Significant accounting judgments and estimates	12 Months Ended
Dec. 31, 2017
Significant accounting judgments and estimates [abstract]
Significant accounting judgments and estimates	4. Significant accounting judgments and estimates The preparation of financial statements in conformity with IFRS requires management to make judgments and estimates that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The areas which require management to make significant judgments, estimates and assumptions in determining carrying values include, but are not limited to: (i) Reserves and resources Proven and probable reserves are the economically mineable parts of the Company’s measured and indicated mineral resources. The Company estimates its proven and probable reserves and measured and indicated and inferred mineral resources based on information compiled by appropriately qualified persons. The information relating to the geological data on the size, depth and shape of the ore bodies requires complex geological judgments to interpret the data. The estimation of future cash flows related to proven and probable reserves is based upon factors such as estimates of foreign exchange rates, commodity prices, future capital requirements and production costs along with geological assumptions and judgments made in estimating the size, grade and recovery of the ore bodies. Changes in the proven and probable reserves or measured, indicated and inferred mineral resources estimates may impact the carrying value of mining properties and equipment, depletion and amortization, impairment assessments and the timing of decommissioning provisions. (ii) Depletion and amortization Mining properties are depleted using the unit-of-production method over a period not to exceed the estimated life of the ore body based on estimated recoverable reserves. Property, plant and equipment are depreciated, net of residual value over their estimated useful life but do not exceed the related estimated life of the mine based on estimated recoverable mineral reserves. The calculation of the units of production rate, and therefore the annual depletion and amortization expense, could be materially affected by changes in the underlying estimates. Changes in estimates can be the result of actual future production differing from current forecasts of future production and expansion of mineral reserves through exploration activities. Significant judgment is involved in the determination of useful life and residual values for the computation of depletion and amortization. No assurance can be given that actual useful lives and residual values will not differ significantly from current assumptions. (iii) Decommissioning provision The Company assesses its decommissioning provision on an annual basis or when new material information becomes available. Mining and exploration activities are subject to various laws and regulations governing the protection of the environment. In general, these laws and regulations are continually changing and the Company has made, and intends to make in the future, expenditures to comply with such laws and regulations. Accounting for decommissioning provision requires management to make estimates of the time and future costs the Company will incur to complete the rehabilitation work required to comply with existing laws and regulations at each mining operation. Also, future changes to environmental laws and regulations could increase the extent of rehabilitation work required to be performed by the Company. Increases in future costs could materially impact the amounts charged to operations for decommissioning provision. The provision represents management’s best estimate of the present value of the future decommissioning provision. The actual future expenditures may differ from the amounts currently provided. (iv) Share-based payments The amount expensed for share-based compensation is based on the application of a recognized option valuation formula, which is highly dependent on, amongst other things, the expected volatility of the Company’s registered shares, estimated forfeitures, and the expected life of the options. The Company uses an expected volatility rate for its shares based on past stock trading data, adjusted for future expectations, and actual volatility may be significantly different. The resulting value calculated is not necessarily the value that the holder of the option could receive in an arm’s length transaction, given that there is no market for the options and they are not transferable. It is management’s view that the value derived is highly subjective and dependent entirely upon the input assumptions made. (v) Income taxes Preparation of the consolidated financial statements requires an estimate of income taxes in each of the jurisdictions in which the Company operates. The process involves an estimate of the Company’s current tax exposure and an assessment of temporary differences resulting from differing treatment of items, such as depletion and amortization, for tax and accounting purposes, and when they might reverse. These differences result in deferred tax assets and liabilities that are included in the Company’s consolidated statements of financial position. An assessment is also made to determine the likelihood that the Company’s future tax assets will be recovered from future taxable income. To the extent that recovery is not considered likely, the related tax benefits are not recognized. Judgment is required to continually assess changing tax interpretations, regulations and legislation, to ensure liabilities are complete and to ensure assets, net of valuation allowances, are realizable. The impact of different interpretations and applications could be material. (vi) Commercial production The determination of timing on which a mining property enters into commercial production is a significant judgment since capitalization of development costs ceases and revenue recognition begins upon declaration of commercial production. As a mining property is constructed, development costs incurred are capitalized while pre-production costs and revenues are capitalized and accumulated into such development costs. Commercial production is declared once the mining property is available for its intended use on a commercial scale as defined by management. Revenue recognition and depletion of the mining property begins when commercial production has been achieved.

