Hadjer el Hamis and Hadjer Bigli comprise several rocky pinnacles close to the southern shore of Lake Chad and immediately east of the Chari river; they are up to about 100 m high. The rocks are principally comendites and probably extrusive. They are glassy with phenocrysts of quartz, sanidine, magnetite, aegirine and sodic amphibole, which is generally arfvedsonite but sometimes with a little riebeckite. Facies with spherulitic and micrographic textures also occur. A whole rock analysis is given by Garde (1911).