A cancrinite-arfvedsonite pegmatite occurs on two small islands in a narrow arm along the north side of Nachicapau Lake. Arfvedsonite crystals up to 2x0.2 cm lie in a groundmass of cancrinite and very fine grained magnetite. Analyses of the rock, cancrinite and arfvedsonite are available (Dressler, 1981, p. 1761). Possibly related to the Castignon Lake occurrence (No. 150) which is some 40 km further west.