As nouns the difference between leucite and tephrite

is that leucite is a mineral of silica-poor igneous, plutonic and volcanic rocks. Chemically, leucite is a potassium feldspar with insufficient silica to satisfy the chemical bonds. Because of the unfilled bonds, leucite weathers rapidly and can only be seen as inclusions in freshly broken rock while tephrite is an igneous rock consisting essentially of plagioclase and either leucite or nephelite, or both.