In a three-year span, Telfer guided Wheaton River from a roughly $10 million company to one with an approximately $2.4 billion valuation. In 2004, Wheaton River Minerals announced plans of merging with IamGold Corp. When IamGold shareholders rejected the merger, it left the door open for a different merger. In 2004, Wheaton River merged with established Goldcorp Inc. in a $2.4-billion share swap that saw Goldcorp absorbing Wheaton River. Following the merger, Goldcorp's Board of Directors appointed Telfer as Goldcorp's new Chief Executive Officer. In 2006, Telfer led in Goldcorp's friendly acquisition of Glamis Gold, a merger that at the time created the world's third largest gold mining company. The new, larger company retained the Goldcorp name. The merger also shifted Telfer from Chief Executive Officer of Goldcorp to the company's Chairman. In April 2005, Wheaton River Minerals faced a hostile bid for its silver assets by Coeur Mining Inc., then called Coeur d’Alene Mines. Rather than accepting the hostile bid, Telfer led in separating off Wheaton River Minerals’ silver assets into a new company to be called Silver Wheaton Corp. Telfer was also instrumental in brainstorming the concept behind Silver Wheaton, which is a mining company that does not do any mining itself, but instead acquires silver byproduct from other mining companies that are focused on other precious metals. In April 2006, Telfer stepped down from his role as director of Silver Wheaton Corp. In addition to his work with Wheaton River Minerals and Goldcorp, Telfer has founded and led other mining companies. In 2006, Telfer and Frank Giustra formed UrAsia Energy, a uranium producer operating a mine in Kazakhstan. Telfer served as UrAsia's Chairman. In 2007, UrAsia merged with Uranium One Inc., with Telfer continuing on as Uranium One's Chairman. Telfer contributed in launching Terrane Minerals, Tahoe Resources, Peak Gold and Primero Mining. Telfer is also the co-founder of Renaissance Oil Corp., an oil company currently developing shale and oil fields in Mexico. Telfer launched Renaissance Oil after Mexico began privatizing its oil and gas industry. Ian Telfer served as Chairman of the World Gold Council (WGC) from 2009 to 2013. Over the years, Ian Telfer has contributed to a number of philanthropic causes. In a 2011 interview, Telfer commented that because personal wealth came to him relatively late in life, it has allowed him to think beyond his own personal gain and place a higher value in philanthropic endeavors.