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AEA - African Eagle Resources plc - Results of Leaching Test Work on the Dutwa
Nickel Project, Tanzania
African Eagle Resources plc
Incorporated in England and Wales
(Registration number 3912362)
(AIM share code: AFE AIM ISIN: GB0003394813)
(JSE share code: AEA JSE ISIN: GB0003394813)
Results of Leaching Test Work on the Dutwa Nickel Project, Tanzania
African Eagle Resources plc (AIM: AFE; AltX: AEA) is pleased to announce
positive results from extensive hydrometallurgical test work performed on
representative ore samples from its flagship Dutwa Nickel project in Tanzania.
The test work, using tank acid leaching at atmospheric pressure conditions,
confirmed the recovery of nickel from each of the principal Dutwa ore types and
demonstrates that an integrated two-stage leach process achieves improved metal
extraction with reduced reagent demand.
On the basis of these favourable results, the Company and its design engineer
Lycopodium are developing the preliminary Dutwa process flow sheet. The
preliminary flow sheet will be modelled in the pilot plant test programme,
scheduled to commence in the second quarter, which will result in the
confirmation of the optimal final process flow sheet and plant design for the
project, which will be reflected in the BFS. The pilot plant programme will be
performed at the SGS Lakefield Oretest laboratory in Perth, Australia and will
process approximately 50 tonnes of ore.
Key results:
Efficient and consistent nickel extraction by atmospheric pressure tank acid
leach confirmed
Low acid consumption of Wamangola ore (350 to 450 kg/t) reaffirmed
Rapid leach kinetics confirmed
Chemistry of principal ore types validated
Early test work on two-stage leaching achieves improved nickel extraction over
single ore type processing with reduced reagent consumption
Preliminary process flow sheet being developed with study engineer, Lycopodium
Pilot-scale tests scheduled to begin Q2
Drilling to obtain representative bulk ore samples underway
African Eagle`s CEO Trevor Moss said "These test work results continue to be
very encouraging and reconfirm that Dutwa`s unusual nickel laterite mineralogy
is amenable to proven atmospheric leach technology, which is in operation at
First Quantum`s Ravensthorpe mine in Western Australia. The final step of our
systematic metallurgical programme, to commence shortly, will demonstrate the
Dutwa flow sheet through the pilot plant in order to confirm the final process
selection and plant design for the BFS."
Since the completion of the scoping study update in February 2011 the Company
has been undertaking systematic and detailed metallurgical bench-scale test work
at laboratories in Perth, Western Australia, to evaluate the suitability of
various atmospheric leach processes for treating Dutwa ores. The principal
outcome of this work was the selection of atmospheric tank leaching as the
preferred treatment process, as announced earlier this year.
This test work programme has been conducted on bulk ore samples extracted from
the Dutwa deposits by a targeted diamond drilling campaign and were designed to
confirm the initial favourable metallurgical characteristics observed in the
scoping study analyses, and to assess the variability of the ore types which are
found at Wamangola and Ngasamo.
The hydrometallurgical tank leach test work was undertaken by ALS Ammtec at its
laboratory in Perth, Western Australia. Standardised atmospheric batch leach
tests were performed on ground whole ore composites for each of the principal
ores to investigate how the recovery of nickel varies with leaching time and
sulphuric acid addition. The first phase of test work comprised a total of 28
tests.
Each composite, weighing approximately 0.5 tonnes, was created from sections of
diamond drill core carefully selected to ensure they were representative of each
ore type. The diamond drill hole locations were themselves chosen to be
spatially representative of the planned pit shells for each of the two deposits,
Wamangola and Ngasamo. The predominant ore types at Dutwa have been labelled
Ferruginous Siliceous ("FeSi") and Transitional.
