Global Minerals Updates On-Going Metallurgical Studies
VANCOUVER, BRITISH COLUMBIA -- (Marketwire) -- 08/02/12 -- Global Minerals Ltd. (TSX VENTURE: CTG)(FRANKFURT: DFP) is pleased to announce this update of on-going metallurgical testing to assess the most commercially beneficial method to produce silver/copper concentrates from its high-grade Strieborna deposit for sale to custom smelters.
Test work will be used to design the process facilities to be included in a Preliminary Economic Assessment. Three basic process alternatives are being considered. Each starts with simple flotation concentration to recover the primary silver/copper bearing minerals. Downstream processing of these concentrates may include the leaching of the concentrates to recover contained antimony (Sb) and produce it as a marketable co-product. A third process alternative includes roasting or selective flotation of the concentrates to safely eliminate mercury (Hg) prior to shipment to the smelter.
Blue Coast Metallurgy Ltd, the Company's principal metallurgical consultant, has recommended a series of follow-up investigations planned to yield sufficient criteria for initial engineering design. These tests are now under way. Further information regarding the metallurgical program can be found on the Company's website: http://globalminerals.com/projects/metallurgy/.
Flotation Concentration Test Results
The test results using common flotation concentration were previously reported (News Release Nov 16, 2011: http://globalminerals.com/2011/11/global-makes-significant-progress-and-adds-to-its-board-of-directors/). The best overall grade/recovery curve indicated a silver/copper concentrate assaying approximately 5800g/t Ag and 25% Cu at a 94% silver recovery and a 96% copper recovery. Concentration was by a two-stage concentration (rougher/cleaner) process. On-going testing is now underway to improve the concentrate grades and recovery and provide to data for engineering design parameters.
Antimony Recovery
Recovering antimony from the concentrate prior to shipment to a custom smelter has two potential benefits. The antimony recovered from the concentrate to a solution can be used to form various marketable antimony products for sale as by-products. Secondly, the residual concentrate containing silver and copper can be sent to a smelter with no or little penalty for antimony content. The potential for antimony removal from the concentrates by leaching in caustic solutions was evaluated.
The leaching tests, at varying temperatures and reagent concentrations, yielded recovery of antimony to solutions from 73 to 97%. The leaching tests also measured mercury and arsenic recovery from the concentrates to the solutions. Mercury extraction varied from 67% to 92% while arsenic recovery varied from 6% to 19%.
On-going testing will evaluate leaching at higher temperatures. Conceptual-level design parameters for a hydrometallurgical facility to leach concentrates will be defined if test results warrant it.
Mercury Removal
The level of mercury in Strieborna concentrates, without removal prior to shipment, renders the concentrate unacceptable at custom copper smelters. Hence, ways to reduce the mercury (and antimony) contents prior to shipping the material to a copper smelter are required. The preliminary results indicate that roasting of concentrates prior to shipment leads to a commercially viable concentrate with virtually all mercury eliminated.
A number of experimental tests were conducted to examine mercury (and antimony) removal from Strieborna copper concentrate by first roasting the concentrate to volatilize mercury followed by an oxidizing roast to volatilize antimony oxides and some sulphur.
Mercury elimination in four of the five tests was 99.9%. One test at lower temperatures resulted in a 69.9% elimination of mercury from the concentrate. Antimony elimination was more problematic ranging from less than 1% to 34%. Nevertheless marketing studies indicate that smelters would accept these concentrates (with an appropriate penalty).
The tests were designed and supervised by pyrometallurgical specialists associated with Blue Coast Metallurgy Ltd.
Further testing to provide design parameters for an economic assessment is now on-going under the supervision of Global and Blue Coast. Roasting options (together with environmentally safe recovery of the mercury for sale or other disposal) are being considered and will be evaluated as part of a Preliminary Economic Assessment the Company is preparing. The Company is also investigating the use of selective flotation to evaluate the possibility of removing mercury bearing minerals which could, if successful, eliminate the need for concentrate roasting.
About Strieborna
Strieborna is a high-grade silver-copper-antimony vein type deposit in an historic mining district near the town of Roznava in eastern Slovakia. The current resource, NI 43-101 dated April 22nd 2008, occurs within a mineralized structure 1.2 km long, 600 m deep and an average thickness of 3.4 m. The resource has been defined by diamond drilling and a series of four horizontal underground drifts totaling 3,000 meters. The mineralization is open in various directions along the vein structure. Other similar structures have been identified within the mining and exploration leases and will be the focus of future exploration drilling programs.
In addition to the upside of the exploration potential and the high-grade nature of the polymetallic mineralization, the project has excellent infrastructure, including sufficient electrical power, railway access, paved highways and a work force experienced with underground operations. Underground access has been achieved through existing mine workings.
Global Minerals Ltd. is a Canadian exploration and development company focused on developing its high-grade silver/copper deposit in Slovakia.
QUALIFIED PERSON: William Pincus, M.Sc., C.P.G. and CEO for Global is the Qualified Person (QP) under NI 43-101 responsible for the Strieborna program. He has verified the results and other data disclosed in this news release.
FORWARD-LOOKING STATEMENTS AND FORWARD-LOOKING INFORMATION: This news release contains certain "forward-looking statements" within the meaning of applicable Canadian securities laws. Forward-looking statements and forward-looking information are frequently characterized by words such as "plan", "expect", "project", "intend", "believe", "anticipate", "estimate" and other similar words, or statements that certain events or conditions "may" or "will" occur.
FORWARD-LOOKING STATEMENTS are based on the opinions and estimates of management at the date the statements are made, and are subject to a variety of risks and uncertainties and other factors that could cause actual events or results to differ materially from those projected in the forward-looking statements. These factors include the inherent risks involved in the exploration and development of mineral properties, the uncertainties involved in interpreting drilling results and other geological data, fluctuating metal prices, the possibility of project cost overruns or unanticipated costs and expenses, uncertainties relating to the availability and costs of financing needed in the future and other factors. The Company undertakes no obligation to update forward-looking statements if circumstances or management's estimates or opinions should change. The reader is cautioned not to place undue reliance on forward-looking statements.
Readers are advised that National Instrument 43-101 of the Canadian Securities Administrators requires that each category of mineral reserves and mineral resources be reported separately. Readers should refer to the annual information form of Global for the year ended June 30, 2010 and other continuous disclosure documents filed by Global since September 30, 2010 available at www.sedar.com, for this detailed information, which is subject to the qualifications and notes set forth therein.
For further information about Global, visit www.globalminerals.com.
Neither the TSX Venture Exchange nor the Investment Industry Regulatory Organization of Canada accepts responsibility for the adequacy or accuracy of this release.
Contacts:
Global Minerals Ltd.
William Pincus
President and CEO
wpincus@globalminerals.com
Global Minerals Ltd.
Ms. Lubica Parilakova
Manager Investor Relations
604.669.2355
lparilak@globalminerals.com
www.globalminerals.com