A new mineral, gismondine-Sr with ordered gismondine framework type (B2212 no. 20, Z= 1; a = 14.0256(2) Å, b = 10.45900(10) Å, c = 13.79360(10) Å), V= 2023.44(4)Å 3 ) and the following ideal chemical formula Sr4(Si8Al8O32)•9H2O was discovered in amygdaloidal voids of partly melted gehlenite hornfels at Halamish locality, Hatrurim Basin of the Hatrurim Complex, Negev Desert, Israel. Gehlenite hornfels is mainly composed of gehlenite, wollastonite, and garnet of the grossular-andradite-schorlomite series. In a low-temperature association occur minerals such as thomsonite-Ca, flörkeite, analcime and minerals of the tobermorite supergroup. Gismondine-Sr forms spherulitic aggregates up to 180 μm and, rarely, pseudotetragonal bipyramidal crystals up to 50 μm. Empirical crystal chemical formula of gismondine-Sr is as follows (Sr2.02Ca1.09Ba0.02K0.72Na0.62)∑4.47Al7.91Si8.09O31.85•9H2O.
Flörkeite, a rare zeolite with PHI (phillipsite) framework type, was found in numerous amygdaloidal voids in pyrometamorphic rocks of the Hatrurim Basin, Hatrurim Complex, Israel. This is the second reported occurrence of flörkeite previously found in a Ca-rich xenolith from a quarry at the Bellerberg volcano near Ettringen, East Eifel volcanic area, Germany. The mineral with the empirical crystal chemical formula (K2.91Ca2.00Na0.91)[Al7.96Si8.04O31.94]·12H2O (P-1, no. 2, a=19.9366 2, b=14.2517 1, c=8.89350 10 Å, α=88.2480 1, β=125.0960 10, γ=89.6350 10, V=2019.19 4 Å3, and R=3.41%) did not show significant differences with respect to that of the type locality. The Raman spectrum of flörkeite is here reported for the first time. No significant differences are noticed compared to phillipsite-K. The main band ~470 cm-1, characteristic of the PHI-type structures, is independent on framework order and Si/Al ratio. The zeolite mineralization of amygdules in pyrometamorphic rocks results from meteoric water circulations in Al-rich rocks during their cooling. The crystallization sequence of zeolite corresponds to the Ca/(K+Na) ratio decrease. Flörkeite formed at the end of a low-temperature crystallization sequence, indicating the predominant role of potassium in crystallization. The occurrence of flörkeite in different pyrometamorphic rocks implies the relatively uniform, regional mineral-forming conditions, and open hydrologic system of zeolitization. In pyrometamorphic rocks of the Hatrurim Basin, the process of zeolitization is characterized by low silica activity and high pH conditions.
Gismondine-Sr, recently discovered in the Hatrurim Complex in Israel, has been recognised in a xenolith sample from the Bellerberg volcano in Germany. The empirical crystal-chemical formula indicates elevated K content: (Sr1.74Ca1.05Ba0.09K1.56Na0.49)∑4.93[Al7.98Si8.06O32]•9.62 H2O. Additionally, Ba-rich gismondine and amicite have been found in the low-temperature mineral association of the pyrometamorphic rock from the Hatrurim Complex. The Raman spectra of the studied zeolites and the crystal structure of gismondine-Sr from the second occurrence are presented. An insightful review of zeolites with GIS framework-type structure led to the following conclusions: 1) garronite-Na and gobbinsite are equivalent and constitute a solid-solution with garronite-Ca; 2) gismondine-Ca, -Sr, and amicite belong to one mineral series; 3) two zeolites series with different R-factor (defined as Si/(Si+Al+Fe)) can be distinguished within GIS topology: the garronite series (R > 0.6) including garronite-Ca and
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