Test Results - Dikoloti

AIM RELEASE 12th November 2007 * Successful new nickel recovery tests for the Dikoloti Nickel Project in North-east Botswana * Snowden to prepare new scoping study financial model for project Discovery Metals Limited (AIM: "DME") has completed a comprehensive new study into the most cost effective way to process ore from its Dikoloti nickel deposit in north-east Botswana, using a state-of-the-art heap leach bio-oxidation process. The study was based on GeoBiotics LLC's proprietary GEOLEACHTM process, which has been developed as a method to recover base metals from sulphide ores as an alternative to stirred tank leaching and other competing technologies. Following the positive results of the study, Discovery has contracted Snowden Mining Industry Consultants to revise the Dikoloti scoping study financial model as the bio-oxidation process has the potential to lower capital and operating costs for development of the project, in comparison to traditional flotation processing techniques. Highlights from new metallurgical test work * The Dikoloti nickel mineralisation is amenable to heap leach bio-oxidation processing using the GEOLEACHTM process; * Greater than 74% nickel extraction from the ore was achieved after 160 days; * 99% of the extracted nickel can be recovered from the bio-oxidation solution as a nickel sulphide, by use of sodium sulphide precipitation; * The heap leach approach using GEOLEACHTM should have capital and operating costs which are significantly lower than conventional flotation processing. Discovery Metals' Managing Director, Mr Jeremy Read, said today that the metallurgical test work using the GEOLEACHTM process had shown that bio-oxidation was a technically feasible method for processing the Dikoloti nickel-copper mineralisation. "The positive results from the GEOLEACHTM bio-oxidation test work are a big step forward for the project. We have now identified a processing technique which could lead to Dikoloti being developed as a stand-alone operation," Mr Read said. "We are currently having the scoping study financial model for Dikoloti revised, based upon a bio-oxidation heap leap operation. Once the results of this financial review are known, we will make a final decision on how to progress Dikoloti to the next project development phase," he said. Dikoloti Mineral Resources The Dikoloti mineral resource is situated 12km from Africa's largest nickel processing facility at Selebi-Phikwe in NE Botswana. The Dikoloti resource is currently 4.1 million tonnes at 0.7% nickel, 0.5% copper and 1.2 grams per tonne of Platinum Group Elements at a cut-off of 0.5% nickel and has been classified as Inferred under the guidelines of the 2004 JORC Code. Dikoloti Bio-Oxidation Metallurgical Test Previous testing by Discovery Metals on the Dikoloti nickel mineralisation indicated that a costly fine grind would be required in order to liberate the nickel at acceptable recoveries using traditional flotation processing techniques. Consequently, the Company evaluated several alternative methods for processing the nickel mineralisation and determined that the technique with the most promise was bio-oxidation heap leaching using the GEOLEACHTM process developed by GeoBiotics LLC from Lakewood, Colorado. Discovery contracted GeoBiotics to conduct scoping study tests in order to determine if the GEOLEACHTM process was a viable process route for the Dikoloti nickel-copper mineralisation and would allow Dikoloti to be developed as a stand-alone operation. The scoping study test has recently been concluded. The initial results from the test work were reported on 31st August, 2007. Discovery provided to GeoBiotics a 55kg sample of representative nickel-copper mineralisation from Dikoloti. A 2kg sample of this material was crushed and used for the bacterial amenability test, while the remainder of the sample was crushed, screened and used for 2m column tests. The representative samples assayed 0.64% Ni, 31.2% Fe and 11.4% Si. The test procedure comprised the following: 1. Acid consumption test 2. Bacterial Amenability Test (BAT) 3. 2m column test simulating the conditions of a heap 4. Nickel sulphide recovery test Acid Consumption Test Prior to column testing, an acid consumption test was conducted on a pulverised sample to determine the maximum acid consumption expected from the material. The observed acid consumption was 385 kg/t after 60 days. The high acid usage was largely due to the acid consumption of the pyrrhotite component of the ore sample. It was expected that the acid consumption of the ore in the column test would be lower than this value. Bacterial Amenability Test The Bacterial Amenability Test (BAT) investigated the ability of the bacterial culture to break down the nickel-copper mineralisation and release the nickel and copper in to solution. The BAT was carried out in a stirred tank using an adapted thermophile bacterial culture on a pulverised ore sample. The optimum pH value for bacterial culture growth is generally between 1.4 and 1.8 and therefore acid is added to the system for the BAT. In addition the system needs to operate under high oxidising conditions (Eh levels above 500 mV) for adequate mineral oxidation and release of the nickel and copper in solution to take place. The BAT showed that nickel rapidly leached out of