An area of microcline-amphibole gneisses lies along the coast north of Beio and these are described by Champetier de Ribes and Reyre (1959) as being of the same type as the gneisses of Nkonglong (No. 34). However, no petrographic details are given.
CHAMPETIER DE RIBES, G. and REYRE, D. 1959. Notice explicative sur la feuille Yaoundé-Ouest. Carte Géologique de Reconnaissance à l'échelle du 1/500,000. (O21) République du Cameroun. Paris.