Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2015

Property and equipment and depreciation - We state property and equipment at cost, including capitalized interest on borrowings during the actual construction period of major capital projects. Capitalized interest costs were $1.5 million in 2013, $2.9 million in 2014 and $1.1 million in 2015. We compute depreciation of property and equipment for financial reporting purposes (including mining equipment) principally by the straight-line method over the estimated useful lives of the assets as follows:

Asset		Useful lives
Buildings and improvements		10 to 40 years
Machinery and equipment		3 to 20 years
Mine development costs		units-of-production