Natriumfeldspäten

Natriumfeldspäte, or sodium feldspars, are a group of feldspar minerals in which sodium (Na) is the dominant alkali cation in the crystal structure. The principal endmember is albite (NaAlSi3O8). Alkali feldspars form a continuous solid solution with potassium feldspars (KAlSi3O8), so natural samples often have compositions between Na- and K-rich members. The term Natriumfeldspäte emphasizes the sodium-rich end of this feldspar family.

Geochemically, natriumfeldspäte belong to the tectosilicate feldspar group. They share the characteristic framework of interconnected SiO4 and AlO4 tetrahedra, with alkali cations occupying large channels in the structure. The crystal chemistry leads to variations in ordering and symmetry as composition and temperature change. In many rocks, natriumfeldspäte occur as part of the alkali feldspar family alongside potassium feldspars and mixed Na-K compositions.

Occurrence and texture, natriumfeldspäte are common in felsic igneous rocks such as granites, rhyolites, and pegmatites, and they may be found in granitoid metamorphic rocks. They commonly occur together with quartz and other feldspars. In weathering profiles, natriumfeldspäte can alter to clay minerals such as kaolinite and produce soluble ions in solution.

Economic and practical aspects: natriumfeldspäte are mined as sources of aluminosilicate minerals for ceramics and glassmaking. They are also used in various industrial applications where sodium-containing feldspars are advantageous. Their occurrence, composition, and alteration products can be important indicators in geological mapping and rock classification.