A bright pink diamond described as one of the cleanest in the world could fetch more than $21 million at an auction in Hong Kong in October.
The 11.15-carat gem has been named the Williamson Pink Star in homage to two other pink diamonds.
One of them is the CTF Pink Star, a 59.6-carat oval diamond that sold for a record $71.2 million in 2017. The other, the 23.6-carat Williamson, was gifted to Queen Elizabeth for one of her earrings. The rare stone was discovered in a mine in Tanzania, where the "Williamson Pink Star" comes from.

“Pink diamonds are extremely rare in nature. Then factors such as being over 10 carats, fineness and type are added, and then the value peaks," explains the head of jewelery at Sotheby's auction house.
High-quality colored stones are bought by the wealthiest strata of society and high bids are expected when the pink diamond hits the auction stand.