16
MODERN MINING
July 2014
MINING News
Blackthorn Resources, listed on the ASX,
has provided an update on activities at its
100 %-owned Mumbwa project in Zambia
that hosts the flagship Kitumba deposit, as
well as other prospective targets, including
the Kakozhi prospect. Mumbwa is located
200 km west of Lusaka.
The company recently announced the
results of the Optimised Prefeasibility
Study (OPFS) for the Kitumba copper
project. This significantly enhanced the
project’s economics and development
potential and Blackthorn confirmed that
it would progress to a Definitive Feasibility
Study (DFS).
As outlined in the OPFS, it is proposed to
Mumbwa drilling campaign will support DFS studies
develop Kitumba as an underground mine.
A 3 Mt/a production rate at a stope design
cut-off grade of 1,0% copper was chosen as
the preferred mining production rate. This
results in a production mine life of 11 years,
producing an average of 58 000 tonnes of
contained copper in ore per annum.
The mined ore will be processed via a
concentrator that includes conventional
comminution and flotation to produce
a sulphide rougher concentrate and a
rougher tail containing the non-flotable
copper. The sulphide concentrate will be
treated through a pressure oxidation (POX)
leach. The POX process produces acid and
ferric iron as part of the process. This will
be used to leach the copper in the flota-
tion tails in an atmospheric leach circuit.
The resulting copper-rich solution will be
fed to a conventional solvent extraction
and electrowinning (SX/EW) plant.
Prior to engaging a study manager for
the DFS, Blackthorn says it will be conduct-
ing a comprehensive drilling campaign of
approximately 12 000 m in and around the
Kitumba mineral resource to aid in the DFS
level studies for both the proposed mine
and process plant design.
The Kitumba mineable reserve contains
a range of primary and secondary copper
minerals, with varying copper grade and
mineralogy. The drilling for the collection
of metallurgical samples has therefore
been designed with this in mind, to ensure
that the right type and volume of sam-
ples are collected to enable the impact
of orebody variability to be appropriately
assessed by the test-work programme.
Variability test work on a range of ore
blends representing the changing spatial
distribution of minerals throughout the
deposit is planned to provide data on
the range of metallurgical performance
expected for the proposed flow sheet.
The geotechnical drilling requirements
for the DFS-level assessment are based on
the revised sub-level caving mine design
presented in the OPFS. The DFS geotech-
nical drilling programme is mainly based
on targeting the box cut, development
drives and shafts, and cave areas lacking
sufficient coverage from previous drilling.
The drilling plan for hydrogeological
assessment has been prepared to collect
sufficient data for a DFS-level assessment
of both the mine dewatering requirements
as well as to confirm water supply sources
for the operation.
Cullinan delivers another exceptional stone
Petra Diamonds recently recovered an
exceptional 122,52 carat blue diamond at
the Cullinan mine in South Africa. The stone
will require further analysis in order to assess
its potential value and, upon completion of
this process, Petra will be in a position to
evaluate its optimal route to market.
According to Petra, the rarity of a blue
diamond of this magnitude sets it apart as
a truly significant find. Cullinan is known as
the world’s most important source of blue
diamonds and, since Petra acquired the
mine in 2008, it has continued to produce
a number of exceptional blues.
Located in the foothills of the Maga
liesberg mountain range, 37 km north-east
of Pretoria, Cullinan is one of the world’s
most celebrated diamond mines. It earned
its place in history with the discovery of the
Cullinan diamond in 1905, the largest rough
gem diamond ever found at 3 106 carats.
Over its more than 100-year life it has pro-
duced over 750 stones weighing more than
100 carats, 130 stones weighing more than
200 carats, and around a quarter of all dia-
monds weighing more than 400 carats.
Petra CEO Johan Dippenaar holds the 122,52 carat
blue diamond recovered in June 2014 at Cullinan
(photo: Petra Diamonds).
