The identification and determination of plagioclase felspars by the X-ray powder method

Abstract

There appear to be few published data correlating X-ray powder patterns of chemically analysed plagioclase felspars with composition. Tuttle and Bowen (1950) have examined the powder patterns of low-temperature and high-temperature modifications and find that pure albite from Amelia, Virginia, when heated for ten days at 1050 ° C., gives a powder pattern identical with that of synthetic albite. They have not given, however, complete data over the whole range from An 0 Ab 100 to An 100 Ab 0 . Claisse (1950) selected six reflections from the powder patterns of eight plagioclases of composition extending over the complete range, and plotted line separations against composition determined optically, but did not distinguish between high- or low-temperature forms.