Australian mining giant Rio Tinto has unveiled a rare 2.83-carat violet diamond found in remote Western Australia (WA), which could be worth up to 3 million US dollars.

The oval-shaped rock, the largest of its kind ever discovered at Rio Tinto's Argyle mine operation, was found in August last year and will become the big-ticket item for the company's 2016 Argyle Pink Diamonds tender commencing next month.

It took more than 80 hours to polish the WA gem down to its final form. Originally, the diamond was 9.17 carats and was said to resemble a meteorite.

The company would not put an estimated price on the extraordinary diamond. However, violet diamonds have attracted offers of 750,000 U.S. dollars to 1.5 million U.S. dollars per carat in the past.

Violet-colored diamonds are extremely rare compared to the pink variety.

Over the past 32 years, only 12 carats of quality Argyle violet diamonds have been put up for sale.

The 2.83-carat find is almost three times heavier than Argyle's previous biggest violet stone found in 2008, which weighed about onecarat.

"This stunning violet diamond will capture the imagination of the world's leading collectors and connoisseurs," Argyle Pink Diamonds manager Josephine Johnson told News Corp on Wednesday.

Back in 2008, Johnson described Rio's previous violet gem record holder as a "complete fluke of nature".

The remote WA mine, owned and operated by the second largest mining company in the world, unearths around 90 percent of the globe's pink diamonds, which are more common.

Rio Tinto's 2016 Argyle Pink Diamonds tender will tour Copenhagen, Hong Kong and New York in June, offering private trade viewings for deep-pocketed diamond collectors.