Effect of the composition of zeolite paranatrolite on the configuration of its water-cation subsystem

The Rietveld method is used to determine the structure of two samples of high-hydrated zeolite paranatrolite: {Na1.15Ca0.38Sr0.04(H2O)3.1}[Al2.19Si2.81O10] (Vishnevye Mountains, Urals) and {Na2.01K0.04H0.04(H2O)3.8}[Al2.10Si2.90O10] (Kirov Mine, Khibiny Massif). Paranatrolite from the Vishnevye Mountains is characterized by the presence of split water positions and a relatively low total H2O content. Local water-cation assemblages (WCAs) of three configurations are identified in the statistical “mixture”. The extraframework subsystem in the structure of Khibiny paranatrolite is made of WCAs of one configuration. The H2O content of this mineral is close to the maximum possible amount and is a recordbreaker for natrolite-type minerals.