An elliptical intrusion 8 km in length, Nlonako is surrounded on its northern and western sides by lavas of the Manengouba centre (No. 26) and consists of gabbro, syenite and granite with some rhyolite. The syenites contain some quartz, alkali feldspar, which in some varieties is dominantly albite, biotite, sodic amphibole, which includes both arfvedsonite and riebeckite, aegirine-augite; fayalite occurs in some rocks. The granites are similar with zoned alkali feldspar, arfvedsonite and aegirine. Rhyolites contain abundant alkali feldspar but pyroxene and amphibole have been completely replaced by iron oxides.