Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Estimated Useful Lives of Property, Plant and Equipment

Depreciation is calculated using the straight-line method over the estimated useful lives of the property, plant and equipment, which are:


	Years
Land improvements		10
Plant and buildings		5-15
Real estate properties		10-40
Rail spur		30
Vehicles		3-5
Machinery, equipment and tooling		3-15
Furniture and fixtures		3-10
Deferred mining costs		3

Reconciliation of Weighted-Average Common Shares Outstanding Used in the Calculation of Basic Net Income Per Share and Diluted Net Income Per Share

The following table reconciles the weighted-average common shares outstanding used in the calculation of basic net income per share to the weighted average common shares outstanding used in the calculation of diluted net income per share:

	Year Ended December 31,
	2017		2016		2015
Determination of Shares
Weighted average common shares outstanding		40,208		24,322		22,114
Assumed conversion of warrant		-		-		4,000
Assumed conversion of restricted stock		96		257		286
Diluted weighted average common stock outstanding		40,304		24,579		26,400