By Darryl Kelley
After a long wait of over 5 years, Vannessa Ventures (TSX.V:VVV) has received final confirmation from the Costa Rican Mining Ministry (MINAE) authorizing the exploitation of the Crucitas project by Vannessa. This clears the way for construction to begin immediately.
Industrias Infinito S.A. ("Infinito"), a wholly owned subsidiary of Vannessa Ventures Ltd. has received an official news release from MINAE dated April 23, 2008 that states the Government of the Republic of Costa Rica authorizes the exploitation of the Crucitas concession as environmental, social and economic feasibility has been demonstrated.
This follows the Company's announcement of April 16, 2008 where it was reported that the minister in charge of MINAE had indicated to the local media that the Crucitas project would be approved soon. This authorization, together with the approval of the EIS, represents the final major approvals required by the Company in order to advance the development of the Crucitas gold project.
In a newspaper article in La Nacion, published on April 24, 2008, it was announced that MINAE had lifted the moratorium on open pit gold mining in the country which has been in place since 2002. The moratorium did not apply to the Crucitas exploitation concession but the removal is a positive action that will increase the potential of the more than 18,000 hectares of exploration concessions held by Infinito adjacent to the Crucitas project area.
Vannessa has an feasibility report by Micon International on the Crucitas project completed in February of 2007.
The feasibility study provides a description of the geology, mining and milling operations, tailings facilities, services and other facilities, together with the associated capital and operating costs, required to develop the Crucitas Project. The study includes description of the mining plan and mine operations, processing requirements, the tailings and water management systems, the necessary site infrastructure and presents the environmental, permitting and socio-economic considerations in undertaking the project.
The total Indicated Resources above the 0.5 g Au/t cut-off grade are estimated to contain
25.1 millions tonnes at 1.22 g Au/t (985 thousand gold ounces) and at 3.17 g Ag/t (2.56
million silver ounces) in both Fortuna and Botija in and out of the structures, as shown below.
Estimated Indicated Mineral Resources at Crucitas
Material/Zone Tonnes Gold (g/t) Silver (g/t) Gold oz Silver oz
Saprolite
Total Structure 3,528,630 1.6 1.91 181,22 217,052
Total Outvein 638,472 0.64 1.00 13,224 20,443
Total Saprolite 4,167,102 1.45 1.77 194,646 237,495
Rock
Total Structure 16,540,075 1.32 3.51 700,919 1,863,994
Total Outvein 4,378,546 0.63 3.25 89,376 457,617
Total Rock 20,918,621 1.18 3.45 790,295 2,321,611
Total 25,085,723 1.22 3.17 984,941 2,559,105
The total Inferred Resources above the 0.5 g Au/t cut-off grade are estimated to contain 12.6 millions tonnes at 1.23 g Au/t (496 thousand gold ounces) and at 3.14 g Ag/t (1.27 million silver ounces) in the Inferred category for Fortuna, Botija and Fuentes in and out of the structures, as shown in Table 1.2.
Estimated Inferred Resources
Material/Zone Tonnes Gold (g/t) Silver (g/t) Gold oz Silver oz
Saprolite
Total Structure 2,261,899 1.48 2.75 107,707 199,698
Total Outvein 721,185 0.69 1.02 16,065 23,566
Total Saprolite 2,983,084 1.29 2.33 123,722 223,265
Rock
Total Structure 7,081,264 1.42 3.52 322,579 801,190
Total Outvein 2,502,871 0.62 3.02 49,721 243,025
Total Rock 9,584,135 1.12 3.39 372,300 1,044,215
Total 12,567,219 1.23 3.14 496,072 1,267,479
Mining will be by the open pit method with conventional shovel and truck operations. The open-pit optimization for the Los Crucitas project was carried out using the Geostat mineral resource block model and Surpac Lerchs-Grossman pit optimization software.
The mining will be conducted on 5 metre benches, with a pre-strip totalling 440,000 cubic metres, planned to gain barren saprolite waste to be used in construction of the tailings dam. After ramping up to plant capacity, a nominal plant feed consisting of a blend of 75% saprolite and 25% hard rock, is planned to continue until the completion of the saprolite reserves.
The plant capacity is designed for 7,500 ore tonnes per day (2.50 Mtpa) within saprolite, whereas within hard rock the plant capacity is 5,000 tonnes per day (1.82 Mtpa).
Therefore an initial ore production rate from the mine of 6,875 tonnes per day was scheduled in order to provide the nominal feed of 75% saprolite and 25% hard rock. On completion of the saprolite reserves the plant feed rate will be reduced and so the ore production rate is dropped to 5,000 tonnes per day.
There is capacity for the stockpiling of 50,000 tonnes of hard rock ore, which can be stored on a pad adjacent to the plant. The planned strip ratio during mine production was 1.35, and is maintained as closely as possible throughout the mine life. At the earliest date possible, waste is planned to be back-filled into completed sections of the mine.
The production schedule is planned around a work regime of 350 days per annum and 20 hours per day. In order to minimize dilution and mining losses, ore excavations are scheduled for the day shifts.
The majority of metallurgical testing on Las Crucitas samples was conducted in four phases by Placer Dome International (PDI) during development of the previous feasibility study completed by Cambior in 1999. In 2005, additional testing by Process Research Associates was commissioned to confirm leaching characteristics and test the use of oxygen. CyPlus also carried out further work to determine cyanide destruction parameters, and a further review of all testing was conducted
The gold extraction testwork confirmed that the ore is readily amenable to agitated cyanidation, at an optimum grind size of 150 microns. The low levels of silver and its limited recovery through cyanidation, the absence of deleterious elements consuming cyanide, and robbing the pregnant solution of the dissolved gold favour a treatment scheme with a CIP process. Whole ore cyanidation provides comparable results to the optimum results obtained with a more complex gravity plus cyanidation process, and without requiring significantly more leaching residence time.
