7. Income Tax (Details 1) (USD $)	3 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Income Tax Details 1
Federal tax at statutory rate	$ 413,000	$ 292,000
State taxes, net of federal benefit	12,000	9,000
Excess percentage depletion	(203,000)	(135,000)
Other adjustments, net	(5,000)	2,000
Income tax expense	$ 217,000	$ 168,000
Effective rate expressed as a percentage of income before income tax	17.90%	19.50%