Forelesninger holdt ved Advanced Study Institute of Feldspar - Oslo 1962
Lectures held at Advanced Study Institute of Feldspar - Oslo 1962
Most of the work on feldspars during the recent years has been concerned with structural arguments and the problem of the relative stabilities of the different polymorphic forms of the feldspar minerals. The word "polymorphs" implies, of course, different structural forms with identical composition. However, the composition is often unknown, and only assumed to be the same, and the extent to which a feldspar polymorph may be stabilized by compositional difference has not been fully discussed. The question is important when the data obtained in the laboratories on pure synthetic compounds, or from heat treatment of natural compounds whose compositions are not allowed to vary with temperature, shall be applied to natural feldspars whose compositions as well as structures are dependent on the temperature. It is therefore within the scope of this seminar to discuss the geochemistry of the feldspars, and to delineate the "normal" concentrations of their most important trace elements.