Feldspars and Feldspathoids

The feldspars form the most abundant group of minerals in the crust of the Earth and Moon and also occur in many meteo­ rites. They playa fundamental role in all rock-forming processes at shallow depths, but are rare or absent from the upper mantle. Their detailed study is thus essential for the understan­ ding of such varied processes as magma genesis and differentia­ tion, metamorphism, al terat...