Option agreement (Detail) (Century Thrust Joint Venture Agreement [Member], Century Concession in Laos [Member], USD $)	6 Months Ended	9 Months Ended	12 Months Ended
	Apr. 30, 2012	Jul. 31, 2013	Oct. 31, 2011
Century Thrust Joint Venture Agreement [Member] | Century Concession in Laos [Member]
Mineral Rights [Line Items]
Mining project, option fees paid, capitalized			$ 405,000
Costs associated with mining project, capitalized			20,000
Mining project, exercise price of option		1,350,000
Mining project, write-down of previously capitalized costs	$ 425,000