INDUSTRIAL
MINERALS
INDUSTRIAL MINERALS
Introduction. Tanzania is endowed with a variety of industrial minerals
such as clay, diatomite, fluorite, glass sans, graphite, gypsum, kaolin,
kyanite, limestone, magnesite, phosphate, rock salt, soapstone, soda ash,
and many others. The development of these minerals is, however, in its
infancy. Small quantities of some of the minerals, such as limestone, clay
and gypsum, are consumed in local industries.
EVAPORITES
Introduction. A number of enclosed basins occur in Tanzania, mostly in
semi-arid areas where drainage to the sea has been disrupted by Cenozoic
faultin related to Rift Valley formation. Many of these have saline lakes
or mud flats in them. Lake Natron is a well-known example; Having brines
rich in sodium carbonate and chloride. Harris (1961) mentions several
others. Trona (hydrated sodium carbonate/bi-carbonate) is harvested on a
commercial scale from Lake Magadi, Kenya, close to the Tanzanian border
near Lake Natron. Salt is produced from several areas in Tanzania both
from seawater evaporation and salt springs inland as at Uvinza.
A
number of other enclosed or partially enclosed basins are worth
investigation for brines or salts, either for export or for use in
domestic industries. In addition, great thicknesses of rock salt have been
discovered in drill holes in Jurassic strata of the Mandawa coastal basin.
The other evaporate resources are principally located in enclosed basins
of the Eastern Rift Valley, although other salt occurrence are also known.
Several are discussed in reports by Harris (1961), as well as by ESAMRDC
(1982 & 1983).
Lake Natron.
Like Lake Magadi in Kenya, this sizeable lake has
long been considered a potential source of sodium carbonate. The lake
brines contain (anhydrous basis) 20.1% Na2CO3, 11.2% NaCL, 0.41% K, 0.25%
Na, and other constituents. The water is surrounded by a salt crust up to
a metre thick with an average composition (anhydrous basis) reported as
58.6% Na2CO3, with lesser amounts of sodium bicarbonate, sodium sulphite
and sodium chloride. The sodium fluorite content of 1.78%, high due to the
volcanic origin of most of the salts, is a potential quality problem.
Investigations have resulted in an estimate of 168 million tonnes of total
salts in the crust and brines. Problems of access, energy supply, and
distance from markets have delayed development of the resource.
Lake Eyasi.
The southwest part of this enclosed lake contains
salt crusts and brine pools with carbonate, bicarbonate, chloride, and
sulphateof sodium, calcium chloride. The total dissolved solids in some
brine pools are reported to be 432 g/l, with about 80% as sodium chloride.
The sodium fluoride content of 0.4% in salt crusts is too high for human
consumption.
Lake Balangida.
The lakke is situated in north central Tanzania, 80
km south of Lake Eyasi in the Eastern Rift Valley. Preliminary estimates
show total reserves of 580,000 tonnes consisting of 225,000tonnes of
sodium chloride, 132,000 tonnes of sodium sulphate, 121,000 tonnes of
sodium bicarbonate, and 15,000 tons of potassium chloride and 1, 800
tonnes of sodium phosphate.