The world's top miner, BHP Billiton, said it will spin off several of its lower-performing assets into a new global mining and metals company which will be listed in Australia. Several of the assets which will make up the new company were part of Billiton when BHP acquired the company in 2001. The yet unnamed company, dubbed NewCo, will focus on aluminum, coal, manganese, silver and nickel. BHP said it will continue to focus on iron ore, copper, coal, potash and petroleum. Shares of BHP declined in London trading after the announcement as investors digested the news. The Deal's Paul Whitfield says it could be challenging for BHP shareholders because NewCo will only trade in Australia and some funds are not allowed to hold securities which are not traded on their local exchange. TheStreet's Ruben Ramirez spoke with Whitfield about what the spin off means for BHP.