Flotation Results
February 21 2006 - 2:02AM
UK Regulatory
RNS Number:6862Y
African Copper PLC
21 February 2006
21 February 2006
www.africancopper.com
AIM: ACU
AFRICAN COPPER Plc
Locked Cycle Flotation Results Improve Recoveries at Dukwe
* Locked cycle flotation results have confirmed the amenability of oxide,
supergene and sulphide ore to recovery within a standard flotation
concentrator.
* Sulphide recoveries of 92% have been achieved at a coarse grind size of
-150 microns producing a marketable concentrate that grades approximately
34% copper, 30% iron and 32% sulphur.
* Supergene recoveries have improved from previous tests with 86% recovery
from a -150 microns grind. A combined oxide-supergene concentrate can be
produced which grades approximately 30% copper, 14% iron and 11% sulphur.
* Preliminary Heavy Media Separation of run-of-mine sulphide material has
shown a promising 84% recovery of copper-bearing minerals with a 7.5% mass
pull. This result may have positive implications for lowering underground
mining costs at the Dukwe Project through the utilization of bulk mining
techniques of the primary sulphide zones.
* Milling characteristics show average work indices - standard crusher/ball
mill configurations are suitable for grinding.
* The flowsheet for a concentrator has been finalized with 3-stage crushing
followed by grinding and a two-stage floatation.
African Copper Plc ("African Copper" or the "Company") announces the following
metallurgical results from the locked-cycle phase of testing on material from
the Dukwe Project in northeastern Botswana. These tests were completed at SGS
Lakefield Labs in Johannesburg and supervised by Senet CC, both independent of
African Copper. These latest tests were designed to check the amenability of
copper recovery to standard flotation techniques. On the basis of these
results, African Copper has finalized the flowsheet for the flotation
concentrator at the project.
Capital and operating costs for the concentrator option were released previously
(see Press Release dated 10 January 2006). Permitting has commenced for the
Dukwe Project, construction of the access road is underway, and the Company has
secured secondary and tertiary crushers.
"These results improve upon the open-cycle tests by improving the copper
recovery and increasing the grade of the concentrates. The concentrates are
clean and of marketable quality. We expect to finalize off-take agreements
shortly", commented David Jones, CEO of African Copper. "We are finalizing
underground mine plans for the extraction of near-surface supergene material and
the subsequent treatment through a concentrator. Supergene material is higher
grade than the deeper primary sulphide mineralization and its early extraction
should enhance the economics for Dukwe."
Bench scale flotation and locked-cycle test results have demonstrated the
amenability of supergene and sulphide ores to recovery within a flotation
concentrator designed to recover both sulphide and oxide copper minerals. The
material can be delivered to the mill as a combined feed with both oxide and
sulphide mineralization treated together through sequential flotation. These
results have been used as the basis for the process selection and forecast
recoveries for the Dukwe Concentrator.
Grinding tests have shown that the supergene and sulphide material at Dukwe is
of average grinding characteristics. Abrasion and Work Indices are shown in the
table below:
Primary Sulphides Industry
Supergene Average
(as per SME Mineral
Processing Handbook)
Bond Abrasion Index 0.67 0.50 0.50
Bond Ball Index 14.5 14.8 14.1
Rod Mill Work Index 13.0 13.1 15.8
The individual recoveries of each type of feed are shown below. In the
supergene tests, the selective leaching of the composite sample showed 26% oxide
copper. The amount of oxide copper in the weathering profile decreases with
depth, and this composite is believed by the Company to represent the average
mill-feed over the first three years of planned mining. These tests were
conducted using a -150 (micro)m grind size. Further test work is underway to
determine whether the grades of the oxide concentrate can be improved.
