Red Back Mining Inc.
TSX : RBI

Red Back Mining Inc.

October 27, 2009 08:30 ET

Red Back Announces Heap Leach Results at Tasiast

VANCOUVER, BRITISH COLUMBIA--(Marketwire - Oct. 27, 2009) - Red Back Mining Inc. (the "Company" or "Red Back") (TSX:RBI) is pleased to announce the results of the first phase of Metallurgical test work aimed at developing commercial heap leach operations at its Tasiast Gold Mine in Mauritania. Heap Leaching will add a third processing stream at Tasiast in addition to the 2.5 mtpa (nameplate) CIL plant and Dump Leaching of lower grade oxide ore. The current Measured and Indicated Resource at Tasiast includes a significant amount of lower grade fresh material which is not part of the Reserves, as this lower grade material is not processed either through the CIL plant or the Dump Leach operation. Red Back's intention is to commence heap leaching of this fresh ore in 2011.

The first phase of heap leach test work has quantified significant recovery improvements through the application of High Pressure Grinding Rolls (HPGR) technology. Samples representative of the main ore types (Piment and West Branch) were prepared for column leach testing by conventional crushing to P80 8.5mm and by HPGR to P80 7.4mm. Bottle roll and column leach tests were then completed on all samples by Wardell Armstrong in the UK.

The average increase in recovery with the HPGR samples over conventional crushing was 21% for an average recovery of 59%.

 HPGR
Crushed
Conventional Crushed
Bottle Roll68%36%
Column Leach59%38%

Percolation and agglomeration tests are underway and will be completed shortly. A further test work program has commenced on 30 additional samples from the Piment and West Branch ore bodies to provide variability results for recovery, percolation and agglomeration (if required) and to determine HPGR design parameters. This program is scheduled to be completed in the first quarter of 2010. The table below shows the current Tasiast resource (News Release: September 14, 2009) at a range of cut offs for both oxide and fresh rock:

OXIDECut-OffMeasured and IndicatedInferred
 Au g/t  Au g/t 
0.237.50.831.007.90.60.14
0.426.61.050.904.20.80.11
0.618.11.310.762.51.00.08
0.812.21.600.631.41.30.06
1.08.41.920.520.81.60.04
        
FRESHCut-OffMeasured and IndicatedInferred
 Mt Au g/t Moz  Mt Au g/t Moz
0.2113.81.063.8838.20.91.06
0.490.11.263.6526.51.10.95
0.666.81.533.2818.31.40.82
0.849.71.812.9012.91.70.70
1.037.92.102.569.42.00.60

The current operational oxide dump leach cut off grade is 0.15g/t. Based on anticipated operating costs and a gold price of $700, the Company estimates that the cut off grade for heap leaching will be in the region of 0.4g/t. Cut-off grade for Tasiast CIL feed is currently approximately 0.8g/t.

Commenting on the metallurgical testing to date, Richard P. Clark, President and CEO, said: "The introduction of heap leach operations at Tasiast will substantially increase the Tasiast Reserve and greatly enhance the economics and life of the Project. The large quantity of lower grade sulphide ore and the operating environment at Tasiast seem very well suited for heap leach processing. Upon completion of final testwork and design in Q1 2010, we will immediately proceed to construction and commercial production in 2011. Tasiast just keeps on delivering and exceeding expectations."

About Red Back

Red Back Mining Inc. is an unhedged African focused mid-tier gold producer. It owns and operates the Chirano Gold Mine in Ghana (90% interest) and the Tasiast Gold Mine in Mauritania (100% interest). Major plant expansions at both Chirano and Tasiast are complete. Aggressive exploration programs aimed at increasing the Company's resource and reserve base at both Chirano and Tasiast are ongoing.

The technical contents of this release have been reviewed by Hugh Stuart, BSc., MSc, a Qualified Person pursuant to NI 43-101. Mr. Stuart is the VP - Exploration of the Company and a Member of the Australasian Institute of Mining and Metallurgy. Samples are prepared and analyzed by fire assay using a 50 gram charge at the SGS facility at the Tasiast mine site and at the SGS facility in Kayes, Mali in compliance with industry standards. Field duplicate samples are taken and blanks and standards are added to every batch submitted. Selected samples from this lab are check assayed each month at other SGS laboratories worldwide.

This News Release contains forward looking statements which are subject to a variety of risks and uncertainties which could cause actual events or results to differ materially from those reflected in the forward looking statements. The Company does not intend to update this information and disclaims any legal liability to the contrary.

On behalf of the Board of Directors,

Richard P. Clark, President

Contact Information

  • Red Back Mining Inc.
    Simon Jackson
    VP-Corporate Development
    604-689-7842
    or
    Red Back Mining Inc.
    Sophia Shane
    Investor Relations
    604-689-7842
    www.redbackmining.com