Stingray Copper: Metallurgical Update From El Pilar Copper Project, Mexico
TORONTO, ONTARIO–(Marketwire – Sept. 30, 2008) – Peter Mordaunt, CEO and Chairman of Stingray Copper Inc. (“Stingray”) (TSX:SRY)(TSX:SRY.WT) provides an update on the El Pilar metallurgical test work program that is being conducted by Metcon Research Inc. (“Metcon”) at their laboratory facilities in Tucson, Arizona.
The program is a follow up and continuation of the metallurgical test program that had been completed by Noranda Mexico/Falconbridge (“Normex”) with much of Normex’s column leach testing being completed at their Lomas Bayas Copper Mine in Chile.
Stingray completed its program of 207 in fill drill holes at the El Pilar resource in June of 2008. Fifty nine of these drill holes were drilled throughout the resource, specifically for metallurgical work. The drill core material from these drill holes (HQ sized) was then shipped from El Pilar to Metcon’s Tucson laboratory under the direction of the Corporation’s geologists. The metallurgical testing program was designed by Joseph Keane, P.E. on the basis of the anticipated El Pilar mining schedule. Intercepts were identified from the drill holes completed for the metallurgical program. These intercepts correspond to material that would nominally be mined in the annual mine schedule ie: Year 1, Year 2, Year 3, Years 4 to 6 and Years 7 to 9. This resulted in the preparation of five separate drill core composite samples being prepared by Metcon.
These composite samples have been subjected to a series of metallurgical tests completed at the Metcon laboratory as indicated;
– Bottle Roll Leach Tests
– Mini Column Leach Tests
– Open Cycle Column Leach Tests
– Closed Cycle Column Leach Tests
The principal purposes of these tests are;
1. To determine the optimum leaching characteristics that will provide the highest copper extraction from the composite sample.
2. To determine the ultimate sulfuric acid consumption while optimizing the copper extraction from the composite sample.
3. To determine consumable estimates for the heap leaching operations anticipated for each period in the mine schedule.
Many other leaching parameters are determined as part of these tests. These include the crush size of the composite sample (or lack of crushing), pre-curing the composite samples with sulfuric acid (at different acid concentrations), the concentrations of sulfuric acid to be applied during leaching, the flow rates of leaching solutions, the pH levels maintained during the leach test as well as numerous other conditions including the residual condition of the samples post leaching.
The Year 1, Year 2 and Year 3 composite sample test work has been underway since April 2008. The Year 4 to 6 and Year 7 to 9 composite testwork is underway but is not as far advanced as the test work on the first three composite samples. Stingray is provided with regular reports of the test program from Metcon and the following information incorporates results to mid September, 2008.
Results of Bottle Roll Leach Tests
The sequential copper analysis is a fast method for determination of copper species and how they will respond to extraction over short periods of time. The soluble copper at El Pilar is represented by chrysocolla as the dominant copper mineral. Residual copper at El Pilar is a combination of sulfide copper minerals and copper wad, however chalcocite is also present which is an acid soluble copper mineral. This method only identifies acid soluble copper minerals as well as copper sulfides. The results presented below in Table 2 cannot directly determine copper extraction or recovery in the column leach test work or ultimately on the heap leach pad.
__________________ Table 1: El Pilar Bottle Roll Results____________________ ——————————————————————– ——– __________________________________Sequential Copper Analyses ________________________ Head__ —————————— ________________________Grade__ Grade of__ Cyanide______________ Calculated ________________________Total____Soluble__ Soluble__ Residual__ Extractable Resource__ Composite__ Copper____ Copper____Copper____ Copper________Copper Area________ Sample______ (%)________(%)______ (%)________(%)__________ (%) ——————————————————————– ——–
____________________________________________________________________ Pit__________Year 1____ 0.43______ 0.28____ 0.024______0.115________ 76.44 ——————————————————————– ——–
____________________________________________________________________ Pit__________Year 2____ 0.41______ 0.29____ 0.026______0.107________ 75.98 ——————————————————————– ——–
____________________________________________________________________ Pit__________Year 3____ 0.38______ 0.23____ 0.009______0.134________ 70.97 ——————————————————————– ——– Phase 2__ Years 4, 5______________________________________________________ Pit____________ & 6____ 0.31______ 0.18____ 0.009______0.132________ 66.89 ——————————————————————– ——– Ultimate__Years 7, 8______________________________________________________ Pit____________ & 9____ 0.29______ 0.14____ 0.009______0.133________ 58.76 ——————————————————————– ——–
Results of Mini Column Leach Tests
An array of four mini-column leach tests has been completed for each of the Year 1, Year 2 and Year 3 composite samples (the Years 4 to 6 and Years 7 to 9 mini columns are still under leach). For each composite sample, four different pre-cure sulfuric acid dosages was applied (5 day cure period) prior to the column test as follows; 18, 9, 4 and 0 kilograms sulfuric acid per tonne of composite sample. All samples were crushed to 80% passing a 3/8 inch (9.5mm) screen and subject to a sulfuric acid irrigation flow rate of 6.11 liters per hour per square meter.
