One of the world's rarest diamonds, about the size of an egg or a large lollipop, is going up for auction next month and is expected to fetch $12 million to $30 million.

Sotheby's said that the 102.39-carat diamond, a flawless white sparkler, was the second-largest oval diamond of its kind to be offered at auction. 

The largest, a 118.28-carat diamond, set a record $30.8 million price when it was sold under the hammer in 2013. Two more photos below...