Antares Minerals Inc.

Antares Minerals Inc.

April 08, 2010 13:40 ET

Antares Reports Haquira East Sulphide Mineral Flotation Recovery Tests Show Positive Results

WATERDOWN, ONTARIO--(Marketwire - April 8, 2010) -

  • Rougher concentrate recoveries up to 95% Cu
  • Project capable of delivering high-quality, clean concentrate
  • Estimated recovery of 89.3% copper, 72% gold and 57% molybdenite in final concentrate

Antares Minerals Inc. ("Antares") (TSX VENTURE:ANM) is pleased to announce that it has received results of a bench-scale scoping metallurgical study on two composite samples of primary copper sulphide-bearing drill core from the Haquira East mineralized zone at the Haquira copper project. The study was completed by Resource Development Inc. (RDi), based in Golden, Colorado. The metallurgical test work included sample preparation and characterization, mineralogical examination, Bond's ball-mill work index determination, grind studies and rougher flotation recovery tests. The highlights of the study are the following:

  • Rougher concentrate recovery of 95% and 92% of copper from Composite No.1 and No.2, respectively.
  • The first two minutes of rougher flotation recovered over 85% of copper at a concentrate grade of 29% to 30% Cu. 
  • The rougher concentrate analysis showed very low levels of any deleterious elements such as arsenic, lead, phosphorus etc.
  • The rougher flotation scoping tests indicated that a simple reagent suite consisting of potassium amyl xanthate (PAX), diesel fuel and methyl isobutyl carbonyl (MIBC) will float the majority of the copper sulphides, gold, and molybdenite in the ore.
  • Bond's ball-mill work index was determined to be 12.76, which is within the range of values reported for porphyry copper ores.
  • RDi projects that the sulphide-bearing material can be treated with a standard process flow sheet, similar to conventional Cu/Mo ores being processed in the U.S. The estimated overall recoveries for the two composites tested are: 89.3% of copper, 72% of gold and 57% of molybdenite,. Additional test work is required to confirm these recovery values.

RDi emphasized that, while these are excellent results at this stage of the project examination, additional test work is needed to confirm the mineral recoveries, optimum reagent mix, and the full process flow-sheet recommendation.

John Black, President and CEO of Antares Minerals Inc. commented as follows:

"We are pleased with these highly encouraging test results regarding the metallurgical characteristics of the Haquira East primary sulphide material. These results demonstrate that a high-quality, clean concentrate can be produced from Haquira East. While these metallurgical data are based on only two composite samples, the intervals are representative in nature and point to highly favourable processing recoveries using a conventional flow sheet and standard reagents. These results continue to support Antares Minerals' primary mission of adding value to its mineral discoveries."

"Additional test work will be organized to confirm these data and to progress our understanding of the sulphide material at Haquira East. We look forward to completing these studies in 2010."

Discussion of Results

SAMPLE ORIGINATION, PREPARATION AND ASSAY RESULTS: Two composite samples were collected from Haquira East sulphide-bearing drill core and sent to RDi for assay analysis and metallurgical testing. An attempt was made to identify different grades of copper, molybdenum and gold for process testing. The samples consisted of the following drill core intervals:

Composite No.1

Drill Hole # From (m )   To (m )   Interval   Weight (kg )   Lithology
AHAD 098A 342.05     343.80     1.75   6.0     Haquira porphyry
AHAD 098A 381.80     383.45     1.65   5.0     Haquira porphyry
AHAD 102 491.10     493.05     1.95   6.4     Haquira porphyry
AHAD 102 496.50     498.0     1.50   4.4     Haquira porphyry

Composite No.2

Drill Hole # From (m )   To (m )   Interval   Weight (kg )   Lithology  
AHAD 103 269.05     271.05     2.0   7.5     Haquira porphyry  
AHAD 105 168.05     169.95     1.9   6.4     Haquira porphyry  
AHAD 106 217.70     219.70     2.0   6.5     Haquira porphyry  
AHAD 106 241.45     243.45     2.0   7.0     Haquira porphyry  

Each composite was thoroughly blended and crushed to nominal 6 mesh size. The composite sample was then split into 20 individual one-kilogram charges using a twenty-way rotary splitter. A one kg sample of each composite was pulverized to minus 150 mesh and a representative sample split out for copper, molybdenum, gold and silver analyses as well as other elements. The pulverized samples were sent to Florin Analytical Services, LLC, in Reno, Nevada for assaying.

