African Eagle Resources (AIM: AFE) has reported exceptional results from column leach tests for the Dutwa nickel project in Tanzania. The company said the result opens a wider range of leach options, by either heap leaching or tank leaching at normal atmospheric pressure.

According to African Eagle the leach tests, using 1m columns, performed exceptionally well achieving good nickel and cobalt recovery whilst maintaining low acid consumption. The results showed nickel extraction of 73-82% within 30 days and 86-92% after 100 days, while cobalt extraction reached up to 60% within 30 days and 80-85% after 100 days. Tank leach tests gave 80-85% nickel extraction within 8 hours

"We are delighted with the results of our phase 2 column and tank leach tests, which show that Dutwa ore could be processed by either heap leaching or tank leaching at normal atmospheric pressure, without recourse to the high cost and hi-tech complications of high pressure acid leach (HPAL)”, African Eagle MD Mark Parker commented.

"The leaching reaction proceeds very quickly, especially for the first two-thirds of the contained nickel, and the acid consumption is much lower that for comparable deposits elsewhere. This opens a wider range of leach options and, if heap leaching is used, implies that working capital should not be tied-up for a long period while the heap reaches full productivity."

The leach tests were performed by Mintek Laboratories in South Africa, on 250kg of sample taken from seven drill cores from the main Dutwa nickel deposit. Mintek carried out column and tank leach tests, preliminary agglomeration tests and preliminary ore characterisation tests. This second phase of metallurgical testwork was carried out as part of African Eagle's pre-feasibility study on Dutwa.

Column leach tests were performed to obtain information on the likely behaviour of the ore in the heap leaching process.

According to Afican Eagle, the initial leaching was extremely fast with 60-65% of the nickel being extracted within two weeks. Subsequently, the rate of leaching slowed reaching 73-82% after one month, and 90-94% over the full five month test. The acid consumed to achieve these extractions was low, averaging 199, 273 and 360 kg/tonne respectively.

“Clearly, more than half of the nickel in Dutwa ore is contained in a readily leachable mineral phase”, the company stated.

Furthermore, the company noted highlighted that the fast initial leaching is especially encouraging, with the extraction of 65% of the contained nickel in two weeks acid meaning that working capital will not be tied up for a long period while the heap reaches full productivity. “Such a short leach cycle extends the heap engineering options and offers the potential to use dynamic heaps”.

Also, five tank leach tests were performed at 90°C and atmospheric pressure. African Eagle noted that in all five tests, the reaction was very fast and most of the nickel leaching within the first hour. Nickel extraction of up to 70% occurred in the first hour, with up to 85% after 8hrs and final nickel extractions averaging 94% over the full 24hr test.

The company also confirmed that a geochemical domain model of the Dutwa deposit has been completed, and it will be used to design a programme of bulk sampling which will provide a large representative ore sample for the next phase of metallurgical testwork.

The next phase will include large scale column tests, mineralogical analyses, beneficiation tests, and further tank leach and agglomeration tests. African Eagle said that the results of the planned work will develop further the optimum processing route for Dutwa ore.

Earlier this month, African Eagle received the last batch of assay results from the recently completed drilling at Ngasamo Hill, a part of the Dutwa project. The assays were sent to Snowden Mining Industry Consultants in Perth for a formal resource estimate.
"We are extremely pleased with the drill results from Ngasamo. They reveal a deposit which is somewhat thicker than the main Dutwa deposit, and although the average grade appears to be slightly lower, we expect Ngasamo will add significantly to the overall resource base”, Mark Parker stated.

Of the 66 holes drilled in the vertical reverse circulation (RC) programme which was designed to delineate a formal Mineral Resource to JORC Inferred category or better, 59 intersected mineralisation, and highlights include: 75 metres at 1.42 percent nickel, 84 metres at 1.07 percent nickel including 30 metres at 1.64 percent, 63 metres at 1.41 percent nickel including 45 metres at 1.71 percent, and 57 metres at 1.25 percent nickel including 12 metres at 2.48 percent.

Key cobalt mineralisation intersections include 18 metres at 0.47 percent cobalt, 9 metres at 0.43 percent and 9 metres at 0.27 percent cobalt, the latter including 3 metres at 0.48 percent.

African Eagle has also completed an infill drilling programme at the Dutwa main deposit, designed to test the internal variability of the mineralisation and allow the Dutwa main resource to be upgraded to JORC Indicated category.

With  the  determination  of  a  resource  estimate  at Ngasamo to JORC inferred standard or better,  African Eagle  will have  completed its  earn-in of a 35 percent interest in the deposit from Ngasamo's owners, Safina a.s. of the Czech Republic and  its Tanzanian subsidiary Precious Metals Refinery Company Ltd.  Thereafter, the company can increase its equity in Ngasamo to at least 50 percent and up to 75 percent by completing further resource and feasibility work.

Since discovering major oxide nickel deposits at Dutwa, African Eagle is in transition from a diversified explorer into a nickel mining company. The company completed a positive scoping study on the Dutwa deposit in July 2009 and is now working towards a full feasibility study.

African Eagle is evaluating a second promising oxide nickel deposit at Zanzui in Tanzania, 60 kilometres south of Dutwa.

The company also holds a 49 percent interest in the Mkushi Copper Mines joint venture in Zambia, for which a draft feasibility study was completed in Q4 2008.

In addition, it holds a half million ounce gold resource at the Miyabi project in Tanzania. On the 14th May, African Eagle announced a joint venture deal with Macquarie Harbour Mining Ltd (ASX: MHM). Under the agreement, MHM will provide all the technical expertise and funding for a feasibility study sufficient to enable MHM to make a decision to develop a mining operation at Miyabi.  African Eagle will retain 25 percent of its interest in the project and its past exploration expenditure will be credited against the development costs.

“This transaction provides a quick and effective route to take Miyabi into production, fully crediting African Eagle's past exploration expenditures against the costs of developing the mine, which we believe will amount to a free-carry into production”.

The company also has a portfolio of gold and base metal exploration assets, including two projects in the Zambian Copperbelt.

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