Update - Macalder metallurgical testwork

RNS Number : 1634I

Red Rock Resources plc

09 June 2011

 



RED ROCK RESOURCES PLC

Update - Macalder metallurgical testwork

Dated: 9 June 2011

Red Rock Resources plc ("Red Rock" or the "Company"), the gold mining and exploration company with projects in Kenya, and Colombia, and interests in steel feed, uranium, and rare earths reports on results of the Phase 2 metallurgical testwork at the Macalder tailings project in Kenya.

Macalder tailings

The Macalder tailings deposit is at the previously operated Macalder VMS base metal mine situated in South Nyanza District in the South West of Kenya, close to the shores of Lake Victoria.

The Macalder Mine processed a VMS base metal deposit for the recovery of the copper mineralisation which was concentrated by flotation and roasted to a calcine for dissolution of the copper values which were subsequently precipitated onto scrap iron. Calcine tailing was then cyanide leached for the recovery of the gold and silver values. The cement copper was transported to the Kilembe Mines Smelter situated in Jinja, Uganda.

The gossan material from the upper levels of the VMS deposit was mined and processed for the recovery of the gold and silver values by a combination of amalgamation and cyanide leaching.

The tailing from the flotation, the calcines from the roast-leach circuit, and the gossan tailing are available on site for further processing.

On 19 August 2010 the Company announced an Indicated Mineral Resource in the tailings of 1.424m tons at a grade of 1.64 grams per ton of Gold.

Metallurgical Testwork

Phase 1 testwork was carried out to delineate the flowsheet. The testwork based upon variability samples from throughout the tailing resource indicated that a conventional cyanide leach plant would be required. Preconcentration of the tailing was shown to be non-viable.

Phase 1 testwork was carried out on thirteen "composite" samples of the various types of tailing, identified visually, which were despatched to Amdel Laboratories in Western Australia. Amdel's scope of work was to determine the basic characteristics of the samples in conjunction with a preliminary metallurgical assessment with respect to the recovery of the value metal contents. The results indicated that a direct cyanide leach of the as received samples to 48 hrs was adequate for the recovery of the gold values. However additional testwork was recommended as Phase 2 on master composites of the tailing dam materials in order to establish a more accurate assessment of the process flowsheet design parameters.

Phase 2 testwork was carried out into metallurgical recovery of Gold and Silver based upon the preferred flowsheet. Composites representing the differing materials within the resource were tested to establish the basic leach parameters. The results indicated an average recovery of nominally 65% of the gold, and 10-20% recovery of the silver. The flowsheet will however reduce the amount of grinding required, and a reduction in the leach residence time from that anticipated from the Phase 1 testwork.

The Phase 2 testwork was carried out on composites made from the differing types of material within the tailing dam as supplied during Phase 1 testwork with one additional sample which represented material from the tailing dam wall.

A detailed size distribution with assaying of the individual size fractions shows that the gold and the silver content is evenly distributed throughout the full size range of all samples indicating that the feed tonnage and grade to the process plant cannot be upgraded by physical sorting.

Leach testwork on the individual composites indicated that there was only marginal variations in recovery when comparing the leach recovery of "as received" samples with leach results on samples ground to nominal 40 microns.

A Master composite made from combining the individual composites also showed that the improvement in recovery from the "as received" samples through nominally 100, 80, 60, and 40 microns was marginal.

An assessment of the leach recovery at 8, 24, 48, and 72 hours indicated that an 8 hour leach would reduce the value metals recovery significantly. The recoveries at 24, 48, and 72 hours were much closer.

Phase 3 testwork is planned to define the design parameters of the preferred flowsheet and to improve on the resource definition with respect to feed variation.

Preliminary economics on the project are positive. The flowsheet will be a conventional cyanide agitation leach and Merrill Crowe recovery plant.

Besides the metallurgical study, separate baseline and environmental studies are under way. Initial work supports the conclusion that the reprocessing of the tailings materials can be carried out in a manner that will have benefits in terms of cleaning up legacy environmental impacts from the historic mining operation.

The metallurgical information is this release has been reviewed and approved for release by Leonard Holland, BSc(Hons), a consultant to the Company. Mr Holland is a Chartered Engineer, a Fellow of the Institution of Materials Mining and Metallurgy and a Fellow of the Minerals Engineering Society.

Enquiries:

Andrew Bell	020 7402 4580 or 07766 474849	Red Rock Resources plc	Chairman
Sandra Spencer	020 7402 4580 or 07757 660 798	Red Rock Resources plc	Public and Investor Relations
Peter Trevelyan-Clark/ Ben Jeynes	020 7444 0800	Religare Capital Markets	Nominated Adviser
Nick Emerson	01483 413500	Simple Investments Ltd	Broker

Updates on the Company's activities are regularly posted on its website, www.rrrplc.com.

 

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