Sissy Yates approaches her work as a jewelry designer like it’s a treasure hunt, scouring the world for what she calls “beautiful, shiny, colorful gems.” When she unearths a stone she loves, Yates says she has an almost visceral reaction. “Something about it makes me so happy.”

Yates has always felt this way about stones, which as a child she collected from the woods surrounding her Washington home and then polished in a rock tumbler. While it seems an unlikely hobby for Yates, who grew up among the District’s glitterati as the daughter of White House Social Secretary Mabel “Muffie” Cabot (née Hobart) and Washington Post reporter Eric Wentworth, Yates says her enthusiasm could not be tempered. “We moved a lot, and my rock collection always became a point of contention,” she recalls. “It was heavy, and my mother would try to insist that the rocks were not moving with us.”

But the rocks always followed, and by her teenage years Yates was using them to make jewelry for her friends and family. But as adulthood dawned, her penchant took a backseat to college, careers in Los Angeles and New York (where she worked at The Metropolitan Museum of Art), and later on, her responsibilities as a mother of three.

It was only at the encouragement of her sister, actress and author Ali Wentworth, that Yates finally agreed to take her longtime hobby to the next level. In 2007 she debuted 50 of her necklaces in a show her sister hosted at her DC home. The entire collection sold in two hours. “It was at that moment that everything changed,” Yates says. “The lightbulb went off, and I realized that what I really wanted to do was staring me right in the face.”

That year she officially launched Sissy Yates Designs, a collection of fine gemstone jewelry—pieces include stones such as opal, topaz, coral, and lapis—at affordable prices. Since then she has grown a devoted following of style-setting celebrity customers, including Mariska Hargitay, Debra Messing, and Good Morning America’s Lara Spencer.

Yates eschews trendy looks in favor of universal, timeless pieces, but she admits her style is constantly evolving, inspired by everything from Old Hollywood and museum collections to her capital hometown. “This city is about power, but it’s also about being under the radar when it comes to style,” she says. “Women here want to be classy and chic, but discreet.”

While Yates says she is still as excited about a bright and shining gem as she was as a child, she derives the most pleasure from the moment a client tries on one of her pieces and looks in the mirror. “I love seeing a woman light up,” she says. “In that moment, I see that style doesn’t have to be complicated; you can wear something as simple as a T-shirt, but put on a beautiful necklace and be totally transformed.”