CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
OPERATING ACTIVITIES:
Net income	$ 11,161	$ 10,900
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	8,404	8,572
Amortization of deferred financing costs	6	15
Deferred income taxes	2,619	1,157
Loss on disposition of property, plant and equipment	97	345
Stock-based compensation	691	713
Changes in operating assets and liabilities:
Trade receivables, net	(3,344)	(4,450)
Inventories, net	517	1,289
Prepaid expenses and other current assets	341	438
Other assets	50	93
Accounts payable and accrued expenses	(452)	(697)
Other liabilities	(54)	(145)
Net cash provided by operating activities	20,036	18,230
INVESTING ACTIVITIES:
Purchase of property, plant and equipment	(12,360)	(19,378)
Proceeds from sale of property, plant and equipment	461	183
Net cash used in investing activities	(11,899)	(19,195)
FINANCING ACTIVITIES:
Cash dividends paid	(1,517)	(1,511)
Proceeds from exercise of stock options	75	73
Purchase of treasury shares	(241)	(251)
Net cash used in financing activities	(1,683)	(1,689)
Net increase (decrease) in cash and cash equivalents	6,454	(2,654)
Cash and cash equivalents at beginning of period	67,218	85,000
Cash and cash equivalents at end of period	$ 73,672	$ 82,346