Anglo American Annual Report 2012

ORE RESERVES AND MINERAL RESOURCES(1)Ore Reserve and Mineral Resource reconciliation categoriesTonnage and content change categoriesOpening BalanceProduction*(from Reserve Model)Depletion*(from Resource Model)ConversionEconomic AssumptionsNew InformationDefinition and explanationas at 31 December – previous reporting yearThe amount of material (expressed in terms of tonnage or content as applicable) removed by planned mining from the scheduled Ore Reservesi.e. the areas actually mined during the reporting period which are removed from the reserve model/s.The amount of material (expressed in terms of tonnage or content as applicable) removed by mining from the Mineral Resources i.e. the areas actuallymined during the reporting period which are removed from the resource model/s. Material removed from the ‘Inferred in Mine Plan’ category should bereported as Depletion.The effect of applying updated ‘Modifying Factors’ to Ore Reserves and Mineral Resources which include geo-technical, mining, metallurgical,marketing, legal, environmental, social and governmental considerations including infrastructure. Includes changes to the mining method, mine planand/or layout changes e.g. changes in pit slope angles or mineable cut due to geo-technical reasons.The change can be positive or negative year-on-year.Sub-Categories:• Conversion is the process of up-grading Mineral Resources to Ore Reserves based on a change in confidence levels and/or modifying factors.• Re-allocation is the process of down-grading of Ore Reserves to Mineral Resources or Mineral Resources to Mineralised Inventory based on a change inconfidence levels and/or modifying factors.• Sterilisation is the process of removing material from Ore Reserves and/or Mineral Resources that no longer has reasonable and realistic prospects foreventual economic extraction.The effect of assumptions based on the current or future price of a commodity and exchange rate estimates as determined by the corporate centre(Global Assumptions) which has a direct impact on the Mineral Resources or Ore Reserves particularly the cut-off grade (which can be affected bychanges in costs).The effect of additional resource definition information (with QA/QC information) which initiates an update to the geological models (facies, structural,grade, geo-technical) and results in an updated (re-classified) resource model and subsequent determination of new Ore Reserve estimates.Includes ore bodies (or portions of current orebodies) within the same project/operation not previously reported.Other Model Refinement No additional resource definition drilling has been undertaken but the interpretation (geometry) of theorebody has been refined or internal mine/lease boundaries changed e.g. based on mappinginformation obtained during mining or a different structural model being applied. Changes to in-situtonnages as a result of new geological losses being applied or a change to the definition of theboundary of the Mineral Resources due to an updated ‘economically mineable cut’ being applied.MethodologyTransferStockpilesNew TechnologyReconciliation AdjustmentOnly valid for changes in the estimation or classification methodologies applied to the resource modelevaluation i.e. no new information available or model refinement taken place.Movement of Mineral Resources and/or Ore Reserves from one type of product/ore type to another orfrom one mining/project area to another.Changes to stockpiles.Changes to Mineral Resources or Ore Reserves in response to the application of new or improvedmining and/or processing methods.Changes which cannot be allocated to a defined category or an adjustment necessary to mitigateinaccurate production/depletion estimates of the previous year.*AcquisitionsDisposalsClosing BalanceAdditional Mineral Resources and Ore Reserves due to acquisitions of assets or increased attributable interests in JV agreements/associate companies.Reduction in Mineral Resources and Ore Reserves due to disposals of assets or reduced attributable interests in JV agreements/associate companies,refusal/withdrawal of Mining/Prospecting Rights or related permits e.g. due to environmental issues, changes in policy.as at 31 December – current reporting year* The Production/Depletion figures may be estimated for these last three months of the reporting period based on the monthly average of the previous nine months.(2)Ore Reserves: Includes Proved and ProbableMineral Resources: Includes Measured, Indicated and Inferred [for Coal only Inferred (in LOM Plan) is considered]Due to the uncertainty that may be attached to some Inferred Mineral Resources, it cannot be assumed that all or part of an Inferred Mineral Resource will necessarily be upgraded to an Indicated orMeasured Resource after continued exploration.Rounding of figures may cause computational discrepancies.Ore Reserves and Mineral ResourcesAnglo American plc Annual Report 2012 227