A primary deposit of tin and tungsten has been discovered in association with granites of the Cambrian (?) sub-volcanic igneous complex at Sabaloka, on the Nile north of Khartoum. Wolfram and cassiterite occur in a stockwork of quartz veins which also contain minor amounts of sulphide minerals. The stockwork centres around a small intrusion of primary greisen lying on the contact of a porphyritic microgranite ring-dyke but the greisen and mineralizing solutions are believed to have originated from a nearby mass of biotite-muscovite granite. The deposit has many features in common with the primary tin veins associated with the Younger Granites of northern Nigeria and other parts of northern Africa.