New York’s glitterati got their first peek at the De Beers store last night. But the De Beers party to be at was on Tuesday night, when the diamond company’s chief executive, Guy Leymarie, invited an A-list crowd to sparkle and mingle in a vast, unoccupied condominium at the Time Warner Center.

In the absence of glass cases and other jewelry displays, it was up to the women to show how beautiful a diamond can be.

Of course, the right setting is everything, and for that, De Beers turned to the 80-carat designer David Monn.

Those who had the good fortune of seeing Mr. Monn’s past work – at benefits for the Costume Institute, the New York Public Library, and the New York City Ballet, for instance – immediately recognized a few of his signatures: gigantic bunches of gardenias, round green topiaries, and sparingly placed white candles.

Mr. Monn offered much more on this occasion. The city’s museums and theater halls are dramatic spaces, but they also restrict what a decorator can do. Here on the 79th floor of one of the city’s most expensive residential buildings, Mr. Monn started with a blank canvas.

He played with that idea, creating dramatic all-white and all-black rooms that became showcases for the two elements that assure a good party in New York: art and fashion.

In the white rooms, there were plump white couches and even a fluffy white fur area rug. The furniture, too, was white. That made the Renaissance paintings hanging on the walls all the more dramatic.

In the black room, guests lounged on black leather couches, softened by gray-black fur throws. Here it was a large-scale contemporary painting of geometric color blocks in turquoise, peach, and yellow that warmed the room.

Don’t think Mr. Monn is as precious as the diamonds he was helping to celebrate. Not every piece of furniture fit the scheme. Some of the chairs in the white room were a warm brown, their backs in the shape of a crocodile.

A decorator can control many things about a party, but what hundreds of guests choose to wear is decidedly not one of them. On this night, many guests showed up in black and white, perfectly synchronizing with the decor and making Mr. Monn a very happy designer indeed.

Guests included Muffie Potter Aston, Susan Fales Hill, Lauren Pack, Susan Shin, Ann Tenenbaum, Somers White, and Bettina Zilkha.