David Yurman knows most things about jewelry, but at the moment he is especially keen on pearls. That pearls are breathing, organic beings is a fact he relishes. He knows that while most pearls are round, others turn up dramatic Paisley shapes and funny funnel-cake shapes and can have offbeat colors like blue and green. At each of these things, he marvels. He also knows, but is less moved by, facts like when you place a black pearl next to a white one, the black must be 10% to 15% larger, because otherwise, side by side with the white, it will appear smaller.

Black, white and untold other varieties of pearls have been displayed in Yurman's signature jewelry, in shops that bear his name and in many that don't, for a total of 200 locations this fall, thanks to his latest obsession. That is why, one afternoon this past summer, he was examining several pearl necklaces on the design floor of his Manhattan office, pieces his head technician, Leslie Ewing, had been tending. "You need a pearl to balance this chain," Yurman said of the first. Leslie held up another, a single-strand cable necklace with a mix of pastel-colored cultured pearls dappled around it. "We'll have to mix in freshwater," Yurman said. "It's kind of—" and he slumped to one side, one arm to the floor. Ewing raised an eyebrow at his proposed pearl indiscretion.

"At the end of the day you have to step back and look at it and say, 'Does this feel right?'" Yurman later explained. "And you just know it. There's no formula per se. It either feels right, or it doesn't. Then there's Sybil—her feeling about it. Sometimes you get too close. You make the soup, and you can't taste it. You have to go to someone and say, 'Is there too much cumin in this thing?'"

Sybil is Yurman's wife, a painter and president of David Yurman Inc. Together they have created a jewelry empire that has just the right amount of cumin: an estimated $450 million in annual sales. Their line is a top seller at Neiman Marcus and is worn by the likes of Gwyneth Paltrow, Barbra Streisand and Mary J. Blige. Women hoard it like chocolate. At dinners in particularly Yurman-happy regions, like Atlanta, Dallas and San Diego, collectors haggle not only over the Moroccan braised lamb but also over who owns the most Yurmans. Sixty is the highest tally recollected to date.

Yurman recently began designing timepieces, even opening a command center in Switzerland. His watches are worn by Steven Spielberg and Kevin Spacey. Wildly successful ad campaigns—featuring models Amber Valletta and Kate Moss and photographed by Peter Lindbergh—solidly place his pieces in the high-fashion category. David Yurman shops have secured spots alongside European-establishment jewelers like Cartier and Van Cleef & Arpels.

Dressed in a lavender shirt and with a shock of white hair, Yurman presides with bonhomie—and with Sybil—over a new 65,000-sq.-ft. headquarters in Manhattan's Tribeca neighborhood. There are two vast floors, hundreds of employees and a commanding entrance manned by strapping doorboys. Yurman jokes with the engineers as they solder ring samples. Nearby, aerospace technology normally used to turn draft drawings into airplane parts here transforms sketches into parts for cocktail rings and chokers. "All of this happened while we were busy making jewelry," Yurman confesses. "We didn't intend for this."

Yurman's early adult years were spent in bohemian romps with some of the most prominent Beat artists of the '60s. Having discovered metal sculpting through his craftsman father—and since Yurman was "not too good at following the organized religion of education," he says—he landed with his sister and her sculptor boyfriend in Provincetown, Mass., where he quickly became part of "a curious mix of writers and artists and wannabe artists," which included Norman Mailer ("He was the ringleader"), painter Franz Kline and poet Gregory Corso. "They would meet at a place called the Fo'cs'le and drink a lot of beers and talk about art, mainly about trying to get away from élitism. Things like 'Craft is an art.' 'Fine art? Art is art.' 'Well, the difference is function.' I thought, Wow, this is great." Then in Big Sur, Calif., he joined the anti-Establishment orbit of author Ken Kesey, working and playing with poet-painter Lawrence Ferlinghetti and sculptor Ron Boise.

Yurman's sculptures nestle here and there throughout the Tribeca space. Made of bronze so textured it looks primitive, they depict graceful and exquisite abstractions of the human form. In one, a pair holds hands, suspended buoyantly in the air—joyful and free and full of life, and romantic and dancing. Like Matisse's dancers. "It is," Yurman says. "Well, it's Sybil and me, but it's based on Matisse." "He is a poet," Sybil says later. "The way he thinks, the things he says, his sculpture. And the jewelry."

Yurman's outlook was deeply influenced by Jacques Lipchitz—the renowned sculptor and colleague of Picasso and Modigliani—under whom Yurman apprenticed. Lipchitz created imposing Cubist human forms out of bronze, until suddenly his sculpture changed course. "It occurred to him it was going nowhere. He was reducing the human spirit to a cube," Yurman recalls. "One day he said, 'I'm going to go back to Expressionism and what expresses the human condition.' He said that ultimately you must find what your point of view is, really define it. That's the most important thing for an artist, to express his feeling and his point of view. So I listened to that."

Having created a procession of protest art—angry displays made of concrete and bullets—Yurman returned to his romantic sculptures, many of them angels. Sybil—whom Yurman had met and fallen in love with when they were working for the same artist—asked him to turn one of the angels into a belt, and that was the beginning of their jewelry.

The first sketch of that first angel clasp was done in pencil on a Ramada Inn notepad. It now sits behind glass among other memorabilia that line the headquarters' walls. Yurman calls the switch to jewelry "entering the mainstream." (He did a stint at Cartier, designing under the Cartier stamp. And when his own designs saw some success, he approached Tiffany about designing under its auspices. "Thank God they said no," he says.) But his poetic vision and Beat recklessness show up in every piece. The signature cable bracelet—twisted silver and gold strands with gemstone tips—made him a phenomenon in the mid-1980s, and while luxurious, it's unintimidating, even familiar. The same design was all the rage in ancient Minoan, Scythian and Egyptian civilizations. "It references history," Yurman explains. "I think we're comfortable with something we kind of know we've seen before. Maybe it was in our collective unconscious."

A mishmash of strands—a chunky silver chain, a loose-link silver chain, a microfine silver chain and a string of small cultured pearls—is tossed together into a hip and harmonious tangle of necklace. "For me, it's a very relaxed form of luxury," Yurman says. "I always go back to saying it's your favorite pair of jeans. Worn jeans have this authenticity about them."

In this season's cocktail rings, a single, brilliant cushion-cut stone—lavender amethyst, blue topaz, champagne citrine—gets a relaxed look with a side doodle: a strip of inlaid diamonds, rubies or multicolored sapphires along the band. And for day to evening, Yurman takes Tahitian black pearls and subtly mixes in diamonds, yellow sapphires and rubies. "The luxury is really in making the material the hero," Yurman explains. "It kind of allows you to feel 'This is my piece,' rather than walking in and expecting to have 50 horns blowing."

Yurman is much more partial to the blues than to blowing horns. His CD player is stacked with Elmore James, Muddy Waters, B.B. King, Ike and Tina Turner. "A group called the Campbell Brothers comes from Rochester and sings gospel," says Yurman. "They're so great, your hair stands up and you jump up and you dance."