The largest flawless vivid blue diamond in the world is expected reach a price of bewteen $21-25 million when it is sold at auction next month.
Known as 'The Blue' the stone has been put on display in New York ahead of its sale next month in Geneva.
Head of Jewelry at Christie's Rahul Kadakai said:
"Thirteen-carat vivid blue being the strongest saturation in a blue diamond, deeply saturated rich blue color and flawless. So the stone is internally and externally bereft of any imperfections.
"So this is the largest flawless vivid blue diamond in the world. So in simple terms, it's the best blue diamond in the world."
Very little in known about the age of the stone, or where it was mined.
'The Ocean Dream' diamond will also be going under the hammer in the sale. It is a five and a half carat blue-green diamond which could make between $7.5 to $10 million dollars.