Analytical results for copper, molybdenum, gold, silver, and total sulphur are:

Composite No.1

Copper (Total) Molybdenum   Gold   Silver   Sulphur (Total )
1.592% 40 ppm   0.27 g/t   18.02 g/t   1.06 %

Composite No.2

Copper (Total) Molybdenum   Gold   Silver   Sulphur (Total )
0.754% 275 ppm   0.21 g/t   8.58 g/t   0.62 %

MINERALOGICAL EVALUATION: The two composite samples were investigated microscopically in polished sections to identify mineral constituents that account for contained copper, molybdenum and other metals of interest. Mineralogical work was performed by OTX-Mineralogy of Bountiful, Utah.

Sulphide minerals in Composite No. 1 are comprised of about 50% chalcopyrite, 40% bornite, 4% chalcocite, 4% secondary copper sulphides (digenite-covellite), 1% molybdenite and 1% pyrite. Chalcopyrite and bornite grains are about 75% liberated at a minus 28 mesh grind. Chalcopyrite and bornite grains range from 350 microns down to 5 microns, or smaller. Small plates of molybdenite were observed locked in quartz grains. Molybdenite books exhibit inter-plate gangue that may require fine grinding for liberation.

Sulphide minerals in Composite No. 2 are comprised of approximately 50% bornite, 45% chalcopyrite, 4% molybdenite, and 1% pyrite. The sample contains a significantly larger amount of magnetite-hematite. Molybdenite is closely associated with chalcopyrite and also locked with silicate gangue. Chalcopyrite grains, as small as several microns, were observed locked in silicate gangue.

BOND'S BALL-MILL WORK INDEX: Ten kilograms of ½ core, HQ/NQ size, was crushed to P100 of minus 6 mesh and the sample was used to determine the Bond's ball mill work index at minus 100-mesh grind. The Bond's ball mill work index was determined to be 12.76. This value is similar to those reported for other porphyry copper ores.

FLOTATION TESTS: Eight scoping flotation tests, four on each composite, were performed to recover copper, molybdenum, gold and silver values into a rougher concentrate. Varying concentrations of potassium amyl xanthate (PAX), diesel fuel and methyl isobutyl carbonyl (MIBC) were used in the tests. Two supplementary collectors, known for recovering gold, were tested as additional collectors in the rougher flotation (AP 3477 and AP 404). The other variable investigated was primary grind size (P80 of 100 and 150 mesh). Timed concentrates were collected for a total of 9 minutes of flotation time.

A summary of the test data indicates the following:

  • The rougher concentrate recovered approximately 95% of the copper for Composite No. 1 at a primary grind of P80 of 150 mesh and with a simple reagent suite of potassium amyl xanthate (PAX), diesel fuel and methyl isobutyl carbonyl (MIBC). The molybdenite recovery ranged from 46% to 68%, and gold recovery was approximately 80%. The final rougher concentrate contained 14% to 18.6% Cu.
  • The rougher concentrate recovered 90% to 92.6% of copper, 79.7% to 95% of molybdenite and 43% to 54% of gold for Composite No. 2. The final rougher concentrate contained 7.2% to 12% Cu.
  • Concentrations of potentially deleterious elements (As, Pb, P, etc) are very low resulting in a clean and highly marketable concentrate.
  • Review of the kinetic data indicated that 88% of the copper floated in two minutes of flotation time at a concentrate grade of 29.64% Cu for Composite No. 1 (Test No. 1). For Composite No. 2, two minutes of flotation recovered 78.2% of copper at a concentrate grade of 21.64% Cu (Test No. 5).
  • Precious metal recoveries were reasonable for both composites and molybdenite recovery is dependent on the feed grade. Higher molybdenum feed grades result in higher molybdenite recovery.

