At 12.76 carats, the remarkable find is said to be the largest stone ever discovered in the country and is expected to sell for up to $10.6 million, according to the Herald Sun.

Named the Argyle Pink Jubilee, the gem is similar in color to the 24-carat Williamson Pink given to Britain's Queen Elizabeth II as a wedding gift, explains the Telegraph.

"A diamond of this caliber is unprecedented -- it has taken 26 years of Argyle production to unearth this stone, and we may never see one like this again," Argyle Pink Diamonds Manager Josephine Johnson said in a statement.

The gem is being cut and polished into a single stone over a 10 day period and will be up for auction later in the year, Rio Tinto said.

In November 2010, Sotheby's Geneva office sold a 24.78-carat fancy intense pink diamond for more than $46 million, which set the world's auction record for any diamond and jewel at $1.86 million per carat.

More than 90 percent of the world's pink diamonds come from the Argyle mine.