Weight Assays, % Recovery, %
% Cu Fe S Cu Fe S
Sulphide Composite
Cu Concentrate 4.3 33.7 30.3 32.3 91.9 43.8 53.5
Supergene Composite
Sulphide Cu Concentrate 3.7 42.3 11.4 13.2 63.1 10.7 60.8
Oxide Cu Concentrate 3.4 17.2 15.8 8.5 23.2 13.5 35.6
Combined Cu Concentrate 7.1 30.4 13.5 11.0 86.3 24.2 96.4
Multi-element analyses conducted on the three types of concentrates indicate
that all concentrates fall within acceptable smelter impurity limits for sales
to a smelter.
Heavy liquid separation tests using a media with a specific gravity of 2.96
returned encouraging results. The coarse grained nature of the Dukwe
mineralization results in very few fines produced during crushing and little
copper is lost to slimes in this process. The gangue minerals are essentially
quartz, carbonate and graphite which readily float while the copper bearing
minerals are essentially chalcopyrite and chalcocite which readily report to the
heavy fraction. Preliminary testing on a crush size of 90% passing 1.7mm
resulted in about an 84% recovery of copper to the heavies with a 7.5% mass pull
from a sample of sulphide material that graded 1.47% copper. This result has
positive implications for bulk mining of the deeper sulphide zones since a Dense
Media Separation plant between the crusher and mill may provide a quick,
inexpensive pre-concentration step. Bulk mining of the sulphide zones may
result in lower mining costs, lower development capital and a reduced mining
risk. Further Dense Media Separation studies are planned for the sulphide
mineralization although initial underground mining of the supergene material
will be treated through conventional flotation.
African Copper is a tri-listed (AIM, TSX, Botswana Stock Exchange) international
exploration company. In addition to the Dukwe Project, the Company's other
interests are the 4,000 sq km Matsitama exploration concession adjacent to
Dukwe, which contains two known copper deposits and numerous base metal
exploration targets. A technical report on the Dukwe Project and the Matsitama
concession dated 5 May 2005 and entitled "Technical Report on the Dukwe Copper
Project and Matsitama Prospecting Licences Botswana, Africa" can be found on
SEDAR at www.sedar.com. African Copper has approximately 52 million shares
outstanding.
Mr. Joseph Hamilton, P.Geo., and Chief Operating Officer of African Copper, is a
"qualified person" as defined in Canada by National Instrument 43-101. This
press release has been prepared under Mr. Hamilton's supervision. Mr. Hamilton
has verified the data disclosed in this press release including the sampling,
analytical and test data underlying the information.
- Ends -
This document may contain or refer to forward looking information, including
metallurgical results, mine development plans, and timing of commencement of
operations, and is based on current expectations that involve a number of
business risks and uncertainties. Factors that could cause actual results to
differ materially from any forward looking statement include, but are not
limited to, the metallurgical recovery rates may differ from test results,
failure to establish estimated resources and reserves, the grade and recovery of
ore which is mined varying from estimates, capital and operating costs varying
significantly from estimates, delays in obtaining or failures to obtain required
governmental, environmental or other project approvals, inflation, changes in
exchange rates, fluctuations in commodity prices, delays in the development of
projects and other factors. Forward-looking statements are subject to
significant risks and uncertainties, and other factors that could cause actual
results to differ materially from expected results. Readers should not place
undue reliance on forward-looking statements. These forward-looking statements
are made as of the date hereof and, except as may be required by applicable
securities laws, we assume no responsibility to update them or revise them to
reflect new events or circumstances.
Further information about our properties, to download a copy of our Annual
Report, any technical report, or to access our Press Release Archive please
visit www.sedar.com or our website at www.africancopper.com
For further information contact:
African Copper Plc Numis Securities Limited (NOMAD) Parkgreen Communications
David Jones / Joseph Hamilton John Harrison / James Black Justine Howarth / Ana Ribeiro
+44 (0)20 7321 3721 +44 (0)20 7776 1590 +44 (0)20 7493 3713
This information is provided by RNS
The company news service from the London Stock Exchange
END
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