Mine excursion
Both open pits are mined in phases. In picture is a truck hauling material from the bottom
of the Otjikoto Pit during Phase 2, which was in full swing when Mining Mirror visited.
license in December 2012 and started
construction a mere four months later.
The first gold was poured two years later
in December 2014 and the mine started
commercial production on 1 March 2015.
Hopes for exploration
Otjikoto and Navachab are not the
only gold deposits in Namibia. Several
exploration companies have set up base
here. In fact, results from several gold
exploration projects around the country
have been good and it is only a matter of
time before Namibia’s third gold mine
sees the light.
B2Gold is currently doing exploration
work at the Otjikoto area and also at
Ondundu, in the Omaruru region, which
is almost halfway between Navachab
and Otjikoto. According to Mark Dawe,
country manager and managing director
of B2Gold Namibia, the company’s total
exploration budget in 2018 is USD5.1-
million. “Exploration in 2018 will include
17 000m of diamond drilling and
4 000m of rotary air blast (RAB) drilling,
split between the Otjikoto Mine, the
Ondundu, and other projects,” says Dawe.
Dawe, a metallurgist by training, and his
team at the Otjikoto Mine have managed
to squeeze the proverbial blood from a
rock. The B2Gold team and the Australian
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engineering company Lycopodium have
designed an efficient processing plant that
boasts an average of 98.6% recovery for the
YTD 2018 recovery rate (project to date
is 98.4%) — an exemplary performance
under challenging conditions.
Efficient management
Eric Barnard, acting general manager
at Otjikoto and also a metallurgist, tells
Mining Mirror that Otjikoto does not
have the luxury of high-grade ore and
therefore, the strategy is to manage the ore
body and the plant feed as efficiently as
possible. “We have to ensure that we mine
the right grades at all times so that we can
meet our production targets,” says Barnard.
A low-grade operation like Otjikoto is
never able to stockpile high-grade material
for a rainy day. For management, this
means constant planning.
“To make such a low-grade operation
work, one has to mine selectively,” says
Peter Mawoyo, production manager
at Otjikoto. “That includes the mining
process in the two pits, and processing the
material in the plant,” he adds.
“We control the blend into the plant
to ensure correct grade as well as to
maximise recoveries during periods that
we are fed with ore containing a high
percentage of pyrrhotite. One of the
criteria behind the need to carry selective
grade control is to stabilise the percentage
of sulphur contained in minerals such
as pyrrhotite, thereby maximising gold
recovery,” Barnard explains.
Barnard says that when he first saw the
mineralogy of the ore, he did not believe
that recoveries in the high 90s could be
achieved through a conventional mill/
leach gold processing plant. Because the
ore at Otjikoto contains a high component
of gravity recoverable gold (GRG), a
plant was designed with a gravity circuit
yielding exceptionally high recoveries.
The grade at Otjikoto, nonetheless,
remains low at about 1.6 grams per tonne.
To recover the gold, Otjikoto mines a lot
of waste, and moves on average about 106
000 tonnes of material per day, of which
only approximately 10 000 tonnes are
milled — thus at a high average stripping
ratio of approximately 11:1, excluding the
low-grade ore and approximately 7:1 if
the low grade ore is taken into account.
According to the original bankable
feasibility study, the plant should operate
at a recovery of about 96.7%. In addition
to the higher recovery rates, the plant is
processing more material than originally
designed. The mining team is pushing
3.3 million tonnes run of mine (ROM)
through the plant, while the plant was
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