Nepheline syenite gneiss occurs in the core of a recumbent nappe, where it forms a conformable lenticular body with the central thickest portion high on Trident Mountain. The gneiss, in addition to nepheline, includes perthitic K-feldspar, albite, biotite and aegirine.
CURRIE, K.L. 1976a. The alkaline rocks of Canada. Bulletin, Geological Survey of Canada, 239: 1-228.