Segment and Related Information, Segment Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) Segment	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Segment and Related Information [Abstract]
Number of reportable segments | Segment	3
Segment Reporting Information [Abstract]
Net sales	$ 1,858.3	$ 1,594.8	$ 1,791.0
Income from operations	235.7	187.9	208.7
Depreciation, depletion and amortization	94.6	93.9	98.4
Segment assets	3,374.2	3,209.4	3,112.6
Capital expenditures	86.0	66.8	65.0
Segment and Related Information [Abstract]
Litigation expenses	0.0	(10.4)	(10.9)
Acquisition-related expenses	(4.0)	(3.1)	0.0
Unallocated corporate expenses	(7.5)	(10.7)	(8.2)
Consolidated income from operations	235.7	187.9	208.7
Non-operating deductions, net	(33.4)	(49.9)	(51.4)
Income from operations before provision for taxes and equity in earnings	202.3	138.0	157.3
Performance Materials [Member]
Segment Reporting Information [Abstract]
Net sales	976.0	825.8	918.5
Specialty Minerals [Member]
Segment Reporting Information [Abstract]
Net sales	578.9	510.9	574.4
Refractories [Member]
Segment Reporting Information [Abstract]
Net sales	303.4	258.1	298.1
Reportable Segments [Member]
Segment Reporting Information [Abstract]
Net sales	1,858.3	1,594.8	1,791.0
Income from operations	247.2	212.1	227.8
Depreciation, depletion and amortization	94.6	93.9	98.4
Segment assets	3,292.2	3,069.5	3,031.0
Capital expenditures	83.4	66.6	64.9
Segment and Related Information [Abstract]
Consolidated income from operations	247.2	212.1	227.8
Reportable Segments [Member] | Performance Materials [Member]
Segment Reporting Information [Abstract]
Net sales	976.0	825.8	918.5
Income from operations	125.0	108.8	104.9
Depreciation, depletion and amortization	49.2	47.4	51.0
Segment assets	2,393.2	2,219.1	2,212.7
Capital expenditures	22.0	14.6	21.5
Segment and Related Information [Abstract]
Consolidated income from operations	125.0	108.8	104.9
Reportable Segments [Member] | Specialty Minerals [Member]
Segment Reporting Information [Abstract]
Net sales	578.9	510.9	574.4
Income from operations	72.9	67.8	83.1
Depreciation, depletion and amortization	38.4	39.6	40.4
Segment assets	605.9	559.6	525.1
Capital expenditures	51.7	46.5	37.7
Segment and Related Information [Abstract]
Consolidated income from operations	72.9	67.8	83.1
Reportable Segments [Member] | Refractories [Member]
Segment Reporting Information [Abstract]
Net sales	303.4	258.1	298.1
Income from operations	49.3	35.5	39.8
Depreciation, depletion and amortization	7.0	6.9	7.0
Segment assets	293.1	290.8	293.2
Capital expenditures	9.7	5.5	5.7
Segment and Related Information [Abstract]
Consolidated income from operations	49.3	35.5	39.8
Unallocated and Other Corporate Expenses [Member]
Segment Reporting Information [Abstract]
Segment assets	82.0	139.9	81.6
Capital expenditures	$ 2.6	$ 0.2	$ 0.1