Crystallization of Metastable Disordered Anorthite at “Low Temperatures”

Abstract
The determination of order-disorder relations in anorthite ( CaAl 2 Si 2 O 8 ) by the X-ray powder method is described. Metastable disordered anorthite was produced in low-temperature, hydrothermal crystallizations of a glass, as well as by “dry” devitrification atl 100°C. It is concluded that this material is disordered with respect to Al and Si as well as with respect to long-range positioning of the Ca -atoms.