This sill outcrops in the Longue Pointe area of the City of Montreal and extends over about 2.5 km in a north-northwest- south-southeast direction with a width of some 500 m. Other sill outcrops occur within the city further to the north-northwest. About 8 m thick the sill is a tinguaite with phenocrysts of aegirine, nepheline, hauyne and orthoclase in a syenitic matrix.
CLARK, T.H. 1952. Montreal area Laval and Lachine map-areas. Geological Report, Quebec Department of Mines, 46: 1-159.