PROJECTED PROCESS FLOW SHEET AND METALLURGY: Based on this scoping study, RDi projects a conceptual process flow sheet for the sulphide ores. The flow sheet would consist of crushing and grinding the ore to P80 of 100 to 150 mesh, and floating copper, molybdenum and precious metals in a bulk-rougher concentrate. The bulk-rougher concentrate would be subjected to first bulk-cleaner flotation. The tailings from the first bulk-cleaner flotation would be reground and subjected to scavenger flotation and scavenger-cleaner flotation. The scavenger-cleaner flotation would be combined with first-cleaner flotation concentrate and subjected to second-cleaner flotation. The second-cleaner flotation concentrate would be subjected to Cu/Mo separation and molybdenite would be upgraded in the cleaner circuit. The need for regrind or the number of cleaner flotation stages for the molybdenite upgrading circuit is unknown at this stage of scoping study.

Based on past experience with Cu/Mo plants, an attempt has been made to project the recoveries of Cu, Mo and Au in the proposed process flow sheet. The following assumptions have been made for overall recoveries:

  • Projected rougher recoveries are 93% for copper, 60% for molybdenite, and 75% for gold. Bulk-cleaner flotation circuit will recover 97% of copper and 95% of molybdenite and gold present in the rougher concentrate. 
  • Following the copper/molybdenite separation circuit, 96% of copper and gold and 3% of molybdenite will report to copper concentrate and 2% of copper and gold and 95% of molybdenite will report to molybdenite concentrate. The scavenger flotation tailing will contain 2% of copper, 2% of molybdenite and 2% of gold. Based on the above assumptions, process recoveries are estimated as follows:

Copper concentrate will contain 89.3% of copper and 72% of gold. 
Molybdenite concentrate will contain 57% of molybdenite.

The above estimates are projections based on similar bulk flotation projects. Additional test work is needed to confirm these projections.

About the Haquira Copper Project, Peru

The Haquira project is located in southern Peru and offers excellent potential for an initial low-strip, low-cost SX-EW copper operation with a subsequent transition to a higher grade primary porphyry copper-molybdenum mill/concentrator operation. Antares has recently announced an updated resource estimate for the Haquira project (see press release of February 26th, 2010). The estimate encompasses all the known mineralization at the Haquira East and Haquira West deposits as well as the immediately surrounding areas (Potato Patch zone), but does not reflect the mineralization recently discovered at the nearby Cristo de los Andes prospect. It includes both the near-surface secondary (leachable) copper mineralization as well as the underlying primary (mill/concentrate) mineralization. This resource estimate utilizes all drilling completed to date at the Haquira project (through drill hole AHAD-174). Highlights from this interim resource estimate at a cut-off of 0.3% total Cu for primary mineralization and 0.2% total Cu for leachable secondary mineralization are as follows:

Table 1. Mineral Resource Summary Haquira Project - All Zones - February 2010  
Resource Tonnes     Cu Eq* %    Cu  %   Mo %    Au   Ag   lbs Cu     lbs Cu Eq*  
Classification (millions )                     g/t   g/t   (billions )   (billions )
Primary Copper Mineral Resources (Mill/Concentrate) - 0.3% Cu cut-off  
Measured 68.9     0.78     0.64     0.015     0.045   1.84   0.97     1.18  
Indicated 285.7     0.75     0.63     0.014     0.044   1.78   3.93     4.74  
Inferred 333.7     0.62     0.54     0.009     0.032   1.59   3.94     4.59  
Secondary Copper Mineral Resources (leachable – SX/EW) - 0.2% Cu cut-off  
Measured 59.4     0.52     0.52                   0.68     0.68  
Indicated 155.6     0.44     0.44                   1.52     1.52  
Inferred 72.2     0.41     0.41                   0.65     0.65  