4. Significant accounting judgments and estimates

The preparation of financial statements in conformity with IFRS requires management to make judgments and estimates that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

The areas which require management to make significant judgments, estimates and assumptions in determining carrying values include, but are not limited to:

(i) Reserves and resources

Proven and probable reserves are the economically mineable parts of the Company’s measured and indicated mineral resources. The Company estimates its proven and probable reserves and measured and indicated and inferred mineral resources based on information compiled by appropriately qualified persons. The information relating to the geological data on the size, depth and shape of the ore bodies requires complex geological judgments to interpret the data. The estimation of future cash flows related to proven and probable reserves is based upon factors such as estimates of foreign exchange rates, commodity prices, future capital requirements and production costs along with geological assumptions and judgments made in estimating the size, grade and recovery of the ore bodies.

Changes in the proven and probable reserves or measured, indicated and inferred mineral resources estimates may impact the carrying value of mining properties and equipment, depletion and amortization, impairment assessments and the timing of decommissioning provisions.

(ii) Depletion and amortization

Mining properties are depleted using the unit-of-production method over a period not to exceed the estimated life of the ore body based on estimated recoverable reserves.

Property, plant and equipment are depreciated, net of residual value over their estimated useful life but do not exceed the related estimated life of the mine based on estimated recoverable mineral reserves.

The calculation of the units of production rate, and therefore the annual depletion and amortization expense, could be materially affected by changes in the underlying estimates. Changes in estimates can be the result of actual future production differing from current forecasts of future production and expansion of mineral reserves through exploration activities.

Significant judgment is involved in the determination of useful life and residual values for the computation of depletion and amortization. No assurance can be given that actual useful lives and residual values will not differ significantly from current assumptions.

(iii) Decommissioning provision

The Company assesses its decommissioning provision on an annual basis or when new material information becomes available. Mining and exploration activities are subject to various laws and regulations governing the protection of the environment. In general, these laws and regulations are continually changing and the Company has made, and intends to make in the future, expenditures to comply with such laws and regulations. Accounting for decommissioning provision requires management to make estimates of the time and future costs the Company will incur to complete the rehabilitation work required to comply with existing laws and regulations at each mining operation. Also, future changes to environmental laws and regulations could increase the extent of rehabilitation work required to be performed by the Company. Increases in future costs could materially impact the amounts charged to operations for decommissioning provision. The provision represents management’s best estimate of the present value of the future decommissioning provision. The actual future expenditures may differ from the amounts currently provided.

(iv) Share-based payments

The amount expensed for share-based compensation is based on the application of a recognized option valuation formula, which is highly dependent on, amongst other things, the expected volatility of the Company’s registered shares, estimated forfeitures, and the expected life of the options. The Company uses an expected volatility rate for its shares based on past stock trading data, adjusted for future expectations, and actual volatility may be significantly different.

The resulting value calculated is not necessarily the value that the holder of the option could receive in an arm’s length transaction, given that there is no market for the options and they are not transferable. It is management’s view that the value derived is highly subjective and dependent entirely upon the input assumptions made.

(v) Income taxes

Preparation of the consolidated financial statements requires an estimate of income taxes in each of the jurisdictions in which the Company operates. The process involves an estimate of the Company’s current tax exposure and an assessment of temporary differences resulting from differing treatment of items, such as depletion and amortization, for tax and accounting purposes, and when they might reverse.

These differences result in deferred tax assets and liabilities that are included in the Company’s consolidated statements of financial position.

An assessment is also made to determine the likelihood that the Company’s future tax assets will be recovered from future taxable income. To the extent that recovery is not considered likely, the related tax benefits are not recognized.

Judgment is required to continually assess changing tax interpretations, regulations and legislation, to ensure liabilities are complete and to ensure assets, net of valuation allowances, are realizable. The impact of different interpretations and applications could be material.

(vi) Commercial production

The determination of timing on which a mining property enters into commercial production is a significant judgment since capitalization of development costs ceases and revenue recognition begins upon declaration of commercial production. As a mining property is constructed, development costs incurred are capitalized while pre-production costs and revenues are capitalized and accumulated into such development costs. Commercial production is declared once the mining property is available for its intended use on a commercial scale as defined by management. Revenue recognition and depletion of the mining property begins when commercial production has been achieved.