The chemical analyses of elements of interest in the five composites by X-ray
fluorescence (XRF) are:
Sample %Ni %Co %Fe %Al %Mg %Mn %Cr %Si
Wamangola -FeSi 1.0 0.05 7.8 1.0 1.2 0.18 0.49 36.7
Wamangola 1.93 0.06 8.9 0.89 4.9 0.19 0.50 31.7
-Transition 1
Wamangola 1.33 0.02 8.5 0.61 8.2 0.13 0.36 29.4
-Transition 2
Ngasamo -FeSi 0.97 0.05 8.5 0.91 3.2 0.18 0.38 34.1
Ngasamo - 0.96 0.02 6.9 0.36 9.2 0.12 0.45 28.3
Transition
The compositions of the bulk samples are in good agreement with the average
compositions of mine grade material estimated from the deposit modelling by
Snowden, reported on 11 January 2011, other than Wamangola Transition 1, which
is a low magnesium variant with higher nickel content than the resource average
for Wamangola transition ore. For this reason, a second Wamangola transition
composite was created. Tests on this second composite have commenced.
All the bench-scale tank leach tests employed conservative conditions, such as a
relatively coarse grind size (100% passing 212 micron), and an initial solids
content of 30% w/w in the leach feed. The ores were prepared in potable water
for consistency with the expected water quality at Dutwa. The leach temperature
was 95oC and the leach duration was either 8 or 12 hours. Concentrated
sulphuric acid (98%) was added at the start of the leach as the lixiviant.
Typical final results from the individual ore samples, after 12 hours leaching
at 95oC were:
Test Sample * Acid Terminal % Ni Acid
ID Addition Free Acid Recovered consumed
(kg/t ore) (g/L) t/t Ni
recovered
HY385 WM - FeSi 350 53 78.0 45.8
HY449 WM - FeSi 401 66 82.9 49.4
HY386 WM- Trans1 425 35 83.5 26.2
HY450 WM- Trans1 451 38 86.0 27.6
HY638 WM- Trans1 500 45 89.7 27.8
HY387 NG - FeSi 376 46 73.0 51.8
HY451 NG - FeSi 415 52 74.9 56.8
HY388 NG - Trans 526 28 76.1 71.1
HY452 NG - Trans 550 35 81.1 71.3
HY637 NG - Trans 625 52 85.5 77.6
Note: * WM denotes Wamangola and NG denotes Ngasamo
Acid consumptions for the major "FeSi" ore type at Dutwa ranged from 350 to 415
kg/t ore, and across all samples from 350 to 625 kg/t ore. These results
compare favourably with reported values for many Western Australian and South
American laterites, which range from 500 to 700 kg/t. Acid consumption is
mostly at the lower end of expected ranges for atmospheric leaching of nickel
laterite ores. As seen in previous tests, the leaching progressed rapidly.
Example results for recovery versus time are:
Time HY449 HY450 HY451 HY452
(hrs) (WM FeSi) (WM Trans1) (NG FeSi) (NG Trans)
Ni % Acid Ni % Acid Ni % Acid Ni % Acid
rec. g/L rec. g/L rec. g/L rec. g/L
2 58.7 107 78.2 66 56.9 93 74.8 60
4 74.3 87 82.0 55 66.9 75 77.4 50
6 78.2 78 83.1 48 70.0 64 79.4 44
8 80.1 74 84.3 46 70.1 60 78.6 38
10 81.0 69 84.9 44 73.1 58 80.3 38
12 82.9 63 85.7 41 74.9 56 81.1 37
The results demonstrate that both "FeSi" and Transitional ores are amenable to
atmospheric tank leaching using sulphuric acid, with nickel recoveries generally
exceeding 70% after 4 hours and around 80% or higher after only 8 hours. With
the use of leaching times longer than 12 hours, it is considered that the
ultimate nickel recoveries may be higher than those reported. Further test work
with leach times of up to 24 hours is being undertaken by African Eagle to
confirm this. The Wamangola ores exhibit about 15% lower acid consumption than
those from Ngasamo due to their lower magnesium content, and nickel leaches from
Wamangola "FeSi" ore somewhat faster than from equivalent Ngasamo ore.
Transitional ore has faster initial leaching rates than "FeSi", which is
attributed to a greater proportion of the nickel being hosted in clay and
serpentine minerals rather than goethite.
African Eagle also tested an integrated leaching process, with "FeSi" ore in an
initial leach stage and transitional ore added in a second stage, to assess the
viability of processing both Dutwa ore types in a single leach circuit. The
tests were performed at 95oC, typically for 16 hours. The test parameters
examined included the ratio of "FeSi" to Transitional ore, consistent with the
Dutwa deposit and mining models, and total acid addition. Transitional ore is a
significant component of the Ngasamo deposit.
