Rio Tinto says it has attracted strong interest from Asian and European buyers at its annual pink diamond sale.

Successful bidders for the Argyle Pink Diamonds Tender were from both established and emerging markets, with buyers snapping up 56 single pink diamonds, two red diamonds and 19 blue diamonds.

Argyle Pink Diamonds manager Josephine Johnson said the precious gem collection was keenly contested before tenders closed on October 15.

"We were delighted to see such a strong appetite for this unique rainbow collection," Ms Johnson said

"Several beautiful diamonds from the collection have a new home in India, an important emerging market for rare pink diamonds."

The "hero blue diamond," Argyle Elektra, is headed to Japan, the most established market for pink diamonds.

Rio Tinto said many of the successful bidders were part of the exhibition at Kensington Palace on October 9th.

John Glajz was the successful bidder of the most valuable diamond from the collection, Argyle Siren, a 1.32 carat pink diamond.

"I look forward to designing an heirloom piece of jewellery to honour its heritage," he said.

The Argyle Diamond Mine in the Kimberley WA produces more than 90 per cent of the world's rare pink diamonds.

But Rio Tinto's diamond business has struggled in recent times.

Rio earlier this year announced it had begun a strategic review of its diamond business, which involved exploring options such as divesting the mines.

At the time, the diamonds and minerals business's chief executive, Harry Keynon-Slaney, hinted at the fact that the assets were too small, saying Rio's strategy was to operate large, long-life, expandable assets.