Alkaline Rocks and Carbonatites of the World

Setup during HiTech AlkCarb: an online database of alkaline rock and carbonatite occurrences



Occurrence number: 
Longitude: 14.02, Latitude: -10.73

Chamaco forms a mountain feature, but no other details of field relationships have been traced. The rocks are described as aegirinite, lusitanite, umptekite and nordmarkite (Andrade, 1955), and the term angolaite was coined for a peralkaline syenite (Andrade, 1954). The aegirinite comprises 83% aegirine, 10% orthoclase and 6% magnetite. The lusitanite consists of alkali feldspar and aegirine with accessory apatite and calcite, while the angolaite contains 87% alkali feldspar, 5% titanaugite with aegirine-augite rims, 0.7% aegirine, 3.6% fayalite and accessory magnetite, apatite, aenigmatite, hastingsite and cancrinite. Rock analyses are given in the references cited.


ANDRADE, M. de 1954. Contribution à l'étude des roches alcalines d'Angola (note preliminaire). 19th International Geological Congress, Algiers. Comptes Rendus, 19: 241-52.ANDRADE, M.M. de 1955. Novo subsidio para o estudo das rochas alcalinas de Angola. Garcia de Orta. Revista da Junta das Missões Geográficas e de Investigações do Ultramar, 3: 37-46.

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