Any of a group of alkali aluminosilicate minerals similar to the feldspars in composition but having a lower silica-alkali ratio or containing chloride, sulfide, sulfate, or carbonate.
Their physical and chemical properties lie between those of the feldspars and zeolites . The most abundant feldspathoids are nepheline and leucite. Other significant varieties include kalsilite, sodalite, nosean, and haüynite. Feldspathoids are found chiefly in igneous and metamorphic rocks; they are used as raw materials in the production of alum, glass, and ceramics.