Bishusha

2.5 km northwest of Bishusha on the eastern side of the Bigogo River, Denaeyer (1958) noted the occurrence of nepheline syenite. Details of the extent and field relationships are not available. The rock comprises microcline perthite, nepheline, which may have inclusions of sodalite with a dactylotypic texture, green biotite, locally muscovite replacing nepheline, melanite, titanite and accessory apatite. Another variety of the rock contains more sodalite and a sodic amphibole described as 'osannite' (now riebeckite). Biotite syenites and granites outcrop three kilometres west of Bishusha the former being exceptionally sodic (8.01% Na2O; 0.71% K2O), but they are not peralkaline. Rock analyses are given.