This is a body of about 4.5 km2 elongated northwest-southeast and intruded into Precambrian granites of the Tres Corregos complex. Itapirapua comprises mainly nepheline syenites with lesser amounts of melteigite, malignite, pulaskite, mariupolite and carbonatite; dykes of tinguaite are present within and around the intrusion and some marginal fenitization occurs. The nepheline syenites contain aegirine-augite/aegirine, studied by Gomes et al. (1970), and much cancrinite, some sodalite and melanite, zoned examples of which were investigated by Gomes (1969); biotite, wollastonite, pectolite, fluorite, eucolite, pyrite, pyrrhotine, calcite and zeolites also occur. Analyses of a range of rocks are given by Gomes and Dutra (1970). The carbonatites, which form small dykes and veins, are orthoclase sovites and apatite-orthoclase sovites. They are confined to the central part of the intrusion where they cut nepheline syenite; analyses are available in Gomes and Dutra (1969). The fenites include aegirine-augite and alkali-amphibole-bearing varieties.