| Tue 24 Mar 2009, 9:00 | | AEA - African Eagle Resources Plc - Final bottle roll leach test results and |
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AEA
AEA
AEA - African Eagle Resources Plc - Final bottle roll leach test results and
mineralogical analysis from African Eagle`s Dutwa Nickel Project, Tanzania
African Eagle Resources Plc
(Incorporated in England and Wales, registered number 3912362)
JSE share code: AEA JSE ISIN: GB0003394813
AIM share code: AFE AIM ISIN: GB0003394813
FINAL BOTTLE ROLL LEACH TEST RESULTS AND MINERALOGICAL ANALYSIS
FROM AFRICAN EAGLE`S DUTWA NICKEL PROJECT, TANZANIA
High nickel extraction and low acid consumption bodes well for project
* Exceptionally low acid consumption and good nickel recovery confirmed
* High nickel extraction averaging 83% from solids
* Unique laterite mineralogy: high silica, low iron, low magnesium account
for the low acid and high recovery
* Low acid consumption will have a major impact on capital and operating
costs, favouring low cost heap or tank leach processing technology
* Scoping study contract to be awarded
African Eagle Resources plc has received the final results of acid leach tests
and mineralogical analyses on drill samples from its Dutwa nickel laterite
project in Tanzania. The tests were carried out by Mintek in South Africa.
The leach test results show high nickel extractions, averaging 83% on a solid
basis, and very low sulphuric acid consumption, averaging 210 kilograms per
tonne. These compare very favourably with laterite deposits elsewhere in the
world.
The mineralogical analyses show that Dutwa is a unique laterite, dominated by
silica and with very low iron and magnesium. These characteristics account for
the exceptionally low acid consumption and high nickel recovery.
In November 2008, the Company announced a JORC compliant resource at Dutwa of 31
million tonnes at 1.1% nickel and 0.034% cobalt, containing 340,000 tonnes of
nickel and 11,000 tonnes of cobalt.
Mark Parker, African Eagle`s Managing Director comments: "We are delighted with
these results. Dutwa is a unique deposit, with unusual mineralogy which results
in high nickel recovery with exceptionally low acid consumption. This bodes very
well for commercial development, as the ore should be amenable to tank or heap
leaching at atmospheric pressure. Either technology can be implemented at
relatively low capital cost.
"We will now commission a scoping study to assess the viability of the project
and indicate the best way to proceed. We are currently evaluating bids and
expect to award the contract in the next few days. We then expect to commence a
second phase of metallurgical test work to evaluate the heap and tank leaching
nickel-cobalt extraction technology options in greater detail."
Leach tests
The table below shows the total acid consumption and nickel and cobalt
extractions from "bottle roll" leach tests on ten 500g samples, five from
diamond drill cores and five from reverse circulation cuttings. Each sample was
placed in a glass bottle with two litres of dilute sulphuric acid and agitated
continuously by rolling on rotating rollers. Mintek completed the tests in mid-
February 2009 after 82 days rolling. The metal extractions levelled off after 60
days; Mintek notes that similar results from other laterite ores subsequently
gave heap leach cycles of less than 200 days.
Nickel extractions were between 70-90% averaging 83%, based on assays of the
samples prior to the test and of the solid residues at the end of the test.
Extractions calculated from the daily assays of the liquid leachate were higher,
at 80-95%, but are generally less reliable. The acid consumptions, averaging
209kg/t, are very low compared with other nickel laterite ores. The solids-based
cobalt extractions were mostly in the range 70 to 85%.
DH1 DH4 DH6 DH7 DH8 RC25 RC30 RC36 RC55 RC71 Average
Acid 352 196 233 114 200 159 207 304 190 138 209
kg/t
Ni% 85 80 89 78 91 88 71 88 86 75 83
Co% 69 71 77 55 85 76 18 77 86 73 69
See our web site for day-by-day nickel extraction and acid consumption charts:
www.africaneagle.co.uk/african-eagle-projects-dutwa-bottleroll.html
Mineralogy
Mintek used X-ray Diffraction (XRD), and scanning electron microscope (SEM)
backscattered electron images to investigate the mineralogy of the drill core
and chips. Sixteen samples of drill core and five samples of reverse
circulation (RC) cuttings were submitted for XRD analysis. The five RC samples
and five composited drill core samples were investigated by SEM.
