The biggest diamond ever found in North America has been unearthed by Dominion Diamond Mines and Rio Tinto Group at a mine in Canada’s frozen north. The 552 ct yellow gem was found at the Diavik mine in the Northwest Territories, and is almost three times the size of the next largest stone ever found in Canada. While Diavik and the neighboring Ekati mine produce some very high quality diamonds, they’re not renowned for the sort of huge gems normally found in southern African mines.