Lessons from the past
The rebirth of tin
Tin is one of the
earliest metals
known and used
by humankind.
Recently, there
has been a
renewed interest
in the metal.
D
espite ups and downs in the tin price
throughout the years, the long-term
value of this metal looks secure, and
demand is expected to continue growing. With the
development of Alphamin’s Bisie tin project close
to Goma in the eastern part of the Democratic
Republic of the Congo (DRC), AfriTin’s reopening
of the Uis project in Namibia, and a number of
exploration companies drilling for possible tin
deposits in Nigeria, this enigmatic metal has drawn
some attention from several investors interested in
diversifying their African portfolios. Although the
tin sector hardly ever makes news headlines, and
despite the gap in geological research about tin, it
has been mined for many centuries in Africa.
According to a paper “Tin in Africa” by Judith
Kinnaird, Paul Nex, and Lorenzo Milani, tin was
used in bronze implements as early as 3500 BCE,
although the pure metal was not used until about
600 BCE. Tin is a soft, silvery white, highly
malleable metal with a low melting point of
232˚C. It is used for solder, tin plating, bronze,
brass, and pewter, as well as in the chemicals
industry. According to the authors, “Several
governments recognise tin as strategic to the
needs of their technological industries for its use
as a tin-indium oxide in electronic touch screens.
Because of its hardening effect on copper, tin
was used in bronze implements in Africa for
many centuries. “In Nigeria, exquisite bronze
artefacts from three sites in the Igbo-Ukwu area,
Anambra State, have been dated to the ninth
century AD. These predated the more famous
Benin bronzes, with early sculptures dating from
the thirteenth century but a large part of the
collection originating in the fifteenth and sixteenth
centuries.” (Kinnaird et al.)
According to the research by Kinnaird et al.,
significant African tin production began at the
[34] MINING MIRROR JULY 2018
Expectations are high for Alphamin’s
high-grade Bisie tin project in the DRC.
beginning of the twentieth century and maximum
output was reached in the 1970s. Since then,
production has declined to less than 2% of the
world’s output.
Here follows an extract from the paper “Tin in
Africa”, which was published in The Great Mineral
Fields of Africa in September 2016 and was edited by
Richard Viljoen.
Across Africa, deposits range in age from Archaean
in Zimbabwe and Palaeoproterozoic in South Africa,
to Mesozoic and Pleistocene in Nigeria. Major eras of
tin mineralisation, however, are related to continental
amalgamation at the end of the Proterozoic era, with
deposits in Neoproterozoic pan-African belts in Namibia,
Nigeria, Rwanda, Somaliland, the DRC, and Zimbabwe.
In the Mesozoic, cassiterite mineralisation was associated
with voluminous granite magmatism during Gondwana
fragmentation in Nigeria, Cameroon and Namibia. Tin
provinces occur in Nigeria, South African and Namibia,
where the cassiterite mineralisation occurs within rocks of very
different ages.
The style of tin deposits includes disseminations in granite
cupolas, lode-style mineralisation, either as endogranitic or
exogranitic veins, rare metal pegmatites, veins not directly
associated with granites, and as eluvial and alluvial deposits.
Pegmatite occurrences occur in Nigeria, Namibia, Rwanda,
DRC and Zimbabwe while granite-hosted and stockwork
deposits have been noted in Nigeria, Cameroon, South Africa,
Namibia, Sudan and Egypt. Vein and lode-hosted deposits are
found in Morocco, Nigeria, Rwanda and Somaliland. Alluvial
deposits occur in Nigeria, Cameroon and the DRC .
Source: “Tin in Africa” by Judith A.
Kinnaird, Paul A.M. Nex, and Lorenzo
Milani – EGRI, School of Geosciences,
University of the Witwatersrand.