The results showed two broad classes of material: a dominant class composed
largely of silica and a mixed class. The latter also contains silica, together
with variable amounts of the iron-chromium oxides magnetite and chromite; the
hydrated iron oxide goethite; "manganese wad", (in which manganese, nickel,
cobalt and other metals replace some of the iron in amorphous goethite); and
small quantities of serpentine and clays.
The silica-rich nature of these samples and their low iron and magnesium
content, indicates that Dutwa is not a typical laterite nickel deposit as the
normal laterite mineralogy is diluted by the high silica. The unusual mineralogy
of the deposit is potentially beneficial, as in heap leaching, the high silica
and low iron should help maintain the structural integrity of the heap and aid
percolation of fluids through the heap, reducing residence times, while in tank
leaching, the high silica should allow good filterability.
In addition, the low iron concentration will result in low impurity levels in
purification steps and potentially, lower capital and operating costs. The lower
iron will also result in commensurately less iron residue for disposal.
Mintek believes that most of the nickel and cobalt occurs in the manganese wad.
The SEM work showed that this can have a manganese content of 20-60%, a nickel
content of up to 20% and a cobalt content of up to 10%. The concentration of
nickel and cobalt in the manganese wad offers possibilities that mechanical
selection of high-grade material may allow reduced throughput and hence a lower
cost processing plant
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/african-eagle-
projects-glossary.html
For further information:
Mark Parker
Managing Director
African Eagle
+44 20 7248 6059
+44 77 5640 6899
Nicola Marrin
Seymour Pierce Limited, London
Nominated Adviser
+ 44 20 7107 8000
Charmane Russell
Russell & Associates, Johannesburg
+ 27 11 8803924
+27 82 8928052
Ed Portman / Gareth Tredway
Conduit PR, London
+44 20 7429 6607
+44 (0) 7733 363 501
About Dutwa
African Eagle has discovered a significant nickel laterite deposit within the
Dutwa project area, which lies in the Kilimafedha belt (Swahili for "money
hills") of the Lake Victoria Goldfield.
Operationally, the project is favourably situated, 100km east of the railhead at
Mwanza and close to the main Mwanza-Nairobi trunk road, a major power line and
the shore of Lake Victoria.
Greenstones and granites underlie the area. The greenstones, of Archaean
Nyanzian age, are mostly metamorphosed volcanic and sedimentary rocks, with some
banded iron formation in the east. Several large ultramafic bodies intrude the
greenstones and the nickel laterites form a blanket up to 60m thick on top of
these.
The Dutwa project area is composed of several prospecting licences covering a
total area of about 750kmSquared. The Company holds 90% interests, with options
to acquire 100%, over most of this ground, including the area of the laterite
discovery, and the remainder is under application.
African Eagle acquired the Dutwa project for its gold potential, but its
exploration team quickly recognised that there was significant nickel laterite
potential. Geochemical soil surveys carried out by African Eagle over the whole
of the project area identified a promising 5km-long nickel anomaly and a number
of gold anomalies. There is very little outcrop, so the Company conducted
extensive ground magnetic surveys to reveal the underlying structure and
geology. The Company has also compiled historical data, including detailed
geological maps and trench results dating from 1956, when rock chip samples from
the trenches over the ultramafic rocks were reported as yielding up to 1.9%
nickel and 10% chromium.
To investigate the nickel anomaly, the Company undertook trial drilling in June
2008. The results were very encouraging and a 139-hole reverse circulation (RC)
drilling programme was completed to delineate the resource. African Eagle also
undertook a 10-hole diamond drill programme to obtain core samples for
metallurgical testing and density measurements.
