More than 900 pegmatites were sampled during a tin exploration programme conducted along the Omaruru River in western central Namibia. The pegmatites are hosted by late Precambrian metasediments of the Damara Sequence and are probably of Cambrian or somewhat younger age. The pegmatites sampled occur in a belt 60 km long by 5 km wide which represents the bulk of what is known as the central tin belt, a sub-province within a greater tin province covering some 24,000 km2. Although there are S-type granites in the vicinity, there is a closer spacial association between tin-bearing pegmatites and a stratigraphic unit which will for convenience be referred to as the 'tin schist'. This unit consists mainly of knotted, quartz-biotite schist which is in part tourmaline-bearing. The same rock-type is also present 40 km to the northwest at the Uis tin mine, the largest producer in the region. The tin schist has a very distinctive satellite imagery signature and this makes it possible to trace its regional distribution, which matches that of tin deposits to a remarkable degree. Richards (1986) stated that the tin schist contains anomalous concentrations of tin irrespective of whether any pegmatites or granites occur in close proximity or not. The possible genetic meaning of this association and the observed distribution pattern of tin deposits in the greater tin district are discussed.