Another large diamond has been found at the Letseng mine in Lesotho, a small kingdom in South Africa.

The stone weighs 478 carats and is the 20th largest rough diamond ever found and it may become the largest ever polished round diamond.

Another similar sized rough stone from the same mine was recently valued at $12million. But the clarity and round shape of the new gem mean it could be worth considerably more and in its polished state could sell for tens of millions of dollars.

The Lesotho Promise diamond which was bought by diamond dealer Laurence Graff in 2006 has been cut into 26 smaller diamonds varying in size from .52 carats to 76.41 carats each with a D Flawless grade.

The 603-carat stone yielded 223.35 carats

Graff bought the rough stone for $12.36 million and is expecting quite a haul on his investment, he’s looking for a $50 million payday.