CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND RETAINED EARNINGS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND RETAINED EARNINGS
Net sales	$ 31,987	$ 23,965	$ 79,773	$ 72,932
Type of Revenue [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Costs and expenses:
Cost of sales (exclusive of depreciation, depletion and amortization)	$ 24,452	$ 18,740	$ 63,834	$ 56,728
Depreciation, depletion and amortization	597	393	1,369	1,203
Selling and administrative	8,102	6,100	23,991	15,938
Charges related to write-off of deferred development				6,840
Impairment related to cessation of mining an aggregate deposit	20,217		20,217
Loss on legal settlement (Note 20)	6,400		6,400
Gain on legal settlement (Note 14)			(14,781)
Gain (loss) on disposition of property and equipment	125		(308)
Total costs and expenses	59,893	25,233	100,722	80,709
Operating loss	(27,906)	(1,268)	(20,949)	(7,777)
Interest income	39	14	349	59
Interest expense	(100)	(140)	(274)	(415)
Other income (loss), net	(16)	(70)	42	(29)
Loss from continuing operations before income taxes	(27,983)	(1,464)	(20,832)	(8,162)
Benefit for income taxes	(7,699)	(366)	(5,730)	(2,040)
Net loss from continuing operations	(20,284)	(1,098)	(15,102)	(6,122)
(Loss) Income from discontinued operations net of income tax (benefit) provision		(138)	3,304	806
Net loss	(20,284)	(1,236)	(11,798)	(5,316)
Retained earnings, beginning of period	69,617	62,907	61,131	66,987
Retained earnings, end of period	$ 49,333	$ 61,671	$ 49,333	$ 61,671
Basic and diluted loss per share:
Loss from continuing operations	$ (11.85)	$ (0.65)	$ (8.82)	$ (3.61)
(Loss) income from discontinued operations		(0.08)	1.93	0.47
Basic and diluted (loss) income per share (in dollar per share)	$ (11.85)	$ (0.73)	$ (6.89)	$ (3.13)
Average shares outstanding (in shares)	1,712	1,698	1,712	1,697