Mining giant Rio Tinto has unearthed a rare purple diamond from its mine in Western Australia. Weighing 2.83 carats, this diamond is the largest purple diamond ever mined by Rio Tinto, and its auction price could reach as much as US$4 million (approximately 26 million).

According to reports, this oval-shaped purple diamond was mined from the Argyle diamond mine in Australia and has been named “ Argyle purple diamond It will be the highlight of the 2016 annual auction of pink diamonds. The diamond is expected to fetch between US$1 million and US$2 million per carat.

Rio Tinto Group stated that, Purple diamonds are extremely rare. The last time a sizable purple diamond was mined from the Argyle mine was in 2008.

According to reports, more than 90 percent of the world’s rare pink diamonds come from the Argyle mine, which is also the sole source of purple diamonds. The rough “Argyle Purple Diamond” weighs 9.17 carats. It took the artisan more than 80 hours to cut and polish it into its current shape.