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  • Deep Yellow Confirms Heap Leach Option For Omahola Uranium 0 comments
    Apr 3, 2013 11:31 PM

    Deep Yellow (ASX: DYL) has completed initial metallurgical testwork that has demonstrated the potential for a heap leach operation at its flagship Omahola Uranium Project in Namibia.

    Heap leach processing has the potential to reduce cut-off grade, with a corresponding increase in overall uranium extraction whilst reducing project capital costs and accelerating the likely development schedule at Omahola.

    "We are pleased with this initial result which has demonstrated that heap leach is a realistic option for Omahola," managing director Greg Cochran said.

    "We acknowledge that there is still much work to do, however this gives us the confidence to plan a trade-off study to compare the options to see which process route delivers the best economic outcome.

    "It is noteworthy to see the substantial increase in the resource base using a lower cut-off grade, which provides us with additional optionality around project development given the existing high grade areas of the resource."


    The column leach test, conducted at Gecko Laboratories in Swakopmund, Namibia, was on a composite of samples collected from seven diamond drill holes located across the Ongolo and MS7 alaskite deposits.

    These results were compared against conventional laboratory bottle roll and beaker agitation leach tests which are used to determine theoretical maximum uranium extraction.

    The aggressive leach conditions used in the glass beaker and bottle roll techniques gave an average extraction of 89.7% and an average acid consumption rate of 59.5 kilograms of H2SO4 per tonne.

    Deep Yellow noted the high acid consumption was expected as the samples were milled to 100% passing 75 μm.

    In comparison, the column leach process resulted in a recovery of 80.3% after 7 days and 80.6% after rinsing though the resulting increase in flux to 0.71 square metres per tonne following rinsing with water from 0.34 square metres prior was not considered worthwhile.

    Overall acid consumption during this process was 12.4 kilograms of H2SO4 per tonne.

    Notably, the observed slump after completion of the column test was 30 millimetres, or 4.5%, which is considered to be low while the leach effluent liquor from the column was clear with no suspended solids observed.

    This makes it ideal for the solvent extraction process as no crud formation was evident.

    Assuming the results are confirmed, reducing the cut-off grade and therefore average grade of the resource could increase contained and ultimately recoverable uranium up to 298 million tonnes at 191ppm U3O8 for a contained resource of 125 million pounds of U3O8 at the 100ppm cut-off.

    A trade-off study is being planned to compare heap leach against tank leach at Omahola to see which delivers the best economic outcome.

    There are numerous scenarios that need to be taken into account and it is hoped that there is an opportunity to capture some of the resource upside associated with a heap leach processing option by using a lower cut-off grade whilst still accessing the existing high grade areas of the resource.

    Picture: Uranium recovery from column leach test


    Omahola currently holds a JORC resource of 48.7 million tonnes at 420ppm U3O8 for a contained resource of 45.1 million pounds of U3O8 at the 250ppm cut-off.

    The last independently held alaskite project in Namibia, Omahola consists of a number of deposits including Ongolo, INCA and the high grade MS7 deposit.

    Ongolo mineralisation - primarily uraninite - comes to within 20 metres of surface and underlies a broad, flat gently sloping sheetwash plain, thinly veneered by gravelly alluvial and aeolian sands.

    MS7 is a mineralised zone of about 600 metres along strike and up to 400 metres wide about 2 kilometres west of Ongolo while INCA hosts unique high grade uranium, magnetite and pyrite mineralisation.

    These will all feed into a mine that Deep Yellow envisions as capable of producing at least 2.2 million pounds of U3O8 from 2016 from a processing plant located close to the Ongolo Alaskite deposit.

    Interim Pre-Feasibility results released in 2011 based on the INCA and Tubas Sand deposits had demonstrated the potential for an operation with competitive capital costs of less than US$340 million and operating costs of around US$32 per pound of U3O8.

    Omahola is located within Namibia's 'Alaskite Alley', which includes the Rossing uranium mine and Husab uranium project. Structures along this trend are associated with higher grade alaskites.

    Due to the proximity of the project to the coastal towns of Swakopmund and Walvis Bay and ready access via a sealed, black-top road there will be no need for on-site housing for construction and operation personnel.


    The testwork showing that development of Omahola is feasible using heap leach processing has the potential to reduce capital while offering more flexibility in bringing the project into production.

    This is further reinforced by the growing resource base that will provide the critical mass and tonnage needed.

    Deep Yellow is well funded with $7.2 million in cash as of the end of December 2012 quarter.

    Proactive Investors Australia is the market leader in producing news, articles and research reports on ASX "Small and Mid-cap" stocks with distribution in Australia, UK, North America and Hong Kong / China.

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