stripes
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).
BARBEAU, J. 1956. Notice explicative sur la Feuille Fort-Lamy. Carte Géologique de Reconnaissance à l'échelle de 1.1,000,000. Gouvernement General de l'Afrique Equatoriale Française.GARDE, G. 1911. Déscription géologique des regions situées entre le Niger et le Tchad. Thesis, University of Clermont-Ferrand. A. Hermann et Fils, Paris. 284 pp.GENTIL, L. 1904. Sur l'existence de roches alcalines dans le centre Africain. Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences, Paris, 139: 413-5.