Rockgate Capital Corp.

Rockgate Capital Corp.

May 18, 2010 08:31 ET

Rockgate Announces Positive Metallurgy Results with Recoveries of 90% for Uranium and 77.5% for Silver, Falea U-Ag-Cu Project, Mali, West Africa

VANCOUVER, BRITISH COLUMBIA--(Marketwire - May 18, 2010) - Rockgate Capital Corp. (TSX VENTURE:RGT) (the "Company") is pleased to announce positive results from preliminary metallurgical testwork completed on the North Zone at the Falea Uranium Silver Copper project by SGS South Africa Mineralogical Services. Initial testwork is very favourable with uranium recoveries of approximately 90% in 48 hours and 86% in 6 hours using conventional acid leach at ambient temperature. Silver recoveries of approximately 77.5% using cyanide leach were also achieved.

The preliminary metallurgical testwork and general mineralogical characterization was completed on a 55 kilogram composite sample collected from coarse laboratory rejects from the North Zone at the Falea Uranium Silver Copper deposit. The study sample material consisted of retained crushed diamond drill core from samples submitted to ALS-Chemex in Bamako, Mali. The study used X-Ray Diffraction (XRD) and Bulk Modal Analysis (BMA) techniques to characterize the sample. Deportment studies further characterized uranium, silver and sulphur species ahead of metallurgical testwork. Metallurgical testing included leach tests for uranium-copper, and silver, as well as flotation and comminution testwork. Important points described in the study are summarized below:

  • Uranium leach tests indicate approximately 90% recovery in 48 hours with 86% recovery in 6 hours with acid consumption of 66 kg/t H2SO4, using ambient temperature Johannesburg tap water.
  • Uranium species are all readily leachable and include uraninite and/or pitchblende, and coffinite.
  • Silver leach tests indicate approximately 77.5% recovery after 48 hours with cyanide consumption of 3.11 kg/t NaCN.
  • Flotation tests indicate that copper and silver are "fast floating" with recoveries of up to 95% copper and 94.9% silver after 3 minutes.
  • Silver minerals include native silver and sulphides, likely acanthite (Ag2S) and jalpaite (Ag3CuS2).
  • Uranium minerals are coarser than silver minerals suggesting that leaching uranium first will likely improve subsequent recovery of silver.
  • The composite sample grades 0.357% U3O8, 405 grams per tonne Ag, and 0.16% Cu.
  • Bond Ball Mill Work Index is 17.5 kWh/tonne, reflecting high silica content.
  • Gangue mineralogy comprises quartz (77%), muscovite (16%), chlorite (2%), and feldspar (0.7%).
  • Sulphide minerals predominantly comprise pyrite (0.6%), chalcopyrite (0.4%), with trace amounts of chalcocite/covellite, galena, gerdorffite (NiAsS), cobaltite, arsenopyrite, and pentlandite.

Silver leach recoveries can likely be improved using a finer grind and/or employing a stronger cyanide solution. Further testwork is required to optimize silver leach recoveries. Similarly, further flotation testing will focus on optimization of copper and silver concentrates.

Based on initial testwork, a possible effective process route is as follows:

  1. Fine grinding of the ore (80% passing 75 to 65 micrometers);
  2. Recovery of uranium by standard acid leach;
  3. Neutralization;
  4. Recovery of silver by cyanide leaching (optimal leach parameters still to be determined);
  5. Sulphide flotation to recover most of the remaining copper and possibly the remaining silver.

VP Exploration Lorne Warner commented, "Our first bulk sample from Falea produced excellent results and will serve to guide us in further test work. The leach and flotation tests confirmed very high recoveries of the uranium, silver and copper and identified a possible process route using conventional technology. Further metallurgical testwork will focus on optimization and development of differential copper and silver concentrates. Diamond drilling is continuing to infill and expand the North Zone Area. The recent discovery of mineralization over four kilometres from known zones confirms the high potential of Falea to host significantly more mineralization."

Mr. Lorne Warner, P. Geo, Director and VP Exploration, is the Qualified Person for the Company under NI 43-101.


Karl Kottmeier, President

Neither TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this release.

Contact Information

  • Rockgate Capital Corp.
    Karl Kottmeier
    (604) 678 8941
    Rockgate Capital Corp.
    Kirk Gamley
    VP Corporate Development
    (604) 678 8941
    (604) 689-7442 (FAX)