CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Operating Activities
Net income	$ 14,793	$ 39,632
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	18,114	16,240
Amortization of deferred financing fees	334	334
Deferred income taxes	7,517	8,698
Stock-based compensation	3,078	4,924
Gain on sale of assets	(269)	(206)
Inventory impairment charge	1,973	0
Other asset impairment charges	8,359	0
Other	(3,786)	(7,405)
Working capital changes:
Affiliates receivable/payable	20	1,903
Accounts receivable	42	8,221
Inventories	(9,361)	(9,256)
Other current assets	(2,582)	1,432
Accounts payable	(10,622)	(388)
Income taxes receivable/payable	(10,790)	(5,447)
Other current liabilities	(19,306)	(5,898)
Net cash (used for) provided by operating activities	(2,486)	52,784
Investing Activities
Expenditures for property, plant and equipment	(30,187)	(24,664)
Acquisition of mineral interests	(14,181)	0
Proceeds from the sale of assets	571	4,572
Purchase of equity securities	(2,000)	0
Other	(187)	(170)
Net cash used for investing activities	(45,984)	(20,262)
Financing Activities
Net additions to revolving credit agreement	14,000	12,000
Additions to long-term debt	7,427	2,000
Reductions to long-term debt	(1,354)	(742)
Cash dividends paid	(5,375)	(5,132)
Purchase of treasury shares	(1,002)	(3,010)
Other	332	(3)
Net cash provided by financing activities	14,028	5,113
Cash and Cash Equivalents
Total (decrease) increase for the year	(34,442)	37,635
Balance at the beginning of the year	122,892	85,257
Balance at the end of the year	$ 88,450	$ 122,892