A New York auction house has put on display what it says is the world's greatest white diamond: a 118-carat stone from Africa the size of a small egg - which will be put up for auction next month.

The diamond, which is about the size of a small egg, could be seen yesterday at Sotheby's Manhattan headquarters. The oval shaped stone was mined and cut two years ago in South Africa. It will be auctioned in Hong Kong on Oct. 7 and has been estimated to be worth $28 million to $35 million.

In terms of size, quality, polish and color, it's described as "the greatest white diamond ever" by international diamond experts. The stone was discovered in 2011 as a 299-carat rough diamond.

The current record for any white diamond is $26.7 million. That stone, which was sold in Switzerland last spring, was over 100 carats.