The Arkansas bauxite deposits, the most important in the United States, are surface deposits overlying nepheline-syenite, an igneous rock with a high ratio of alumina to iron content.
"The Economic Aspect of Geology"
C. K. Leith
Canadian corundum occurs as a constituent of syenite and nepheline-syenite in Lower Ontario.
"The Economic Aspect of Geology"
C. K. Leith
301. Composite rocks are definite associations of certain crytonostic, simple minerals, as feldspar, mica, solid silex, augite, and nepheline.
"COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1"
Alexander von Humboldt