One of the largest white diamonds ever produced by the Argyle mine in the east Kimberley region of WA may be one of the final significant finds of Australia's most famous diamond mine.

Key points: The Argyle diamond mine is scheduled to close down in 2020

The Argyle diamond mine is scheduled to close down in 2020 But that hasn't stop it producing one of its biggest diamonds ever

But that hasn't stop it producing one of its biggest diamonds ever The 28.84 carat stone will now be sent to Belgium where it would be sold

The octahedral-shaped 28.84-carat stone, named Argyle Octavia, was discovered in March.

"We don't see many this shape, or colour, or that clarity, generally out of the mine," Argyle general manager of operations Andrew Wilson said.

"We've probably seen 20 of those in the last 36 years of operations, of the plus-20-carat size."

The diamond dwarfs most others found at the mine. ( ABC News: Evan Morgan Grahame )

Mr Wilson said it was rare for a stone this size to even survive the mining process intact.

"To find one that gets all the way through our crushers, and all the way through the sorting process, out to where we retrieve it … it's quite unusual for it to be able to come out a fully formed diamond," he said.

The last hurrah for Argyle

Diamonds may be forever, but diamond mines are not, and with the Argyle mine due to shut down in 2020, this could be the last major diamond it produces.

"There's a real buzz; there's a lot of people on site who work really hard to be able to find these diamonds, and to have discovered this one is a real thrill for everyone," Mr Wilson said.

The Argyle diamond mine in the far north of WA is set to shut in 2020. ( Supplied: Rio Tinto )

A tender process will now begin, with the stone to be whisked away to the world's diamond trade capital of Antwerp in Belgium.

The company was unwilling to attach a value to the stone ahead of the tender process.

"It will go to Antwerp, and through our auction process, and the market will determine its value," Mr Wilson said, adding that the diamond would be sold as a rough stone.

"Let's hope there's somebody who's got a passion for West Australian Argyle diamonds … hopefully we have that opportunity to see it on a beautiful piece of jewellery."