Aluminum distribution in an igneous maximum microcline and the Sanidine microcline series

Forelesninger holdt ved Advanced Study Institute of Feldspar - Oslo 1962
Lectures held at Advanced Study Institute of Feldspar - Oslo 1962

One of the major efforts in the study of the polymorphism of the potassic feldspar group has been directed at the determination of the order-disorder relationships of silicon and aluminum and the connection of this order-disorder with lattice dimensions and physical properties. The analysis of order-disorder has been based heretofore upon the accurate measurement of the silicon oxygen bond lengths because it had not generally been thought that one could differentiate aluminum and silicon on the basis of their scattering power for X-rays. We noticed in this least squares refinement, however, that the effective scattering factor of the tetrahedral cation is a significant function of the aluminum content, as we observe anomalously low temperature factor values, where a silicon scattering factor is used for an aluminum rich site.