MINERALIZATION

The Mweza Range contains a core of metasediments with inclusion of banded ironstones, phyllites, sericite-quaartz schist and quarzites, all tightly folded. Narrow peridodites sills, altered to serpentinites and allied rocks, intrude in older rocks. Range rocks are flanked by basalts and dolerites metamorphosed into greenstones and epidorites. Granites and associated pegmatites intrude the range rocks with emeralds occurring in tremolite schists adjacent to the granitic pegmatites. Many of these pegmatites contain: beryl, lepidolite, petalite, spodumene and Ta-Nb species. Local metamorphism is believed responsible for the formation of emeralds.