The D-color, internally flawless diamond leads the Geneva Magnificent Jewels auction.
Sotheby’s created an Instagram filter for the crown, estimated to sell for up to $1.5 million.
The internally flawless Type IIa stone is the star of Christie’s Magnificent Jewels sale next month in Hong Kong.
The largest Kashmir sapphire to hit the block, according to Sotheby’s, and several stones weighing more than 100 carats are on offer.
The sale of items belonging to the queen’s great-great granddaughter garnered three times more than expected.
“Colorful Whimsy: Jewels by Michele della Valle” was full of springtime pastels.
It will be the largest single-owner collection of the German brand’s jewels to appear at auction, Sotheby’s said.
Every lot was sold at the Sotheby’s auction, with 98 percent topping their highest pre-sale estimates.