«COMPAÑIA MINERA ANTAMINA S.A. ANNOUNCES UPDATED MINERAL RESOURCE AND ORE RESERVE ESTIMATES»
Compañia Minera Antamina S.A. (“Antamina”) announced today an 18% increase to 822 million tonnes to the Ore Reserve estimate for the Antamina deposit as of January 1, 2011. Mineral Resources have also increased significantly from the previous estimates of January 1, 2010 (Table 3 and Table 4).
The new Ore Reserve estimate as of January 1, 2011 represents an increase of approximately 123 million tonnes of Ore Reserve compared to the previous Ore Reserve estimate dated January 1, 2010. Contained copper in the Ore Reserve has increased by 5% and contained zinc has increased by 24%.
The increase in the Ore Reserve and Mineral Resource is a result of the inclusion of data obtained from over 155,000 meters of additional core drilling performed from October 2007 through November 2008, the updated long term metal price assumptions and the subsequent pit optimization process. This work has resulted in a new open pit design and mine production schedule.
“The latest Mineral Resource and Ore Reserve upgrade at Antamina reflect the world class scale and quality of the growing Mineral Resource base at Antamina,” said the Compañia Minera Antamina Chief Executive Officer Mr Abraham Chahuan.
Table 1 shows the updated Ore Reserves, and Table 2 shows the previous Ore Reserve estimate.
Table 1: Ore Reserve Estimate as of January 1, 2011
| Classification | Tonnes (Millions) | Cu (%) | Zn(%) | Ag(g/t) | Mo(%) |
| Proved Copper Sulphide | 100 | 1.07 | 0.16 | 8.3 | 0.034 |
| Proved Copper Zinc Sulphide | 47 | 0.84 | 1.83 | 15.0 | 0.007 |
| Probable Copper Sulphide | 492 | 0.95 | 0.14 | 8.9 | 0.027 |
| Probable Copper Sulphide | 183 | 0.83 | 2.00 | 14.5 | 0.006 |
| Total Proved and Probable Ore Reserves | 822 | 0.93 | 0.66 | 10.4 | 0.022 |
Table 2. Previous Ore Reserve Estimate as of January 1, 2010
| Classification | Tonnes (Millions) | Cu (%) | Zn(%) | Ag(g/t) | Mo(%) |
| Proved Copper Sulphide | 82 | 1.08 | 0.17 | 8.4 | 0.037 |
| Proved Copper Zinc Sulphide | 37 | 0.90 | 2.17 | 18.3 | 0.008 |
| Probable Copper Sulphide | 445 | 1.05 | 0.17 | 9.7 | 0.031 |
| Probable Copper Sulphide | 135 | 1.06 | 1.99 | 17.5 | 0.008 |
| Total Proved and Probable Ore Reserves | 699 | 1.04 | 0.62 | 11.5 | 0.026 |
Table 3 below shows the updated Antamina Mineral Resource estimate; Table 4 below shows the previous resource estimate. The Measured and Indicated Mineral Resources reported in Table 3 and 4 below are additional to the Ore Reserves.
