At least 12 of a much larger number of radioactive anomalies in the Bambui area prove to be pipes up to about 100 km in diameter, which are usually filled with breccia. The rock of one pipe is described as "soda-minette" but consists of alkali feldspar, aegirine, alkali amphibole, mica, nepheline, secondary analcime, apatite, sphene, pyrite and opaques. They are probably related to the Serra do Bueno necks and dykes lying to the north.
CORREA, G.W. 1971. Diatremas na regiao de Bambui. Anais Congresso Brasileiro de Geologia, 25(1): 103-12