Example results from a selection of these tests are tabulated below:
Test Deposit/O FeSi:Trans Acid Termina Overall % Acid
ID re Ratio (w/w) Additio l Ni consumed
n Free Recovered t/t Ni
(kg/t Acid recovered
ore) (g/L)
HY548 Wamangola 2.8 313 30 74.0 34.3
HY476 Wamangola 2.8 350 37 78.6 36.3
HY596 Wamangola 2.8 380 41 80.6 38.2
HY477 Wamangola 2.8 405 48 84.2 38.6
HY468 Wamangola 2.9 450 67 87.4 41.1
HY567 Ngasamo 1.5 390 11 70.1 55.9
HY547 Ngasamo 1.5 450 26 77.3 58.7
HY591 Ngasamo 1.5 450 24 75.9 58.6
HY494 Ngasamo 1.5 464 40 80.9 57.8
HY623 Ngasamo 2.0 500 40 81.2 61.7
HY473* Ngasamo 1.5 600 75 85.8 72.2
* 12 hour test
The results of these tests suggest that a two-stage leaching process could be
used to treat "FeSi" and Transitional ores, in the same proportions by mass as
they occur in the Dutwa deposits. Good overall nickel recoveries (ranging from
81% to 87%) were achieved from Wamangola ore, with sulphuric acid additions of
350 to 450 kg/t ore, equating to acid consumptions of only 38 to 41 tonne of
acid per tonne of nickel recovered. Due to their chemistry and mineralogy, the
Ngasamo ores required 50 to 100 kg acid/t ore more than Wamangola ores to obtain
nickel recoveries above 80%.
Lower acid and iron concentrations were observed in the final leach solutions
from these tests. Two-stage leaching is anticipated to offer benefits such as
lower overall acid consumption and reduced reagent demands compared to leaching
of individual ore types alone. Additional testing is being undertaken to
develop and optimise the Dutwa leach process further.
About Dutwa
Dutwa was discovered in 2008 and has a JORC resource of 99 million tonnes at
0.93% Ni. The project is a nickel laterite project with unusually beneficial
geometallurgical properties, which makes it amenable to straightforward
atmospheric acid leaching with comparatively low acid consumption. This
combined with ready mining from two hilltop deposits leads to strong project
economics. A Bankable Feasibility Study is currently underway and due around
the end of 2012.
About African Eagle
African Eagle Resources plc is a junior mining explorer and developer with
development projects in Tanzania and Zambia. The Company`s flagship project is
the Dutwa Nickel project in Tanzania located about 25km south of Lake Victoria
and 110km east of Mwanza within greenstone gold belts which host many of
Tanzania`s operating and developing gold mines. The Company is quoted on the
AIM market of the London Stock Exchange (AIM: AFE) and on the AltX of the
Johannesburg Stock Exchange (AltX: AEA).
Technical terms
A glossary of technical terms used by African Eagle in this announcement and
other published material may be found at www.africaneagle.co.uk/p/glossary.asp.
Qualified Person
Information in this report relating to metallurgical test results is based on
data reviewed by Chad Czerny PhD, Project Manager - Metallurgy for African Eagle
Resources, who is a Member of the Australasian Institute of Mining and
Metallurgy, has more than 20 years` relevant experience in the mining and
metallurgical industry, and is a Qualified Person under AIM guidelines. Dr
Czerny consents to the inclusion of the information in the form and context in
which it appears.
Sponsor
Merchantec Capital
20 March 2012
For further information:
Please visit the Company`s website: www.africaneagle.co.uk or contact:
African Eagle Resources plc
Trevor A. Moss (CEO)
Chad Czerny (Project Manager - Metallurgy)
Yasumi Toyoda (Investor Relations)
+44 20 7248 6059
Canaccord Genuity Limited
Rob Collins
Andrew Chubb
+ 44 207 050 6500
Ocean Equities Limited
Guy Wilkes+44 20 7786 4370
Russell & Associates, Johannesburg
Charmane Russell
Marion Brower+27 11 8803924
Date: 20/03/2012 09:00:06 Supplied by www.sharenet.co.za
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