Grenville Thomas left the Old World as a young mining engineer to become a pioneering prospector and company-builder in the New World, where he made a series of important mineral discoveries and contributed to the advancement of Canada’s fledgling diamond industry. He began his career as a 16-year-old coal miner in his native Wales, moving to Canada after graduating from University College, Cardiff, in 1964. He found his calling in remote northern Canada.  Inspired by its vast untapped mineral potential, he rose to the challenge of working in unforgiving terrain under extreme conditions. He honed his prospecting skills and over several decades built up a multifaceted track record of discovery, culminating with the early 1990s discovery of diamond deposits ultimately developed into the world-class Diavik mine in the Northwest Territories (NWT).

Gren Thomas began his Canadian career with Falconbridge, taking posts in the Sudbury nickel camp of Ontario, and at the Giant gold mine in Yellowknife, NWT. He left Giant to form his own company specializing in NWT mineral projects, a decision reflecting his entrepreneurial nature and affinity for the junior sector, and spent time looking for nickel on the Arctic coast near Perry River. In 1975 he founded Highwood Resources to explore in the North, which led to the discovery of the Thor Lake rare metals deposit, now under development by Avalon Ventures.

In 1980, he formed his flagship junior company, Aber Resources, which subsequently discovered the Sunrise Lake massive sulphide deposits. In late 1991, Aber moved quickly to stake a large group of claims in the Lac de Gras region based on reports of a diamond discovery. The decision to stake surrounding ground at the onset of winter was a bold one, as Aber was cash-poor and the diamond discovery was widely considered to be a geological curiosity at the time. Thomas enlisted daughter Eira, a geologist, to help advance exploration efforts. Raising capital was a continual challenge, as was battling the perception that new discoveries were unlikely in the region. But Thomas persevered, attracted global mining giant Rio Tinto as a joint venture partner, and accelerated the race to find the next economic diamond deposit. His vision and perseverance were rewarded when Aber announced the first discovery on the Diavik property in 1992. By 1995, four economic diamond deposits had been discovered and with the support of Rio Tinto, Aber’s Diavik discoveries were developed into one of the world’s richest diamond mines, producing annually more than 10 million carats, worth an estimated $800 million-$900 million. Diavik has also generated jobs and immense benefits for northerners, including aboriginal communities. Aber has now changed its name to Harry Winston Diamond Corporation to reflect its involvement in the luxury goods market. Thomas’s discoveries and leadership role in advancing Canada’s diamond industry have won him many honours, including the PDAC’s Prospector of the Year Award for 1999.  He continues active in northern exploration through his involvement with Strongbow Exploration and North Arrow Minerals.