Table 3: Incremental Mineral Resource as of January 1, 2011 (*)
| Classification | Tonnes (Millions) | Cu (%) | Zn(%) | Ag(g/t) | Mo(%) |
| Measured Copper Sulphide | 35 | 0.46 | 0.12 | 4.6 | 0.037 |
| Measured Copper Zinc Sulphide | 15 | 0.46 | 0.85 | 9.1 | 0.024 |
| Indicated Copper Sulphide | 276 | 0.93 | 0.12 | 9.2 | 0.023 |
| Indicated Copper Zinc Sulphide | 78 | 0.87 | 1.90 | 12.6 | 0.006 |
| Total Measured and Indicated Mineral Resources | 404 | 0.86 | 0.49 | 9.6 | 0.021 |
| Inferred Copper Sulphide | 531 | 0.79 | 0.11 | 9.2 | 0.018 |
| Inferred Copper Zinc Sulphide | 177 | 0.54 | 1.33 | 9.7 | 0.003 |
| Total Inferred Mineral Resources | 708 | 0.73 | 0.42 | 9.3 | 0.014 |
Table 4: Previous Incremental Mineral Resource as of January 1, 2010 (*)
| Classification | Tonnes (Millions) | Cu (%) | Zn(%) | Ag(g/t) | Mo(%) |
| Measured Copper Sulphide | 30 | 0.49 | 0.12 | 4.8 | 0.041 |
| Measured Copper Zinc Sulphide | 14 | 0.48 | 0.85 | 9.6 | 0.026 |
| Indicated Copper Sulphide | 126 | 0.83 | 0.14 | 8.0 | 0.022 |
| Indicated Copper Zinc Sulphide | 21 | 1.09 | 1.40 | 14.8 | 0.010 |
| Total Measured and Indicated Mineral Resources | 190 | 0.78 | 0.33 | 8.3 | 0.024 |
| Inferred Copper Sulphide | 487 | 0.83 | 0.13 | 9.7 | 0.017 |
| Inferred Copper Zinc Sulphide | 93 | 0.86 | 1.60 | 15.7 | 0.006 |
| Total Inferred Mineral Resources | 580 | 0.84 | 0.37 | 10.7 | 0.015 |
* The Measured and Indicated Mineral Resources reported in Table 3 and 4 above are additional to the Ore Reserves
Compañía Minera Antamina is a joint venture company held indirectly as to 33.75% by BHP Billiton Ltd., 33.75% by Xstrata plc, 22.5% by Teck Resources Limited and 10% by Mitsubishi Corporation.
The following notes apply to the new Ore Reserves estimate:
(1) This report complies with the Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves (the JORC Code) and with the requirements of the CIM Definition Standards for Mineral Resources and Mineral Reserves (CIM Definition Standards 2005).
(2) Ore Reserves, as defined under the JORC Code are equivalent to Mineral Reserves as defined under National Instrument 43-101. “Proved” Ore Reserves as defined under the JORC Code are equivalent to “Proven” Mineral Reserves as defined under National Instrument 43-101.
(3) The Ore Reserve estimate is the result of a life-of-mine plan that considered only Measured and Indicated Mineral Resource categories. The following assumed long term metal prices were applied in developing the reserve estimate, life-of-mine plan and resource estimate: Copper $1.99/lb, Zinc $0.87/lb, Molybdenum $10.19/lb and Silver $10.18/oz. The life-of-mine plan was optimized using variable cut-off grades; so there is not a single cut-off grade applied to the reserve estimate.
(4) The information in this press release that relates to the Antamina Ore Reserves is based on information compiled by Mr. Luis Lozada who is employed by Compañía Minera Antamina, is a Member of The Australasian Institute of Mining and Metallurgy and has sufficient experience relevant to the style of mineralization and type of deposit under consideration and to the activity which he is undertaking. As such, he is qualified as a Competent Person as defined in the 2004 Edition of the JORC Code and a Qualified Person as defined in CIM Definition Standards 2005. Mr. Lozada consents to the inclusion in this press release of the matters based on his information in the form and context in which it appears.
The following note applies to the Mineral Resource estimate:
(1) The information in the report to which this statement is attached that relates to Mineral Resources is based on information compiled by Jhon Espinoza, who is an employee of BHP Billiton, is a Member of The Australasian Institute of Mining and Metallurgy and was an employee of Compañia Minera Antamina for more than 11 years. Mr. Espinoza has sufficient experience which is relevant to the style of mineralisation and type of deposit under consideration and to the activity which he is undertaking to qualify as a Competent Person as defined in the 2004 Edition of the ‘Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves’ and a Qualified Person as defined in CIM Definition Standards 2005. Mr. Espinoza consents to the inclusion in this press release of the matters based on his information in the form and context in which it appears.
For additional information, please contact:
Amalia Ruiz, Manager Corporate Communications
Telephone: 511-217-3092 Fax: 511-217-3095
Email: aruiz@antamina.com
