One of the most common feldspathoid minerals, potassium aluminosilicate (KAlSi 2 O 6 ).
It occurs only in igneous rocks , particularly potassium-rich, silica-poor, recent lavas. Some important localities include Rome, Italy; Uganda; and Wyoming's Leucite Hills. Leucite is used as a fertilizer in Italy (because of its high potassium content) and as a source of commercial alum.