A rare colorless diamond found in the South African is set to be auctioned off in Hong Kong in late May.

The 101.27-carat gem, which was unveiled on Tuesday, is the largest colorless diamond to appear at auction in twenty years and will reportedly fetch no less than $6 million.

Francois Curiel, chairman of jewelery at Christie's said the May 28 diamond auction is unprecedented in Asia. He said only three colorless diamonds of over 100 carats were ever auctioned and each one was sold in Geneva, Switzerland.

In 1990, the Mouawad Splendor, a 101.84-carat pear-shaped diamond, was sold for an astronomical $12.7 million dollars during auction.

The still unnamed stone came from the Premier diamond mine of South Africa, and forms part Christie's Spring Masterpieces Exhibition - a collection which showcases art, jewelery, and contemporary and impressionist paintings worth $342 million.

The collection is open for public viewing until February 27th.