INTANGIBLE ASSETS: (Tables)

12 Months Ended

Dec. 31, 2012

INTANGIBLE ASSETS:

Schedule of major classes of intangible assets and goodwill

	As of December 31,
(in millions)	2012			2011
Mining concessions	$	121.2		$	121.2
Mine engineering and development studies	6.0			6.0
Software	8.9			7.8
	136.1			135.0
Accumulated amortization	(43.8		)	(41.6		)
Goodwill	17.0			17.0
Intangible assets, net	$	109.3		$	110.4

Schedule of amortization of intangibles in the last three years and estimated amortization for future periods

Amortization of intangibles in the last three years and estimated amortization are as follows (in millions):

Amortization expense:
2012	$	2.2
2011	$	2.1
2010	$	2.1
Estimated amortization expense:
2013-2017	$		10.9
Average annual	$		2.2