Queen Camilla Debuts Queen Elizabeth's Aquamarine Tiara at Palace Party

The Queen officially has a new headtopper in her royal rotation

Queen Camilla is shining one of Queen Elizabeth's tiaras, a brand new addition to her royal rotation.

On Nov. 20, the Queen, 77, joined King Charles and Prince William for the Diplomatic Corps Reception at Buckingham Palace. While Kate Middleton is usually a mainstay at such diplomatic events, she hasn't fully resumed royal duties since announcing on Sept. 9 that she has completed chemotherapy treatment for cancer.

Queen Camilla shimmered in what's informally known as the Aquamarine Ribbon Tiara, making her debut in the headpiece. The Aquamarine Ribbon Tiara features five emerald-cut aquamarine gems, connected by a ribbon-like setting of diamonds.

According to The Court Jeweller, Queen Elizabeth wore it just once in public, slipping it on for dinner during a royal tour of Canada in 1970. Its provenance is a bit of a mystery, and the sparkler has been rarely seen since.

Related: Prince William Steps Out for Glam Buckingham Palace Reception as Kate Middleton Skips Event

Sophie, the Duchess of Edinburgh is known to reach for aquamarines, and previously wore the Aquamarine Ribbon Tiara to two international royal wedding celebrations. Prince Edward's wife glittered in the headpiece for a pre-wedding dinner before Hereditary Grand Duke Guillaume of Luxembourg in 2012 and wore it again for the royal wedding of Princess Madeleine of Sweden in 2013.

The tiara hadn't been seen until Queen Camilla took it out of the royal vault for the latest Diplomatic Reception, where she paired it with a midnight blue velvet dress by Fiona Clare. She completed the look with her own aquamarine and diamond necklace and earrings, plus the King's Family Order.

While Princess Kate seems to favor demure headtoppers, Queen Camilla doesn't shy from going big and bold. She has worn the Greville Tiara, distinct for its honeycomb design and large size, many times since marrying King Charles in 2005, and had a few tiara debuts from the late Queen Elizabeth's collection since her husband's accession in September 2022.

In November 2023, Queen Camilla and Princess Kate, 42, both had tiara firsts at the state banquet at Buckingham Palace celebrating the incoming state visit from South Korea. The Queen wore in the Burmese Ruby tiara, the rubies perhaps a flag dressing tribute to South Korea's national flag, while the Princess of Wales surprised in the Strathmore Rose Tiara.

Related: Queen Camilla's Most Glittering Tiara Moments — See Her Go-To Sparkler!

The delicate piece originally belonged to Queen Elizabeth, the Queen Mother and had not been seen for nearly a century before Kate wore it.

King Charles was known to be exceptionally close with his grandmother, who died in 2002 at age 101, and some interpreted Princess Kate's wearing it as a nod to her close bond with Charles.

"I think it’s lovely as the King was so close to the Queen Mother and knowing that one of her most precious pieces of jewelry is being worn by his daughter-in-law gives a really emotional tie between the generations," Bethan Holt, the author of the book The Queen: 70 Years of Majestic Style, told PEOPLE at the time.

"It has been said that Kate has looked for inspiration to the Queen Mother in terms of how she conducted herself and so to have that tiara symbolizing that, in such a public moment, I think it is really significant," she added.

2024 looked different for both King Charles, 76, and Princess Kate, as both royals announced earlier this year that they were undergoing treatment for cancer. Buckingham Palace shared in February that the King was  diagnosed with cancer and began treatment, while the Princess of Wales shared in March that she was undergoing treatment for cancer.

The King's treatment is thought to be ongoing, and Princess Kate shared in September that she completed chemotherapy.

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In a remarkably personal interview as his 2024 Earthshot Prize Awards drew to a close in South Africa earlier this month, Prince William, 42, called 2024 "the hardest year in my life.”

"It's been dreadful. It's probably been the hardest year in my life," the heir to the throne said in part. "But I'm so proud of my wife, I'm proud of my father, for handling the things that they have done. But from a personal family point of view, it's been, yeah, it's been brutal."