In November 2008, African Eagle announced an initial Inferred Mineral Resource
estimate of 31 million tonnes at an average grade of 1.1% nickel and 0.034%
cobalt. At a cut-off grade of 0.5% nickel, this gives Dutwa a contained metal
endowment of some 340,000 tonnes of nickel and 11,000 tonnes of cobalt. The
estimate was prepared by independent consultants SRK Consulting (UK) Ltd in line
with the Australasian Code for Reporting of Mineral Resources and Ore Reserves
(the JORC Code). SRK classified the estimate as an Inferred Mineral Resource in
terms of the JORC code, but noted that the deposit is a continuous mineralised
body of simple geometry, which has been well delineated by the drilling, and
could be promoted easily to Indicated category with more density measurements
and improved knowledge of the metallurgy.
The Company despatched 100 kilograms of mineralised drill core and RC chip
samples to Mintek Laboratories in Johannesburg for investigations into the
mineralogy and metallurgy of the deposit, especially tests of the amenability of
the material to sulphuric acid leaching. Mintek carried out mineralogical
characterisation by X-ray diffraction (XRD), scanning electron microscopy (SEM)
and polished section work, to determine the nature of the ore body, and extended
`bottle roll` acid leach tests on ten samples, to investigate metal recoveries
and acid consumption.
The bottle roll test results show nickel extractions of 70-90% with an average
of 83%, based on assays of the samples prior to the test and of the solid
residues at the end of the test. Cobalt extractions were mostly in the range 70
to 85%. The acid consumptions, averaging 209kg/t, are very low compared to other
nickel laterite ores worldwide.
The mineralogical investigations show that the laterite is extremely silica-
rich, with low iron and magnesium content, indicating that Dutwa is not a
typical laterite nickel deposit. Mintek believes that much of the nickel and
cobalt occurs in "wad" with manganese content of 20-60%, nickel content of up to
20% and cobalt content of up to 10%.
The unusual mineralogy of the deposit is beneficial, as the low iron
concentration will result not only in lower acid consumption, but also in
commensurately less iron residue for disposal. In a heap leach, the low iron and
high silica should help maintain the structural integrity of the heap and aid
percolation of fluids through the heap, reducing residence times. The
concentration of nickel and cobalt in the manganese wad offers possibilities
that mechanical selection of high-grade material may allow reduced throughput
and hence a lower cost processing plant.
As the next step in the process, African Eagle is commissioning a Scoping Study
to investigate the key operating parameters and to assess the economic potential
of the project.
The Company has also completed a trial programme of RC drilling to test a
laterite at its Zanzui project, 70km to the south of Dutwa. Results included
42m at 1.05% nickel (including 6m at 2.80%) and 33m at 0.91% nickel (including
9m at 1.41%).
About African Eagle
African Eagle is a diversified mineral exploration and development company
operating in eastern and central Africa. The Company`s principal advanced
projects are the Dutwa nickel laterite discovery in Tanzania, where the Company
announced a significant resource at the end of 2008, and the Mkushi Copper Mines
project in Zambia, for which a draft Feasibility Study was completed in Q4 2008.
African Eagle has also defined a gold resource estimated at half a million
ounces at the Miyabi gold project in Tanzania, and is evaluating a second
promising nickel laterite deposit which it recently discovered in Tanzania. The
Company holds a well-balanced portfolio of promising earlier stage gold and base
metal projects, including the Ndola and Mokambo projects in the Zambian
Copperbelt.
Zambia, Tanzania and Mozambique, the sites of African Eagle`s projects, are all
countries which have highly prospective geology, relatively low above-ground
risks and track records of successful major investments in the metals and
minerals industries.
African Eagle specialises in project generation and exploration. To take its
discoveries into production, it seeks to sign up industry partners with records
of successful mine development. These joint ventures and, in time, the revenue
from advanced projects, will finance future exploration and new discoveries.
24 March 2009
Sponsor
Nedbank Capital
Date: 24/03/2009 09:00:03 Produced by the JSE SENS Department.
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