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DIAMONDS
March 2015
MODERN MINING
27
Processing plant at the
Tongo kimberlite dyke
project in Sierra Leone.
Bench stope mining from
surface to 40 m depth will be
used to get Tongo into early
production.
increasing tenfold, yielding in the region of
240 000 carats a year.”
The first results of the trial mining were
reported early in January this year, with
Stellar announcing the recovery of 2 145 car-
ats, including a total of 138 stones greater than
1 carat with the biggest being a 9,2 carat dia-
mond. Gem and near gem diamonds accounted
for approximately 60 % of the diamond popula-
tion recovered. The average grade was 14,6 cpht
(at a +1,25 mm cut-off), slightly higher than
the 13 cpht anticipated based on the historical
exploration and sampling work. The first parcel
of diamonds has been exported to Antwerp and
will probably have been sold by the time this
article is in print. Stellar anticipates the export
and sale of diamonds every two to three months
during 2015.
The trial mining is being carried out using a
smallish fleet of mining equipment consisting
of several 45-t excavators working in conjunc-
tion with 25-t and 30-t articulated dump trucks.
The processing plant is an amalgam of a 100 t/h
DMS plant from the Mandala project and a
5 t/h bulk sampling plant from Droujba. Stellar
retained ADP Metco to reconstruct the plants
and combine them into a fully integrated kim-
berlite processing facility (able to handle both
weathered and fresh material) with primary
and secondary crushing and final recovery via
Flow Sort machines.
“We’re currently running the plant at a
throughput of approximately 50 wet tonnes
per hour on a 2 x 8-hour shift basis,” remarks
Smithson. “This is only half its capacity, so we
do have a lot of flexibility in terms of increasing
the mining and processing rate if we deem it
necessary. After some initial modifications post
commissioning, the plant is now working very
well and is efficiently treating a wide variety of
ore types.”
According to Smithson, the staff and labour
complement at Baoulé now numbers around 70
people. This includes five expats, one of them
being Stellar’s Chief Operating Officer, Rowan
Carr. Like Smithson, he is a geologist who spent
much of his earlier career with De Beers, gain-
ing experience in many of Africa’s diamond
mining countries, including South Africa,
Botswana, Angola, the DRC and the Central
African Republic. As Smithson says, “Most of
our permanent staff are out in the field and we
have only a tiny head office establishment in
London.”
Turning to the Tongo Dyke-1 project in
Sierra Leone, Smithson says Stellar’s inten-
tion is to fast track it into production over the