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The Queen’s magnificent jewelry collection includes several pieces so incredibly rare that they manage to stand out among the rest of the spectacular glitter. Today’s piece, the Williamson Pink Diamond Brooch, includes one of the rarest flawless pink diamonds in the world!

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The pink diamond set at the center of the brooch was discovered at the Williamson mine in Tanzania in 1947. The owner of the mine, Canadian geologist John Thoburn Williamson, decided to present the uncut diamond to Princess Elizabeth as a wedding gift that November. The rough gem, which weighed in at 54.5 carats, was displayed at St. James’s Palace ahead of the royal wedding. Williamson, reportedly keen to avoid the grand social situation that would accompany a personal presentation of the gift, had it presented by a representative instead.

In 1948, the princess turned to diamond cutters Briefel and Lemer, headquartered in Clerkenwell, to transform the rough diamond into a faceted gem. That March, Elizabeth visited the firm to check in on the cutting process. The Montreal Gazette reported that she “smiled delightedly” when she saw the progress that had been made on the diamond. She was accompanied by her jewelry-loving grandmother, Queen Mary; the paper wrote that “true to form,” Mary “asked numerous questions of a technical nature” during the hour-long visit. A few weeks later, after the cutting process was finished, the new 23.6-carat diamond was displayed as part of a major diamond exhibition in London. Other pieces from Elizabeth’s jewelry box, including the Flame Lily Brooch and the South African Diamonds, were also exhibited alongside the Williamson Pink that May.

With the diamond now ready to be mounted in a piece of jewelry, Princess Elizabeth looked to her parents’ favorite jewelry firm, Cartier, to create a suitable setting. Newspapers reported in October 1949 that she was having trouble deciding precisely how the diamond should be used: “At first the Princess thought it might be fitted into her personal crown, but experts considered it might lose its glory among so many other jewels.” Some suggested it would look best as a pendant on a necklace. Ultimately, though, the stone was placed at the center of a jonquil brooch designed by Frederick A. Mew of Cartier’s London branch. (At the same time, Mew was at work on the changes to the Greville Tiara ordered by the Queen Mother.) An additional 203 white diamonds — mostly brilliants, but also baguettes and marquises — were used to finish the jewel. The brooch, made of platinum, was completed in 1953, the year that Princess Elizabeth was crowned as Queen Elizabeth II.

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The piece became a favorite item in the new Queen’s jewelry box almost immediately. The brooch was front and center in a series of portraits, also featuring Prince Charles and Princess Anne, that were taken by Marcus Adams in late 1954.

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The size of the brooch, and the prominence of the famous pink diamond, made the piece especially well-suited for important diplomatic occasions. The Queen has worn the brooch often for state visits, including a welcome ceremony for President Francisco Craveiro Lopes of Portugal in October 1955.

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In May 1957, she wore the brooch as she sailed into Copenhagen’s harbor aboard Britannia for the start of a state visit with King Frederik IX and Queen Ingrid of Denmark.

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Three years later, in July 1960, the Queen chose the brooch again for a welcome ceremony during the state visit of King Bhumibol Adulyadej of Thailand and his wife, Queen Sirikit.

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The classic design of the piece has made it a diplomatic mainstay throughout the Queen’s reign. Here, in December 1992, she wears it aboard the Britannia, where she and the Duke of Edinburgh hosted a dinner for European heads of state (including French President Francois Mitterand, shown with the Queen above) during a European Council summit. On this rare evening outing for the brooch, she paired it with the dramatic Greville Chandelier Earrings.

The Queen has often selected the brooch for important personal occasions as well. She has twice worn it for her annual Christmas broadcast, with appearances in 1968 (shown above) and 1998.

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She has also worn the brooch twice for weddings of her children. In 1981, she wore the brooch for the wedding of her eldest son, the Prince of Wales, and Lady Diana Spencer.

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And in 1999, she chose the brooch for the wedding of her youngest son, the Earl of Wessex, and Sophie Rhys-Jones.

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The natural flower design of the brooch also makes it appropriate for one of the Queen’s favorite pastimes: days at the races. Above, she wears the brooch with four strands of pearls for the Epsom Derby in June 1957.

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The piece has also made appearances at Royal Ascot, including this outing in June 2011.

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One of the highest-profile outings for the brooch in recent memory came in June 2014, when she wore it at the Elysee Palace during an official visit to Paris. The brooch has also been loaned out for prominent exhibitions in recent years, including the landmark Cartier exhibition held in Canberra in 2018.