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MODERN MINING
November 2015
MINING News
ASX-listed Peak Resources reports that
piloting of the beneficiation flowsheet has
commenced on a 66-tonne bulk sample of
typical weathered bastnasite mineralisa
tion collected from the Ngualla rare earth
project in Tanzania. The selection and
piloting of the beneficiation flowsheet is
an integral part of the Bankable Feasibility
Study (BFS) and – says Peak – demonstrates
its commitment to move towards the com
mercialisation of the Ngualla project.
Located 147 km from the city of Mbeya
on the edge of the East African Rift Valley in
southern Tanzania, the project is centered
on the Ngualla carbonatite.
Peak’s Managing Director, Darren
Townsend, commented: “ The com
mencement of the beneficiation pilot
plant is another key milestone in the
development of the Ngualla project. My
congratulations go to the Peak technical
team and their consultants for the com
mencement of this key work programme.”
Peak is developing Ngualla in conjunc
tion with its partners Appian and IFC.
Ngualla is a large high-grade rare earth
deposit that is particularly rich in the high
growth magnet metals neodymium and
praseodymium.
After extensive evaluation of two alter
native beneficiation flowsheets developed
specifically for Ngualla’ s unique minerali
sation, a two-stage flotation process with
an intermediate regrind step has been
selected on the basis of operational advan
tages and lower operating costs.
The flowsheet takes advantage of
a significant proportion of the gangue
(waste) mineralisation being in the form
of relatively large barite particles. An initial
coarse grind (-75 microns) is employed to
liberate the barite and allow its selective
removal using standard flotation tech
niques. Typically, this process stage rejects
Pilot plant for Ngualla rare earth project operational
Commissioning of the barite prefloat circuit of the pilot plant (photo: Peak Resources).
greater than 95 % of the barite whilst
losing only around 10 % of the rare earth-
bearing bastnasite.
The barite-depleted concentrate is then
screened, thickened and sent to a regrind
mill where the particle size is reduced to
less than 45 microns. This provides libera
tion of the bastnasite from iron-bearing
gangue minerals. A second stage of stan
dard flotation is then undertaken at a
temperature of 50°C using dispersants,
gangue depressants and a hydroxamic
acid as a rare earth collector.
The selected flowsheet is the result of
continuous, incremental improvements
achieved in the beneficiation process,
with test work delivering concentrate
grades of between 30 and 50 % rare earth
oxide (REO). These grades represent a
two to three fold improvement over the
16,3 % REO concentrate attained in the
Preliminary Feasibility Study (PFS).
According to Peak, the ability to pro
duce a high grade/low mass mineral
concentrate is expected to have a profound
impact on the overall project economics
by reducing both operating and capital
costs compared to the PFS. This is because
of decreased transportation costs of the
lower mass concentrate; a reduction in
acid consuming gangue mineral content;
and a significant reduction in the size of
the downstream leach recovery plant.
The 66-tonne sample of weathered
bastnasite mineralisation was collected
from eight trenches excavated at Ngualla
earlier in the year and transported to Perth,
Western Australia. This material has been
selected to be representative of the first
five years of mill feed.
Three metallurgical laboratories were
requested to provide proposals for the
construction and operation of a pilot
plant using the two-stage flowsheet. ALS
in Perth was selected based on its piloting
experience, available equipment and tech
nical expertise in rare earth flotation.
Milling of the bulk sample and opera
tion of the first stage barite flotation has
now commenced. The overall operation
of the plant will continue until the end of
the calendar year, producing in excess of
2 tonnes of high grade concentrate to be
used for the downstream leach recovery
pilot plant scheduled to commence in the
first quarter of 2016.
Senior appointments at African Copper
African Copper has appointed Boikobo
Paya, currently a Non-executive Director of
African Copper, as Non-executive Chairman
of the company in succession to Roy Corrans
who retired from the Board with effect from
30 September 2015. It has also announced
the appointment of Thomas Kamwendo as
Chief Executive Officer with immediate effect.
Paya, a Botswana national, was the Per
manent Secretary in the Botswana Ministry
of Minerals, Energy andWater Resources from
October 2010 to August 2014. He was also
the Deputy Permanent Secretary in the same
ministry, responsible for thewater and energy
sectors, a post he held from October 2008.
Kamwendo has been CEO of ZCI Limited
since November 2011 and is a member of
the board of the Copperbelt Development
Foundation, African Copper’s ultimate par
ent company. He has been CEO of several
engineering companies including his own
multi-disciplinary consulting firm.
He has previously chaired the boards
of the Engineering Institution of Zambia,
the Environmental Council of Zambia,
the National Savings and Credit Bank, the
Copperbelt University and ZCI Limited. He
also served on a Presidential Commission
of Enquiry into university education in
Zambia.