Feb 22 2013
Belo Sun Mining Corp. has received positive results from the ongoing metallurgical test work program for its 100% owned Volta Grande Gold Project located in Para State, Brazil. The metallurgical test work program returned an average recovery of 94%.
The program was focused on the diorite gold-bearing material of the Grota Seca (GS) and Ouro Verde (OV) ore bodies which make up the Volta Grande Project. The purpose of the metallurgical test work program was to complete various grind determination and gold recovery tests in order to determine the best process flow sheet and economic parameters for use in the upcoming feasibility studies. The metallurgical test work program was designed to test the variability of GS and OV ores under different process conditions. Samples collected for this metallurgical test work program were selected from drill core samples.
For the gold recovery tests, medium and high grade composites were prepared with varying gold head grades from approximately 1 g/t to 4 g/t from each of the GS and OV ore bodies.
The following tests made up the gold recovery section of the metallurgical test work program:
- Chemical characterization, size distribution and DRX analysis of the head samples.
- Preg-robbing tests.
- Gravity separation tests using centrifugal concentrators.
- Leaching tests under different conditions including grind size, slurry density, cyanide concentration and dissolved oxygen concentration.
The highlights of the gold recovery tests included:
- Between 25% to 50% of the gold can be recovered in a gravity concentration step prior to leaching.
- The optimal leaching conditions for the OV and GS composites were a grind size of 80% passing 75 micrometres, slurry density of 50% by weight, 0.5 g/L NaCN concentration, 10 ppm dissolved oxygen concentration at a pH of 10.5.
- For the OV ore, with a gold head grade varying between 1.17 g/t to 3.80 g/t, with an average gold recovery of 94%.
- For the GS ore, with a gold head grade varying between 1.06 g/t to 3.90 g/t, with an average gold recovery of 94%.
- The OV and GS ores are amenable to conventional gravity and gold leaching processes including leach / CIP or CIL.
A series of nine composites were collected for the grinding test work. These composites were collected such that they represented the main lithology groups found in the OV and GS ore bodies.
The following tests made up the grind determination section of the metallurgical test work program:
- SAG Mill Comminution Test (DWi and A x b).
- SAG Power Index Test (SPI).
- Bond Abrasion Index Test (Ai).
- Rod Bond Work Index Test (RMWi).
- Bond Ball Work Index Test (BMWi).
The highlights of the grind determination tests included the following:
- The average results obtained from the grinding determination tests were DWi = 10.2 kWh/m3, A x b = 27.8, SPI = 163.2 minutes, Ai = 0.39, RMWi = 14.48 kWh/st and the BMWi = 14.01 kWh/st.
- These results indicate that the OV and GS ores are amenable to conventional primary crushing, SAG and ball milling.
Omar Antunes, Metallurgy Manager for the Volta Grande Project, commented: "These metallurgical results are confirming previous test work, with excellent gold recoveries for our planned processing plant as well as confirming a simple, conventional, robust, environmentally safe and straightforward low cost process route to support feasibility studies. We are pleased to be able to report such excellent results for both deposits."
Ian Pritchard, Chief Operating Officer of Belo Sun, said "The testwork results confirm earlier work and provides Belo Sun with the parameters for finalising the plant design as we move towards the completion of the feasibility studies."
The results reported in this news release are from test work performed in Santiago Chile by SGS Minerals S.A, Chile. The test work was directly supervised by Sebastián Bravo, process supervisor and by Catherine Souza, head engineer in charge of the Volta Grande Project. SGS Technical Manager Dr. Heriban Soto, coordinated the laboratory work.
The test results reported have been reviewed by Omar Antunes, Metallurgy Manager for the Volta Grande Project.
David Evans, P.Eng., an independent consultant to the Company and a Qualified Person under NI 43-101, has reviewed the scientific and technical information in this release.