Promising Metallurgical Test ResultsLooking good. :-)
La Mancha Resources Inc. (TSX:LMA - News; hereinafter "La Mancha" or the "Company") is pleased to report that metallurgical test work conducted on samples from its 2008-2009 Volcanogenic Massive Sulfide ("VMS") exploration program at the Hassai pit on its Hassai property in Northeast Sudan suggests that the supergene and primary zone materials respond well to flotation and produce high-grade concentrates. Results from the Hadal Awatib composite are not yet available.
In preparation for the upcoming Preliminary Economic Assessment ("PEA") for the VMS project, La Mancha retained the services of SGS Canada Inc. of Lakefield, Ontario, Canada ("SGS") to conduct Bench Scale and Locked-Cycle Flotation test work, and mandated AMEC Minproc to prepare the PEA based on the metallurgical test work results.
Table 1, as shown below, highlights the initial results for SGS's metallurgical test work. Due to the different Hassai pit material, a Supergene composite (based on the copper-enriched zone) and a Primary composite (based on the bulk of the resource) were developed from samples sent to SGS in May, 2009.
Table 1:
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Final Concentrate Final Concentrate
Hassai pit samples Head Grade Grade Recovery
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Cu, % Au, g/t Cu, % Au, g/t Cu, % Au, %
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Supergene composite 7.31 7.26 30.2 25.1 87.3 73.1
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Primary composite 1.90 1.95 25.1 11.6 84.9 38.3
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The flotation test work shows good metal recoveries, creating a saleable copper concentrate. Additional test work was performed on the flotation tailings to enhance gold recovery. The results were very positive, giving overall gold recovery (including the copper concentrate above) of 92% for the Hassai pit Supergene composite and 75% for the Hassai pit Primary composite. Further analyses are currently underway to see if this process can be economically achieved. More details on the mineralogy, flotation test work and gold extraction from flotation tailings tests performed by SGS are provided in the Technical Note section.
Although it is too early to draw any conclusions from these results and the impact they will have on the outcome of the PEA, Dominique Delorme, President and CEO of La Mancha, stated that he was very pleased: "The 48 million tonnes 43-101 inferred resource estimate announced in and November 2009 had already established that our VMS resource was of an impressive size.(1) Today, we have taken another step in the right direction, with metallurgical test results suggesting that the material responds favorably to traditional copper flotation concentration and gold leaching processes. Copper concentration to over 25% copper at a copper recovery rate of up to 90% is very encouraging."
(1) On November 4th, 2009, the Company announced a first 43-101 inferred resource estimate for the VMS project of 48.48 million tonnes at an average grade of 1.33 g/t Au and 1.23% Cu representing 2.08 million ounces of gold (0.83 million ounces attributable to La Mancha) and 576,000 tonnes of copper (230,400 tonnes attributable to La Mancha).
In preparing the PEA for La Mancha's VMS project, AMEC Minproc used the metallurgical test work results to develop assumptions on the recovery rates to be expected for gold and copper in the various parts of both deposits. The test results were adapted to the resource grades and applied to the concentrator mass balance model being used for the PEA. Based on the currently understood material variability, three types are expected for the concentrator feed: Hassai South Supergene, Hassai South Primary and Hadal Awatib. Tests have not been conducted on Hadal Awatib, but the mineralogy is expected to be similar. Test results have been extrapolated to the three material types, and then modeled to give concentrate grades and metal recoveries as shown below in Table 2. Metal recovery assumptions in Table 2 vary compared to the Locked-Cycle test-work results in Table 1. Material grade differences and batch flotation test results were considered by AMEC Minproc when making the assumptions.
Estimated results for flotation concentration are shown for three material types defined in the Inferred resource announced on November 4, 2009:
Table 2: AMEC Minproc Flotation Concentration Estimation Results
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Material average Concentrate Final Concentrate
grade grades Recovery
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Cu, % Au, g/t Cu, % Au, g/t Cu, % Au, %
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Hassai Supergene 2.75% 2.29 32% 22.0 81% 67%
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Hassai Primary 1.37% 1.49 25% 11.0 90% 36%
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Hadal Awatib 0.99% 1.18 25% 10.0 85% 29%
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Bill Plyley, COO of La Mancha Resources, commented: "The assumptions in Table 2 that will form the basis for the copper concentrator design in the upcoming PEA compare favorably with similar VMS projects. Test work by SGS on leaching the tailings from the concentrator to recover additional gold was also encouraging and, while it was not included in these assumptions, it could further improve the gold recovery."
