Christie's white diamond could fetch $30 million

STORY: 'The Rock' is the largest white diamond ever auctioned

It is expected to sell for up to $30 million

when it goes under the hammer in Geneva on May 11

The 228.31 carat pear-shaped stone is roughly the size of a golf ball

Christie's is also selling a 205.07 carat yellow stone

named 'The Red Cross Diamond'

(SOUNDBITE) (English) HEAD OF CHRISTIE'S JEWELLERY DEPARTMENT IN GENEVA, MAX FAWCETT, SAYING: “So, it really is a historic moment. I mean, it’s a historic moment for Christie’s having two 200-carat diamonds that we’ll be selling, but the 'Red Cross' to be selling it again 104 years later and obviously, a large proportion going to such an important cause in today’s world is something that, we will probably never see again and something that I’m just so, so excited about.”