Object Lesson

Rock shop

For jewel collectors who can't wait for their next bling to go on the block, now there's Sotheby's Diamonds, a retail shop on the sixth floor of the auction house's New York headquarters. A joint venture with the Steinmetz Diamond Group—which cut the 203-carat De Beers Millennium Star—it offers 60 stones in its inaugural collection, like this 58-carat whopper.

Specs A 58.01-carat Asscher-cut diamond that's both internally flawless and absolutely colorless.

Provenance The shop can't reveal the exact mine the stone came from, but we do know it's from southern Africa and was originally 170 carats.

Not for You? Sotheby's Diamonds bespoke service will track down any diamond that is not already in its inventory, then custom-make a setting for it.

Details $5.5 million. At 1334 York Ave., New York; 212-894-1400; sothebysdiamonds.com.