The potash-soda-felspars. I. Thermal stability

Abstract

In a previous paper (24) the writer discussed the relations between the chemical and physical properties of a number of potash-sodafelspars, mainly of the schillerized or perthitic variety, and the effect of high temperatures upon them. The present paper gives the results of further examination of these and of several additional specimens selected to make the range of composition more complete.Twenty-six specimens were selected for this investigation. They include two albites, six microclines, and eighteen felspars which have been grouped as an orthoclase-microperthite series. The confused nomenclature of the alkali-felspars makes a choice of suitable names difficult. Alling's classification (1, pp. 253-254) represents a systematic attempt to overcome this confusion, but it seems doubtful whether some of his arbitrary subdivisions (e.g. ‘anorthoclase potentially eutectoperthite’ and ‘microcline eutectoperthite’) can exist.