Sources/Uses
Composed of sodium, potassium, and aluminum silicate; [Merck Index] "Nepheline, also called nephelite (from Greek: νεφέλη, 'cloud'), is a feldspathoid: a silica-undersaturated aluminosilicate, Na3KAl4Si4O16, that occurs in intrusive and volcanic rocks with low silica, and in their associated pegmatites." [Wikipedia]