Goodwill and Other Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2018

Goodwill and Other Intangible Assets [Abstract]

Carrying amount of goodwill by reportable segment

The balance of goodwill by segment and the activity occurring in the past two fiscal years is as follows:

(millions of dollars)	Performance Materials		Specialty Minerals			Refractories			Consolidated
Balance at December 31, 2016	$	720.9	$	12.1		$	45.7		$	778.7
Change in goodwill relating to:
Foreign exchange translation		—		0.6			—			0.6
Total Changes	$	—	$	0.6		$	—		$	0.6
Balance at December 31, 2017	$	720.9	$	12.7		$	45.7		$	779.3
Change in goodwill relating to:
Acquisition of Sivomatic		35.0		—			—			35.0
Foreign exchange translation		—		(0.4	)		(1.5	)		(1.9	)
Total Changes	$	35.0	$	(0.4	)	$	(1.5	)	$	33.1
Balance at December 31, 2018	$	755.9	$	12.3		$	44.2		$	812.4

Acquired intangible assets subject to amortization

Acquired intangible assets subject to amortization as of December 31, 2018 and December 31, 2017 were as follows:

			December 31, 2018				December 31, 2017
	Weighted Average Useful Life (Years)		Gross Carrying Amount		Accumulated Amortization		Gross Carrying Amount		Accumulated Amortization
Tradenames		35	$	204.2	$	26.6	$	199.8	$	20.7
Technology		13		18.8		6.4		18.8		4.8
Patents		19		6.4		5.6		6.4		5.3
Customer relationships		22		26.5		3.2		4.5		2.2
		32	$	255.9	$	41.8	$	229.5	$	33.0