42· 6H2O. Tobermorite occurs as snow-white hemispherical to spherical aggregates up to 1 cm in size, it replaces earlier zeophyllite. It is monoclinic, space group Bm, with unit-cell parameters refined from PXRD: a 6.714(4), b 17.375(4), c 22.670(8) Å, γ 123.31(3)° and V 938.2(1.3) Å3. On the base of chemical analyses, tobermorite with empirical formula (Ca4.55Na0.03K0.02)Σ4.60(Si5.40Al0.60)Σ6.00O15.56(OH)1.44·5H2O is accompanied by more rare Ca-poor kenotobermorite with empirical formula (Ca3.99Na0.04)Σ4.03(Si5.60Al0.40)Σ6.00O14.62(OH)2.38·5H2O. Fluorapophyllite-(K) forms abundant prismatic crystals up to 0.5 - 2 cm in size. It is colorless to white with vitreous to greasy lustre. It is tetragonal, space group P4/mnc, with unit-cell parameters refined from PXRD: a 9.0157(13), c 15.7889(19) Å and V = 1283.4(3) Å3. Chemical analyses of fluorapophyllite-(K) correspond to the empirical formula (K0.81Na0.24)Σ1.05Ca4.06(Si7.25Al0.47)Σ8.00O20F1.05· 8H2O. Other zeolites, thomsonite-Ca, chabazite-Ca, phillipsite-Ca and -K, were found in association; their PXRD data, unit-cell parameters and chemical compositions are given in the paper.