Studies Pertaining to the Mineral Chemistry of Sodalite, Nosean and Hauyne

Abstract

<p> It is claimed in the literature that there is a close connection between sodalite, nosean, and hauyne in their chemical and crystalle-graphic properties and that they may well be isomorphous (Winchell and Winchell, 1951; Barth, 1933). Close relation between the cancrinites and the sodalite minerals of sodalite itself and nosean and hauyne have been implied (Larsen and Steiger, 1916; 1931, 1944). </p> <p> Mixtures of sodalite, nosean and hauyne were made up and heated at temperatures of 100 degrees Celsius to 750 degrees Celsius at pressures ranging from 10,000 to 30,000 psi. Both nosean and hauyne exhibited polymorphism with a cancrinite type of structure below and a nosean or hauyne structure above approximately 475 degrees celsius. Synthetics products of sodalite composition did not show this structural change. </p> <p> The structure of nosean along the cube diagonal was deduced parallel to the 111 plane (along the triagonal axis) which was compared with the cancrinite strcutre as given by both Pauling (1930B) and Kozn and Takane (1933). A possible mechanism for the polymorphism was deduced from projection drawings and scale models. </p> <p> There was no tendency for the synthetic products of these three minerals to dissociate at any of the temperatures and pressures used in this study. Preformed synthetic or naturally occurring sodalite, on the other hand, did have a tendency to dissociate to nepheline although an actual dissociation curve probably does not exist. More likely the water content is the more dominant factor than temperature or pressure. </p> <p> There appears to be complete solid solution between nosean and hauyne but only partial solid solution between sodalite and nosean, and sodalite and hauyne. </p> <p> The substitution of strontium and barium for sodium and calcium is investigated and discussed. </p>