While many of her peers are well into their retirement, the jeweler Elizabeth Gage, 85, still comes to her office in the Belgravia neighborhood of London five days a week. She began making jewelry 60 years ago and while she no longer works at the jeweler’s bench herself, she still designs every piece that bears her name.

Her distinctive designs in yellow gold — which marry bold but balanced proportions with ancient goldsmithing techniques and historical inspiration — more often than not start with a gemstone. Drawing from a vibrant palette of brightly colored tourmalines, including rubellites; tanzanites; and mandarin garnets, which reflect her love of gardens, she specializes in statement rings and brooches, which provide the perfect canvas for her exuberant imagination.

“Color is what I’m after, always,” Ms. Gage explained, looking back on her 60-year career during a recent interview in her elegant sales showroom at a Georgian townhouse, the walls of which are covered in paintings by her mother and grandmother.

Ms. Gage’s decades-long career means that she is one of Britain’s longest-working jewelers. In 2017, Queen Elizabeth II named her as an M.B.E. (Member of the Order of the British Empire) for her services to business, and several of her pieces sit in the permanent collection of the Victoria and Albert Museum, of which Gage has long been a patron, endowing a jewelry curatorship.

“While her outstanding body of work still continues to grow, she has also shown her extraordinary commitment to the field through her generous endowment,” Clare Phillips, the V&A’s Elizabeth Gage curator of jewelry, wrote in an email.

Prices at her shop and online start from £750, or $936, for a gold chain and rise to £71,000 for a cultured pearl, tourmaline and diamond Maharajah pin, resembling something that could have been pinned to the gown of a Renaissance princess.

“History was always very important to me, it still is,” she said, pointing to her Agincourt ring, the first gold jewel she ever made and which she still wears. The ring, named for the decisive English victory over the French in 1415, has been a staple of her collection for six decades and is an intricate weaving of gold, amethyst and peridot-set panels linked top and bottom by tiny, hand-woven chains to ensure maximum flexibility.

“I wanted it to look like a modern drum but by the time I had finished, it resembled a Persian carpet,” she laughed. “I also wanted to make it in red and white, but I didn’t have the money for rubies and diamonds at the time.” Just a few years later, in 1972, it was an Agincourt ring that won her the Diamonds International Award, a now-defunct annual honor that had been sponsored by De Beers.

Ms. Gage was born into an upper-class family in London in 1937, to a British banker father and an American mother. A bout of tuberculosis as a child during World War II threatened her life so she was sent to the United States for treatment and while on bed rest began making clothes and houses for her dolls. Back in Britain for boarding school, she made her society entry as a debutante in 1955 but rejected the prospect of finishing school, instead joining the Chelsea College of Arts a year later. “I just didn’t care what anyone thought,” she said. “I did what I wanted to do.”

It was after Chelsea that her interests switched from fine art to jewelry design. In 1963, she was at the British Museum conducting research for a possible book about the Count of Saint Germain, an 18th-century adventurer, when, fed up with her studies, she slammed a reference book shut and went for a walk. “I came upstairs and the sun was coming in here, and there was a big square table there full of hundreds of beautiful Roman rings,” she said. “I just adored every single one of them and I thought ‘That’s what I want to do.’”

She began designing jewelry and enrolled at the Sir John Cass School of Art (now the London Metropolitan University) where she spent eight years learning goldsmithing, and by 1968 she received her first major commission, from Cartier New York. It was a period of fervent creativity in British jewelry when contemporaries such as John Donald and Andrew Grima were making names for themselves with designs that broke from tradition. As one of the few women on the scene, it took a particular kind of determination to become a jeweler in the first place, let alone one who established a successful business, she said.

While she was at Cass, her mother had bought her a gold ingot but from that point on, she said, she was entirely self-financed, needing to sell any jewelry she made to be able to afford to make more pieces. “I wasn’t sad about that,” she said, “I was just glad because it was the beginning, and you’re always happy in the beginning.”

Another of her signature designs is the Templar ring, which pays tribute to the Knights Templar, a religious military order associated with the Crusades. The style is inspired by Medieval pageantry: In a recent example, made to celebrate her 60th anniversary as a jeweler, a large aquamarine cabochon is set in a shield motif of gold, which in turn sits on a wide band decorated with narrow stripes of blue enamel. The ring features Ms. Gage’s signature border that sandwiches twisted gold wire between two rows of straight gold wire.

Another recent ring design pays homage to her collection for Cartier using a large yellow beryl set in a domed design of red-orange enamel and blue sapphire cabochons.

Her largest market, she said, is the U.S., followed by Britain, where her pieces are made. “As much as I love America,” she said, “the people I work with in London understand what I want, and that makes all the difference.”

Her designs are produced by Ms. Gage’s in-house goldsmiths and an extended network of enamelers, setters and other specialist craftspeople, many of whom have worked for her for decades. “I couldn’t do this without a single one of them,” she said.

Lisa Garoon, 69, a retired lawyer in suburban Chicago, has been collecting Ms. Gage’s work for 35 years. “Elizabeth has such a unique creative voice, you know immediately it’s a piece of her jewelry,” she said by phone. She bought her first Gage piece, a rectangular pin featuring Druzy quartz stones and gold, after graduating from law school in the early 1980s.

“There weren’t many women in law at that time,” she said. “Back then, you wore a suit with hose and heels if you were a woman lawyer, and I thought, I’m going to buy a pin, and it’s going to make me feel powerful, and it did.”

In recent years, Ms. Gage said, she has been lucky enough to attract an entirely new audience in the form of the clients at Dover Street Market, where she is stocked at its London, New York and Los Angeles branches.

“I’ve been a huge fan of Elizabeth for many years, ever since I discovered her pieces in my grandmother’s jewelry box,” Mimi Hoppen, global director of jewelry and watches at D.S.M., wrote in an email. “What I love is how unique and instantly recognizable her designs are. I really respect the fact that she doesn’t care for trends or fashion — she follows her own path and creates what she loves.”