Antares announced in May, 2008, the results of a preliminary economic assessment ("PEA") for the near-surface, SX-EW amenable portion of the Haquira project. This PEA was based upon the an earlier resource estimate announced in October, 2007 which defined leachable resources at Haquira within two deposits (Haquira East and Haquira West) with a combined indicated resource of 133.7 million tonnes at 0.53% total Cu with an additional inferred resource of 43.6 million tonnes at 0.44% total Cu (0.3% total Cu cut-off, leachable secondary copper sulphide and oxide mineralization only). This resource is projected to support a 50,000 t/d SX/EW heap leach operation that will produce an average of 109 million lbs of copper cathode for 11 years of mine life. The capital cost to construct the operation is estimated at US$301 million with a projected IRR of 26.9% and an NPV of US$224 million utilizing a copper price of US$2.00/lb and a discount rate of 8%.

The project is located contiguous to, and immediately south of, Xstrata Copper's Las Bambas Cu-Au project and consists of two blocks of property acquired or optioned under separate agreements as well as additional concessions acquired by Antares for a total of 20,635 hectares of area. Antares has fulfilled the terms of an option agreement and acquired a 100% interest in the original Haquira project by completing optional payments totalling US$15 million over a five-year period (see Antares press release dated March 17, 2005).

Antares also has an option agreement with Minera del Suroeste S.A.C. (MISOSA), a wholly owned subsidiary of Hochschild Mining PLC, whereby Antares can acquire up to a 60% interest in the Cristo de los Andes project, located contiguous to, and immediately south of the Haquira project (see Antares press release dated April 28, 2008).

Additional information about the Haquira project is available on our website at

About Antares

Antares is a successful mineral exploration company with highly experienced technical and management teams. The Company is focused on precious- and base-metal exploration properties in Latin America that can be quickly and cost-effectively advanced to the discovery and production stage. In addition to the Haquira Project in Peru, Antares is also currently exploring the Rio Grande (Cu-Au porphyry) project in Salta Province of NW Argentina in a 50/50 option/joint-venture basis with Pachamama Resources Ltd., a spin-off from Mansfield Minerals Inc.

The TSX Venture Exchange does not accept responsibility for the adequacy or accuracy of this release.

(*) CuEQ = Copper Equivalent is calculated for intervals dominated by primary mineralization using US$1.50/lb Cu, US$500/oz Au, US$10/oz Ag and US$10.00/lb Mo and is not adjusted for metallurgical recoveries as these remain uncertain. Metallurgical recoveries and net smelter returns are assumed to be 100%. The formula used is as follows: CuEQ = Cu% + (Au g/t x 0.4862) + (Mo% x 10.00/1.50) + (Ag g/t x 0.0077). Copper Equivalent contributions are only applied to primary sulphide mineralization.

All of Antares' exploration programs and pertinent disclosure of a technical or scientific nature are prepared by, or prepared under the direct supervision of John Black, Antares' President, who serves as the qualified person (QP) under the definitions of National Instrument 43-101.

Antares' security, chain of custody and quality control is described on their website under the section on best practices – sampling methodologies.

Mineral resources do not have demonstrated economic viability and future in-fill drilling and scoping, pre-feasibility and feasibility studies will determine what percentage of the inferred resource can be placed into the mineable category. Antares is not aware of any environmental, permitting, legal, title, taxation, socio-political, marketing or other issue which may materially affect this estimate of mineral resources.

Certain disclosure in this release, including management's assessment of Antares' plans and projects, constitutes forward-looking statements that are subject to numerous risks, uncertainties and other factors relating to Antares' operation as a mineral exploration company that may cause future results to differ materially from those expressed or implied. Readers are cautioned not to place undue reliance on forward-looking statements.

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

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