Alto Ligonha

ALTO LIGONHA (RU: Алту-Лигонья) is the region of the rare-metallic granitic pegmatites in Mozambique in the Zambezia province. It includes more than 800 sites, which are grouped into the 60-70 pegmatite fields with the total area of 40 thousand square kilometres. The largest ones are the Muiane, Morrua, Marropino, Monea. The development is performed since the start of the 20th century. Alto Ligonha is known by the finds of the rare minerals: the beryl crystals with the mass of 42 tonnes (the Munyamola 1 deposit), the morganite crystals with the mass of 20-25 kilograms (the Namakotsha deposit), the rubellite drusen with the crystals with the height of 0.5 metres (the Muiane deposit).

The pegmatite bodies of the tabular shape (the length is up to 2,000 metres, the thickness is up to 100 metres) are oriented perpendicular to the lamination of the granite-gneisses, mica and amphibole schists of the pre-Cambrian. The most productive are the bodies with the angle of the dip of the 0-30 degrees to the south. The pegmatites of the plagioclase-microcline-muscovite constitution are albitized, lepidolitized, and kaolinized. The lithium minerals are represented by the lepidolite, spodumene, amblygonite, and petalite; the cesium minerals are represented by the pollucite, cesium micas, cesium beryl; the tantalum minerals are represented by the columbite, mangan-tantalite, ixiolite, stibio-tantalite, microlite, samarskite; the beryllium minerals are represented by the technical beryl, aquamarine, heliodor, morganite, black beryl, emerald, herderite. The major deposits, which are developed, are the Morrua, Muiane, Marropino (80% of the extraction). There have the industrial importance the monazite, euxenite, native bismuth, bismuthinite, scheelite, cassiterite, precious varieties of the tourmaline, muscovite, amazonite, microcline, quartz, kaolinite.

The mining works are performed by the small enterprises within the limits of the weathering zone down to the depth of 10-20 metres with the manual ore development and the benefication on the concentration tables. There have been produced in 1937-79 more than 10 thousand tonnes of the columbite (up to 18% of Ta2O5), columbite-tantalite (18-24% of Ta2O5), tantalite-microlite (42-60% of Ta2O5) concentrates; there have been exported approximately 3 thousand tonnes into the USA, United Kingdom, West Germany, Netherlands, Japan. There have been evaluated in 1979-80 the reserves of the deposits in the Muiane (more than 1000 tonnes of Ta2O5), Morrua (1165 tonnes of Ta2O5 with its content of 464 grams per tonne), Monea (231 tonnes of Ta2O5 with its content of 179-245 grams per tonne). There is expected the integrated development of the deposits with the extraction of the beryl, lepidolite, pollucite, petalite, amblygonite, muscovite, precious stones, and ceramic raw materials.