Graphite is known in many localities. Minor and sporadic production of
graphite has occurred, but not on a sustained basis. The occurrences are
principally within the Usagaran and Ubendian gneiss terranes. The more
valuable coarse-grained graphite
Figure 48: Bahi Swamp, Evaporates
Locality. (Adapted from A, P. Fawley (1954)
Tends to occur in areas of highest
metamorphic grade as reflected by the rough correlation between graphite
district and the granulite terranes (Fig 47). Graphite is discussed in
Harris (1961) and in ESAMRDC (1982 and 1983)
Graphite Opportunities
Merelani.
The Usagaran gneisses, which host
tanzanite mineralisation at Merelani, southeast of Arusha, also contain up
to 20% graphite. More importantly, the graphite is coarse-grained, mostly
of more than 1-mm flake size with several percent in sizes up to several
millimetres. The rock is sufficiently weathered to allow liberation of
coarse graphite-rich excessive combination. The graphite graphite-rich
section is 10-20 m thick. SAMAX, a London-based company, has carried out a
feasibility study on part of the Merelani tanzanite deposit for production
of graphite and tanzanite from gneiss layers, which are stratigraphically
only a few tens of metres, a part.
Production of graphite began in 1995
and 6,679 tonnes of graphite were produced in its first full year of
production in 1996. Production was then suspended and the mine changed
ownership from SAMAX to AFGEM of South Africa, which is currently mining
tanzanite. Sufficient reserves were initially identifies for 40 years
operation at a mining rate of 15,000t/years of high-grade flake graphite
of 97%-98% purity.
Gneisses similar to those at Merelani
are exposed over a large region, and considerable scope exists for
discovery of additional coarse-grained graphite in the area, which is
relatively near highway and the Moshi-Tanga railway line.
Nachingwea District.
Graphite in high-grade gneisses in
the Chiliogali Hills, 10km Southeast of Nachingwea (west of Mtwara)
locally comprises over 20% of graphitic shist bands. Tests reported in
Harris (1961) showed the product to be suitable for manufacture of
crucibles. This area is only about 50 km from the paved part of the Mtwara-
Songea road. Several other graphite-bearing gneisses are reported by
Harris (1961) within or near the Nachingwea granulite terrane (Fig. 47).
Other Graphite Occurrences.
A number of additional prospects are
mentioned in Harris (1961), mostly of small tonnage, low quality flakes,
or both. However, little systematic prospecting has been undertaken. A
systematic compaign, using stratigraphy and metarmophic condition as
guides, could result in significant discoveries.
OTHER INDUSTRIAL MINERALS
Other industrial mineral deposits are
known in Tanzania. Table 7 summarised the major type listed in
alphabetical order.