the mineral within a period of 10 days and that rapid leaching was achieved using a thermophile bacterial regime. Based upon solution analysis 98% of the nickel was extracted after 10 days. Column Test A GEOLEACHTM 2m column test on whole Dikoloti nickel-copper ore was conducted over a period of 160 days in order to simulate the processes which would occur within a heap leach operation. The initial part of the test was a simple acid leach to evaluate acid consumption and this test indicated that pyrrhotite consumed a significant amount of acid with a subsequent rapid release of iron into solution. The column was initially started with thermophile bacteria which generally operate at a higher temperate, but was re-inoculated with mesophile bacteria (which operate in the temperate range 30-45oC) at day 42. Between days 42 and 66 it became apparent that due to the rapid build up of iron in the column, as the pyrrhotite was broken down, the bacteria in the column lacked the capacity to convert the rapidly increasing ferrous iron in the column to ferric iron. After 70 days of operation, a separate bacterial ferric generator column was instituted with the aim of providing externally additional culture and surface area for converting the ferrous iron, being produced from the leaching of pyrrhotite, to ferric iron in order to allow the oxidation of the nickel mineralisation and subsequent release of nickel in to solution. After 120 days a fully active 2m ferric generator column was used and connected directly to the 2m leach column in order to provide more surface area and residence for bacteria culture growth. This increased the ability of the entire system to convert ferrous iron to ferric iron as needed in order to liberate the nickel. Following the installation of the separate bacterial ferric generator column iron and nickel leach rates significantly increased. After running the column for 150 days the maximum nickel extraction was estimated to be 75% and the maximum iron extraction 50%. The net acid consumed to achieve these extractions was 300 kg/t. Therefore, given that both the BAT and column tests demonstrated that nickel extraction is achievable, the economic viability of the project will be largely determined by the acid consumption. Nickel Sulphide Recovery Test A procedure was developed for the precipitation of nickel as nickel sulphide from the fluid generated from the column test. Sodium sulphide was used as the reactant and 99% of the nickel in solution was precipitated as nickel sulphide. Conclusions The conclusions from the bacterial amenability tests and the GEOLEACHTM 2m column test are: * The Dikoloti nickel-copper ore is amenable to bio-oxidation * Nickel extraction indicates that at least 74% of nickel can be extracted * The fundamental challenge for the successful bio-oxidation of the Dikoloti nickel mineralisation was the high iron levels in the solution and managing the conversion of ferrous to ferric iron. * The use of a separate ferric generator column coupled to the leach column was successful with the required ferrous to ferric iron conversion * The acid consumption of the Dikoloti mineralisation was high due to the predominance of pyrrhotite in the mineralisation * It is possible to successfully recover 99% of the nickel from the bio-oxidation solution as nickel sulphide by using sodium sulphide precipitation. Following the successful conclusion to the scoping bio-oxidation tests Discovery has contracted Snowden Mining Industry Consultants to revise the scoping study economic model for Dikoloti, based upon a heap leach bio-oxidation processing scenario. Further information on the Company is available on its website: www.discoverymetals.com.au The information in this report as it relates to Mineral Resources was compiled by Mr. Stefan Mujdrica, who is a Member of The Australasian Institute of Mining and Metallurgy. Mr Mujdrica is a full time employee of Snowden Mining Industry Consultants. Mr Mujdrica has sufficient experience which is relevant to the style of mineralisation and type of deposit under consideration and to the activity which he is undertaking to qualify as a Competent Person as defined in the 2004 Edition of the "Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves". The information in this report that relates to Exploration Results is based on information compiled by Mr. Jeremy Read who is a Member of the Australasian Institute of Mining and Metallurgy. Mr Read is a full-time employee of the Company. Mr. Read has sufficient experience which is relevant to the style of mineralisation and type of deposit under consideration and to the activity which he is undertaking to qualify as a Competent Person as defined in the 2004 Edition of the "Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves". Mr. Read and Mr Mujdrica consent to the inclusion in the report of the matters based on information provided by them and in the form and context in which it appears. NOTE: For further information contact Jeremy Read Managing Director Tel: +617 3218 0202 Mobile: 0409 484322 Email: jeremy@discoverymetals.com.au Jamie Wright RFC Corporate Finance Ltd (Nomad) Tel: +618 9480 2508 Email: Jamie.Wright@rfc.com.au Richard Hail Fox-Davies Capital Ltd (AIM Broker) Telephone: +44(0) 20 7936 5200 Email: Richard.Hail@fdcap.com ---END OF MESSAGE---