After completion of the mini-column leaching, Years 1, 2 and 3 composite samples (Starter Pit) indicate copper extractions of 70% or better in all four pre-cure acid dosage conditions as presented in Table 2. Total sulfuric acid consumption ranges from a low of 9.51 to a high of 14.48 kilograms of acid per kilogram of copper extracted.
____Table 2: El Pilar Mini Column Results (Starter Pit; Year 1, 2 and 3) ——————————————————————– ——– ____________Head Grade__ Sulfuric Acid____Leach____Indicated__ Sulfuric Acid Resource________ Total________Pre-Cure____Cycle__ Extraction____ Consumption Area________ Copper %____Dosage (kg/t)__ (Days)____Copper %____kg/ kg Copper ——————————————————————– ——– ____________________________________18______ 98________82.12__________ 12.88 Starter Pit__________________________9______ 98________80.44__________ 10.35 Year 1____________0.43______________ 4______ 98________79.09__________ 10.43 ____________________________________ 0______ 98________79.49____________9.51 ——————————————————————– ——– ——————————————————————– ——– ____________________________________18______ 98________80.88__________ 12.92 Starter Pit__________________________9______ 98________78.47__________ 11.47 Year 2____________0.41______________ 4______ 98________76.65__________ 10.86 ____________________________________ 0______ 98________78.48__________ 10.18 ——————————————————————– ——– ——————————————————————– ——– ____________________________________14______ 98________73.60__________ 14.48 Starter Pit__________________________7______ 98________71.96__________ 13.06 Year 3____________0.38______________ 3______ 98________71.63__________ 12.35 ____________________________________ 0______ 98________71.26__________ 11.84 ——————————————————————– ——–
The mini-column leaching of the Year 4 to 6 and Year 7 to 9 composite samples is underway and is expected to continue through 98 days before the columns are discontinued.
Open Cycle Column Leach Tests: (Crush Size vs Pre-Cure Acid Dosage)
An array of six open cycle column leach tests was established for each of the first 3 composite samples (Starter Pit). For each composite sample a pre-cure dosage of 10 and 0 (no cure) kilograms of sulfuric acid per tonne of composite sample was leached vs three different composite sample crush sizes of 80% passing; 9.5 mm, 19 mm and 37.5 mm or 3/8 inch, 3/4 inch and 1 1/2 inch respectively.
The open cycle column leach testing is expected to continue through a minimum of 130 days before the columns are rinsed, drained and discontinued.
Locked Cycle Column Leach Tests: (Crush Size vs Flow Rate)
An array of four mini-column leach tests was established for each of the first 5 composite samples. Two crush sizes for each composite sample of 80% passing; 9.5 mm and 19 mm or 3/8 inch and 3/4 inch respectively, were leached vs two sulfuric acid irrigation flow rates; 6.11 and 7.80 liters per hour per square meter. All samples were subjected to a 5 day pre-cure of 4 kilograms of sulfuric acid per tonne of composite sample.
The locked cycle column leach testing is expected to continue through a minimum of 120 days before the columns are discontinued.
These results as reported are provided as an interim update of the Corporation’s continuing metallurgical testing program by Metcon. The tests are expected to continue beyond the calendar year end with the necessary conclusions available for incorporation into the ongoing El Pilar technical/feasibility study.
El Pilar Resource
The recently completed in fill drill program (207 drill holes) has resulted in an updated mineral resource calculation completed by Mike Hester of Independent Mining Consultants, Inc. (“IMC”) as reported in the Corporation’s News Release 2008-12. The measured and indicated mineral resource at El Pilar is 199 million tonnes grading 0.35% total copper calculated at a cutoff of 0.25% total copper. At a lower cut-off of 0.20% total copper, the measured and indicated mineral resource is 276 million tonnes grading 0.31% total copper. Stingray’s current work program is designed to establish the mineral reserve and develop the El Pilar as an open pit, heap leach, solvent extraction-electrowinning (SX-EW) copper mine.
Stingray is well financed, with approximately $18M in the treasury, to carry out the current work on the technical/ feasibility study of El Pilar scheduled for completion in Q1 of 2009. Stingray’s experienced engineering team is working along with several third party consultants to complete the necessary work for the study.
Peter Mordaunt, P.Geo is the Qualified Person responsible for the technical content of this release.
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