Intangible assets acquired as part of a business combination, other than goodwill, are initially measured at their  fair value at the date of the acquisition. Intangible assets acquired separately are initially recognised at cost.  Indefinite life intangible assets are not amortised and are subsequently measured at cost less any impairment.  Finite life intangible assets are subsequently measured at cost less amortisation and any impairment. The gains  or losses recognised in profit or loss arising from the derecognition of intangible assets are measured as the  difference between net disposal proceeds and the carrying amount of the intangible asset. The method and useful  lives of finite life intangible assets are reviewed annually. Changes in the expected pattern of consumption or  useful life are accounted for prospectively by changing the amortisation method or period. Goodwill arises on the acquisition of a business. Goodwill is not amortised. Instead, goodwill is tested annually for  impairment, or more frequently if events or changes in circumstances indicate that it might be impaired, and is  carried at cost less accumulated impairment losses. Impairment losses on goodwill are taken to profit or loss and  are not subsequently reversed. Notes to the  Financial  Statements For personal use only Operating leases Patents and trademarks Goodwill Port access rights INTANGIBLE ASSETS EXPLORATION AND EVALUATION ASSETS DEVELOPMENT EXPENDITURES 58 Mineral Resources Limited Annual Report 2014 Depreciation is charged using the units-of-production method, with separate calculations being made for each  area of interest. The units-of-production basis results in a depreciation charge proportional to the depletion of  proved, probable and estimated reserves. Development properties are tested for impairment in accordance with  the policy on impairment of assets. A development property is reclassified as a mining property at the end of the commissioning phase, when the  mine is capable of operating in the manner intended by management. Once a development decision has been taken, the carrying amount of the exploration and evaluation expenditure  in respect of the area of interest is aggregated with the development expenditure and classified under non-current  assets as development properties. Development expenditure incurred by or on behalf of the Consolidated Entity is accumulated separately for each  area of interest in which economically recoverable resources have been identified. Such expenditure comprises  cost directly attributable to the construction of a mine and the related infrastructure. Exploration and evaluation expenditure in relation to separate areas of interest for which rights of tenure  are current is carried forward as an asset in the statement of financial position where it is expected that the  expenditure will be recovered through the successful development and exploitation of an area of interest, or by  its sale; or exploration activities are continuing in an area and activities have not reached a stage which permits  a reasonable estimate of the existence or otherwise of economically recoverable reserves. Where a project or  an area of interest has been abandoned, the expenditure incurred thereon is written off in the year in which the  decision is made. Operating leases acquired as part of a business combination are recognised separately from goodwill. The leases  are carried at their fair value at the date of acquisition less accumulated amortisation and impairment losses.  Amortisation is calculated based on the timing of projected cash flows of the lease over their estimated useful lives. Port access rights acquired as part of a business combination are recognised separately from goodwill. The rights  are carried at their fair value at the date of acquisition less accumulated amortisation and impairment losses.  Amortisation is calculated based on the timing of projected cash flows of the access rights over their estimated  useful lives. Significant costs associated with patents and trademarks are deferred and amortised on a straight-line basis over  the period of their expected benefit. 30 June 2014 Notes to the Financial Statements