Eight kilometres south-southwest of Nkonglong, at a locality referred to by Champetier de Ribes and Reyre (1959) as 'Mont de l'Elephant', is a conformable, 5 km long lens of nepheline-bearing gneisses depicted on the 1:500,000 geological map (Champetier de Ribes, 1959) as ' 'syenite microclinique a amphibole'. The rock is coarse, with grains up to 3 mm diameter, foliated and gneissose with alternating feldspar, pyroxene and amphibole layers. It is composed of microcline, albite, up to 25% nepheline, aegirine and amphibole with accessory biotite, fluorite, cancrinite, carbonate, lavenite and chevkinite. The amphibole is mboziite, two analyses and optical data for which are given by Kornprobst et al. (1976), who also give analyses of a pyroxene and a whole rock. Peralkaline syenites are also described by Champetier de Ribes and Reyre (1959) from the area northeast of Lolodorf, which is 75 km east-northeast of Nkonglong. These gneisses are dominantly composed of alkali feldspar with prisms of aegirine-augite.