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Message: Results of Bio-Leach Testing on Bulk Flotation Concentrate
| May 7, 2009 | |
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Inter-Citic Reports Results of Bio-Leach Testing on Bulk Flotation Concentrate from the Dachang Gold Project
Gold CIL recovery of 89% on bio-leached flotation concentrate. Predicted overall gold recovery of 85% to dore. Results provide the Company with an economically viable process flowsheet. |
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TORONTO, ONTARIO--(Marketwire - May 7, 2009) - Inter-Citic Minerals Inc. (TSX:ICI) ("Inter-Citic" or "the Company") President and CEO James Moore, is pleased to report results received from the bio-leaching/CIL test work conducted on a bulk flotation concentrate sample from the Dachang gold project. The results reflected in this press release should be read in conjunction with the bulk flotation concentrate results first reported by the Company in a Press Release dated March 2, 2009. The results showed that high gold leach recoveries of 89% can be achieved by bio-leaching and conventional CIL. Fast leach kinetics were observed with 88.6% of the gold leached into solution after 4 hours. The leach kinetics curves also showed no signs of "preg robbing" occurring. "Preg-robbing" is where the presence of "preg-robbing carbon", defined as carbonaceous material that preferentially absorbs gold from solution thereby reducing gold leach recoveries. Overall gold recoveries to dore are predicted to be 85%, assuming 96% for the flotation stage, 89% for the BIOX/CIL stage, and 99% for solution/goldroom losses. CEO of Inter-Citic Minerals Inc., Mr Jim Moore, commented: "We are obviously very pleased with these test results that confirm that the Dachang flotation concentrate is amenable to processing by bio-leaching and conventional CIL. An overall combined gold recovery to dore of 85% is an excellent result for Dachang and now provides the Company with an economically viable metallurgical process flowsheet. Our test work continues to evaluate alternate refractory process routes to determine the most economically viable process for Dachang." DETAILS OF THE TESTWORK PROGRAM The testwork program was carried out in three stages: I. Stage 1: Bulk flotation test conducted on a global bulk composite, composited from drill core representing the various lithology zones from the Dachang deposit. II. Stage 2: Bio-leach amenability test (BAT) carried out on the bulk sulphide concentrate adopting the Bacox process and bacterial strain. III. Stage 3: CIL testing of bio-leached product. Stage 1: Bulk Flotation Test A bulk flotation test was conducted on the Dachang global composite sample, using standard conditions, to produce bulk concentrate for BAT work. Results of the bulk flotation test are shown in Table 1. Table 1: Bulk Flotation Test
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Grind Test Conc. Concentrate Assay Metal Distribution
P80 No. Yield -----------------------------------------------------
(mic- Au Ag ST As Au Ag ST As
rons) (%w/w) (g/t) (g/t) (%) (%) (%) (%) (%) (%)
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75 WH 1626 9.17 41.8 2.5 13.0 6.63 96.13 45.78 97.05 96.08
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Stage 2: Bio-Leach Amenability Test The BAT test is a standard laboratory test devised to determine the amenability of a high arsenic concentrate to bio-leach technology. The Burnie laboratory BAT procedure follows the Goldfields BIOX(R) technology. The BAT flowsheet consists of a regrind stage (P80 of 20 microns) followed by bacterial adaptation and inoculums build-up. The flotation concentrate is then subjected to bio-oxidation leach for 24 days. After completion of the BAT the bio-leached product was sent for cyanidation leaching. Stage 3: Conventional CIL Test The conventional CIL test was conducted for a reduced leach residence time of 12 hours, and with high coconut shell carbon concentrations, in order to minimize the 'preg-robbing' effect. The leach kinetics was rapid with 88.6% of the gold leached into solution after 4 hours. The final overall gold leach recovery was circa 89% after 12hours of leaching. There was no evidence of 'preg robbing' exhibited during the conventional CIL test. Cyanide and lime consumptions were 10.08 kg/tcon and 24.62 kg/tcon respectively. These are considered to be typical of cyanidation leaching, post bio-leach stage. The BIOX(R) Process The process itself uses a combination of three bacteria that occur naturally, thiobacillus ferrooxidans, thiobacillus thiooxidans and leptospirillum ferroxidans, to break down the sulphide mineral matrix in the ore being treated, thus freeing the occluded gold for subsequent cyanidation. The bacteria attach themselves to the metal sulphide surfaces in the ore, resulting in the accelerated oxidation of the sulphides. The BIOX(R) process involves the continuous feeding of the flotation concentrate slurry to a series of stirred reactors. An overall process flow diagram for a typical BIOX plant is shown accompanying this press release on the Company's website: www.inter-citic.com. Further testing of the Albion Process (Float/UFG/POX/CIL), as an alternative process route to float/UFG/BIOX/CIL, is presently ongoing at HRL Testing facilities in Brisbane. The bio-leach amenability (BAT) test work was conducted at the Burnie Laboratory in Tasmania and subsequent CIL testing of the bio-leached product was carried out by AMMTEC laboratories in Perth. AMMTEC Pty Ltd. is one of the largest metallurgical and mineral testing consultancies in the world. The metallurgical testwork program was prepared and supervised by Metallurg Pty Ltd. under the supervision of Mr Gary Patrick, an external consultant to the Company. Mr Patrick has sufficient experience, which is relevant to the style of mineralization 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 Patrick consents to the inclusion in this report of the matters based on his information in the form and context in which it appears. Mr. Michael W. Leahey, P.Geo., the Company's internal Qualified Person under the requirements of National Instrument 43-101, has reviewed a copy of this press release. On Behalf of the Board: James J. Moore, President & CEO ABOUT INTER-CITIC: Toronto-based Inter-Citic Minerals Inc. is an exploration and development company with properties in the People's Republic of China, including its Dachang Gold Project in Qinghai Province. Inter-Citic is listed on the TSX under the symbol ICI. Inter-Citic's website is www.inter-citic.com. |
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