Although one of the Monteregian intrusions, Rougemont contains few alkaline rocks. The main mass comprises feldspathic peridotite, although G.N. Eby (personal communication, 1984) says that this area consists essentialy of pyroxenite and gabbro, and areas of layered and hornblende gabbros. Dykes are relatively abundant within the intrusion and collar of hornfelses. There are olivine-pyroxene-phyric dykes confined to the hornfelses, fine- grained non-porphyritic gabbros and camptonites with ocelli (Philpotts, 1976, p. 1154) for which trace element data of ocelli and matrix have been determined (Eby, 1980).