Nepheline

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. It is often found in mica schist and gneiss.