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A Canadian mine says it has broken its own record for the largest diamond ever found in North America.

Dominion Diamond Mines has announced the "unexpected" discovery of a 552-carat yellow gemstone.

It was found in October at the Diavik Diamond Mine in the Northwest Territories, which is 135 miles (215km) south of the Arctic Circle.

The company says this diamond "far surpasses" the previous record-holding stone found at the mine in 2015.

The Foxfire - a two-billion-year-old 187.7-carat diamond unearthed at the Diavik mine - was displayed around the world, including for a couple of months at the Smithsonian's National Museum of Natural History in Washington and for a few weeks at Kensington Palace in London.

Kyle Washington, chairman of Dominion Diamond Mines, which owns 40% of the Diavik mine, said in a statement that this latest find "tops the list" of beautiful diamonds.

"The colour and texture of the diamond are a unique example of the journey that natural diamonds take from their formation until we unearth them," he said.

The stone measures 33.74mm by 54.56mm (1.3 inches by 2.14 inches).

The gemstone will not be sold in its current rough form but will instead be cut and polished in the coming weeks.

"The size and highly technical nature of this stone means that only a handful of master cutters in the world are qualified to polish it, ensuring that the stone's beauty, colour and brilliance are maximised," the company said.

It says it is too early to estimate the value of the stone but noted that the Foxfire, which was eventually cut into two pear-shaped earrings, was recently auctioned for $1.5m (£1.2m).