Tapira is an almost circular intrusion about 6 km in diameter emplaced in Precambrian quartzites of the Canastra Group, which strike parallel to and dip away from the contact. The complex is deeply weathered for between 30 and 200 m. The distribution of rock types is not fully known, but part of the claims of the company V.A.L.E.P. have been explored in detail by drilling, trenching etc. which indicated that fresh rock consisted of 80% ultrabasics, mostly diopsidic pyroxenites, 5% potassic felsic rocks, principally trachytes and syenites, 3% sovite and 12% secondary quartz-rich rocks (silexite). The pyroxenite is micaceous and rich in apatite and perovskite, with minor magnetite, ilmenite, melanite, olivine and sphene. Locally olivine predominates to give dunites and phoscorites. A melilite-rich rock (uncompahgrite) has also been described (Guimaraes et al. 1980) containing 63% melilite, together with phlogopite, apatite, opaques, diopsidic augite and perovskite. A further rock type is composed dominantly of apatite with abundant perovskite and subordinate sphene and magnetite. Dyke rocks include bostonites: an analysis of one gave 14.4% K2O (Alves, 1960, p. 17). Herz (1976, p. 6) describes perovskite occurring in veins and disseminations in the country rock. An irregular fenite aureole extends for up to 2.5 km.