Eight small plugs of olivine nephelinite ranging from 200-500 m diameter occur in the vicinity of Asuncion and up to 15 km distant. They comprise about 35% olivine, 35% pyroxene, 10-15% magnetite, 10% nepheline and a little zeolite, mostly in veins. (J.H. Palmieri, personal communication, 1981). Large inclusions of olivine are common, while very small nodules of lherzolite also occur. Names of individual plugs are Nemby, Lambare, Tacumbu, Verde, Confuso, Barcequillo, Ramirez Isla and Puerto Botanico.