CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS Percentage	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenues
Lime and limestone operations (as a percent)	98.20%	98.70%
Natural gas interests (as a percent)	1.80%	1.30%
Total revenues (as a percent)	100.00%	100.00%
Cost of revenues:
Labor and other operating expenses (as a percent)	65.50%	65.00%
Depreciation, depletion and amortization (as a percent)	11.70%	11.60%
Total cost of revenues (as a percent)	77.20%	76.60%
Gross profit (as a percent)	22.80%	23.40%
Selling, general and administrative expenses (as a percent)	6.70%	7.20%
Operating profit (as a percent)	16.10%	16.20%
Other expenses (income):
Interest expense (as a percent)	0.20%	0.10%
Other income, net (as a percent)	(0.50%)	(0.10%)
Total other expense (income) (as a percent)	(0.30%)	0.00%
Income before income taxes (as a percent)	16.40%	16.20%
Income tax expense (as a percent)	3.60%	4.10%
Net income (as a percent)	12.80%	12.10%