SOMBA K'E/YELLOWKNIFE - De Beers Canada and joint venture partner Mountain Province Diamonds have found the single largest diamond ever recovered from a core sample in Canadian exploration history at their Gahcho Kue project northeast of Yellowknife.

The 25.13 carat diamond, weighing just over five grams and valued at $440,000 US, was unearthed from the site during a bulk sample program early this year and discovered two weeks ago at a processing laboratory in Johannesburg, South Africa.

"We've recovered some pretty large diamonds from Gahcho Kue over the last few years. The next largest one is a 9.9 carat. But when De Beers advised us that a 25 carat gem quality diamond had been recovered, we were blown away," said Patrick Evans, chief executive officer for Mountain Province, which retains a 49 per cent interest in the project.

De Beers has a 51 per cent stake, with an option to raise that number to 60 if it helps fund the development of the mine. As of press time, a spokesperson at De Beers could not be reached for comment.

Making the discovery of the diamond more remarkable is the fact that the stone made it through De Beers' crushing facility in Grande Prairie, Alta., which reduces ore to 12 mm before air-freighting it to Johannesburg, without being compromised.

"It's a miracle that it got through," said Evans. "This diamond, on its long axis, is almost 20 mm, and on its short axis, 15 mm.

"It must have been a particularly hard piece of granite or something that went through with it. Otherwise, the diamond would have been crushed."

While it will not result in an earth-shattering reassessment of Gahcho Kue, the stone does confirm the potential of the project, said Evans.

"It gives us the confidence to assume that there will be a population of large diamonds coming from the future Gahcho Kue mine," he said.

Evans acknowledged an industry rumour that Mountain Promise and De Beers are mulling the sale of the property.

"We've come to a natural point in the development of Gahcho Kue where the partners are considering all options," he said.

The future mine, which has an expected life of approximately 15 years and will employ 400 people during production, is still on track to become operational by 2012, he added.

Mike Vaydik, general manager of the NWT and Nunavut Chamber of Mines, was not surprised by the discovery.

"We knew there were big diamonds in there before," said Vaydik. "I don't think this would be significant enough to cause a major shift in plans."

The previous record-holder for a drill core sample stone was Tahera Diamond Corp., which recovered a 23.8 carat diamond from its Jericho Diamond mine in Nunavut eight years ago.

Operations have ceased at the Jericho mine while a buyer is sought by the company, which has been under creditor protection since January.