Apart from Semarule (No. 1) there are elsewhere within the Gaborone granite facies that are peralkaline, although the distribution of these rocks is not well known. The Kgale granite, for instance, particularly near its margins and in certain granophyric facies, contains aegirine-augite and riebeckite (Grobler, 1996). A group of peralkaline rhyolites forms part of the Kanye Formation which is distributed as a linear belt some 150 km long around the eastern and southern margins of the Gaborone granite. Smaller areas occur southwest and south of the granite. Some of these rhyolites contain aegirine. A small part of the Gaborone granite and part of the Kanye Formation, including the Vlakpan structure immediately to the north of Mafikeng, lie within South Africa. A general account of the distribution of these peralkaline rocks is given by Grobler (1996).