Option agreement (Detail) (Century Thrust Joint Venture Agreement, Century Concession in Laos, USD $)	6 Months Ended	12 Months Ended
	Apr. 30, 2013	Oct. 31, 2012	Oct. 31, 2011
Century Thrust Joint Venture Agreement | Century Concession in Laos
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