A 56.15-carat D color, Internally Flawless heart-shaped diamond described as "perfectly symmetric" is the star lot in Christie's upcoming Geneva Magnificent Jewels sale.

Jewelry News notes that only a few perfect heart-shaped diamonds have been offered for sale at auction in the past two decades. The stone, which the head of Christie's Jewellery Department Jean-Marc Lunel called "the ultimate acquisition for a true connoisseur," is estimated to sell for $9-$12 million.

Other major items among the 320 lots to be auctioned off in the May 18 sale include a ring set with a 6.6-carat rectangular cut diamond with a color grade of Fancy Intense Blue and a clarity grade of Internally Flawless, estimated to sell for at least $4.45 million; a pair of Harry Winston diamond drop earrings set with stones weighing 14.85 and 14.59 carats, which are estimated to fetch over $3 million; and a 21.09-carat diamond ring and diamond necklace, which carry a combined pre-sale estimate of $5.7 million.

Lovers of colored gemstones will also find lots to their liking, as the Christie's sale is also slated to include an historic pair of rectangular-cut emeralds weighing 17.97 and 15.99 carats that once belonged to the Empress Eugenie.