An initial review of the VMS resource suggested treatment by conventional flotation concentration followed by cyanide leaching (CIL) of the tailing products to increase gold recovery. Production of a copper concentrate (also containing gold) to be sold to a secondary processor was envisioned. In addition, concentrator tailings were expected to be leached to produce gold bullion from a conventional CIL plant. Test work results to date confirm these hypotheses.
NEXT STEPS
Over the next two months, the Company will continue to assist AMEC Minproc in the preparation of a PEA for the Hassai VMS project. Results of this PEA are now expected at the beginning of the third quarter. The main objective of this PEA is to provide a first look at the economic viability of a VMS project at the Hassai property on the basis of a series of assumptions that include operating and development costs, and to provide a recommendation for the future of the project.
TECHNICAL NOTE
Mineralogy
A sub-sample of the Hassai Supergene composite and Primary composite, at a grind size of 80% passing 100 micrometers, was submitted for high-definition mineralogical characterization. The predominant sulfide minerals in the Hassai Supergene composite were pyrite (55%) and chalcopyrite (23%), accounting for 78% of the mineral mass. As for Hassai Primary composite, pyrite and chalcopyrite were the predominant sulfide minerals accounting for 80% and 6% of the mineral mass respectively. The most abundant non-sulfide gangue mineral type was silicates, which accounted for 7% of the mineral mass.
Flotation Test Work
A total of thirteen rougher kinetics and batch cleaner flotation tests were performed on the Hassai Supergene zone composite and Primary zone composite. In addition, a locked-cycle test was performed on each of the two composites. The test work explored the effect of primary grinding, pulp pH, collector dosage and re-circulating loads. The locked-cycle tests are designed to emulate the metallurgical response in the concentrator plant. The test results are used as a basis for preliminary plant design. As reported in table 1, the final copper recovery for Hassai Primary composite in the locked cycle test was 84.9% following an average open circuit rougher copper recovery of 87%. However, in identical roughing stages in batch tests (with the same sample) the rougher copper recoveries ranged from 93% to 95%. On this basis it has been assumed that the locked cycle recoveries are underestimated due to poor roughing stage performance.
A final concentrate from locked-cycle tests (Cycle F) for each of the Hassai Supergene composite and Primary composite was submitted for detailed concentrate analysis. For the Hassai Supergene composite, the final concentrate copper grade was 30.2% with 25.1 g/t gold. As for the Hassai Primary composite, copper was graded 25.1% with 11.6 g/t gold. No deleterious elements were present in either final concentrate, indicating that the concentrate should be readily saleable.
Gold Extraction from Concentrator Tailings
Gold extraction from a series of flotation test products was evaluated at a scoping level. Pyrite scavenger concentrate and 1st cleaner scavenger tailing representing both the Supergene and Primary zone materials were tested. These products were generated in locked-cycle tests. The initial pair of tests, one on each composite, was conducted on pyrite scavenger concentrate generated in smaller-scale batch tests. The primary purpose of these tests was to approximately determine the potential for gold recovery. Parameters evaluated in these tests included leach retention time, feed particle size and cyanide concentration.
Gold leach processing of the concentrator tailings is still being modeled by AMEC Minproc, and the results are not yet available.
QUALIFIED PERSONS
Metallurgical test work was conducted by SGS Canada Inc. in Lakefield, Ontario, Canada, and was under the direct supervision of James MacDonald, Senior Metallurgist. James has 25 years experience in the mineral processing field and is currently a senior metallurgist/project manager within the SGS Canada, Metallurgical Operations, Gold Group.
The PEA is being prepared by AMEC Minproc in Perth, , under the supervision of Dean David, Process Consultant. Dean has 27 years experience in mineral processing research, operations, management and consulting. His expertise covers most aspects of mineral processing technology. He has a Bachelor of Applied Science (Metallurgy) from the South Australian Institute of Technology SA, Australia. Dean was Manager Process at AMEC Minproc for two years and since mid 2005 has been Process Consultant. He participated in the majority of mineral processing studies and projects conducted by Minproc in the past six years, typically in a reviewing and consulting role.
Bill Plyley, COO of La Mancha acts as project coordinator of the project. Mr. Plyley is a seasoned mining veteran, with more than 35 years management and hands-on experience in international mining industries. Mr. Plyley holds a BSc. in Metallurgical Engineering from the Mackay School of Mines, University of Nevada, Reno.
Dean David and Bill Plyley are Qualified Persons as defined by National Instrument 43-101. They have read National Instrument 43-101 of the Canadian Securities Administrators ("NI 43-101") and have ensured that this press release is in compliance with it.
The 43-101 resource figures quoted in the text of this press release were disclosed in press releases issued on 10, 2009, and November 4, 2009, and are detailed in two technical reports dated October 26 and December 21, 2009.