Time and again, a certain 50 ct. D-color potentially flawless mega-rock keeps coming back to Laurence Graff.

The London diamond magnate purchased the top lot at Christie’s New York Dec. 10 Magnificent Jewels auction—a ring that he originally designed, featuring a 50.01 ct. rectangular-cut D-color potentially flawless diamond. He paid $8.37 million, or $167,400 per carat, said the auction house.

Christie’s sold the same diamond to Graff for $4.2 million in 2005, meaning in the intervening years its price has nearly doubled.

“This is the third time that I have owned this beautiful diamond and I am as thrilled today as I was the first time,” said Graff in a statement. “This is one of the finest D-color diamonds in the world and I am delighted to have it back again.”

The sale also set two notable records:

• An ultra-rare 3.15 ct. reddish orange stone—the largest such stone ever graded at the Gemological Institute of America—sold for $2.09 million, setting a new world auction record for a reddish-orange diamond, and a new per-carat record of $666,200.

• An 8.91 ct. sapphire sold for $1.37 million, or $154,000 per carat, setting a new per-carat record for a Kashmir sapphire at auction.

All in all, the sale realized a total of $32.5 million, with sell-through rates of 84 percent by lot and 86 percent by value.

JCK