Albite (Ab, NaAlSi3O8), anorthite (An, CaAl2Si2O8) and microcline (Mc, KAlSi3O8) are the major feldspar minerals that are abundant in various geological environments. Recently, we have discovered new HP polymorphs of An, Ab and Mc at pressures above ~10 GPa. In our further investigations, by means of in situ HP SCXRD measurements, we plan to address elastic softening of feldspars in pre-transitional pressure range, hysteresis of the phase transitions, and amorphization mechanism of alkali feldspars. Our results will provide mineral physics contain on behaviour of one of the major components of cold and ultra-cold slabs and their seismic activity.