Microprobe analyses and unit cell dimensions are tabulated for gismondines from 17 localities. Their chemical composition varies only slightly from the stoichiometric formula Ca4Al8Si8O32.18H2O. The Si/(Al + Si) ratio varies from 0.514 to 0.542; Ba, Fe and Mg are always absent and K, Na and Sr are low or absent. The K-rich analyses in the literature are explained by the frequent occurrence of phillipsite-gismondine intergrowths. No correlation between the relatively constant cell dimensions and chemical composition was found. The strongest correlation is between Si/(Al + Si) and (Na + K)/(Na + K + Ca). The narrow range of chemical variation in this zeolite is attributed to the ordered (Si,Al) distribution. TG and DTG curves are given for one gismondine.-R.A.H.
The crystal chemistry of gismondines: the non-existence of K-rich gismondines / Vezzalini, G.; Oberti, R.. - In: BULLETIN DE MINERALOGIE. - ISSN 0180-9210. - 107:6(1984), pp. 805-812. [10.3406/bulmi.1984.7822]
The crystal chemistry of gismondines: the non-existence of K-rich gismondines
Vezzalini G.;
1984
Abstract
Microprobe analyses and unit cell dimensions are tabulated for gismondines from 17 localities. Their chemical composition varies only slightly from the stoichiometric formula Ca4Al8Si8O32.18H2O. The Si/(Al + Si) ratio varies from 0.514 to 0.542; Ba, Fe and Mg are always absent and K, Na and Sr are low or absent. The K-rich analyses in the literature are explained by the frequent occurrence of phillipsite-gismondine intergrowths. No correlation between the relatively constant cell dimensions and chemical composition was found. The strongest correlation is between Si/(Al + Si) and (Na + K)/(Na + K + Ca). The narrow range of chemical variation in this zeolite is attributed to the ordered (Si,Al) distribution. TG and DTG curves are given for one gismondine.-R.A.H.
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