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Convertible tiaras are often some of the most popular jewels in royal vaults, but it’s been quite a while since we’ve seen the Congo Diamond Necklace Tiara, one of the heirloom wedding tiaras of the grand ducal family of Luxembourg.

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The piece dates to the middle of the twentieth century and was made by Van Cleef and Arpels using Congolese diamonds. In 1953, the necklace/tiara and its matching bracelet were given by the Belgian Congo as a wedding present to Princess Joséphine Charlotte of Belgium, who was marrying Hereditary Grand Duke Jean of Luxembourg.

As a sidenote: the now-Democratic Republic of the Congo and the Belgian royal family have a complicated and often tragic historical relationship. While many colonies were claimed by countries, the Congo was personally owned by Leopold II of the Belgians himself. The history of the lucrative ivory and rubber trades and the atrocities that occurred as a result have had long-lasting consequences, to say the very least.

The Belgian Congo gained its independence seven years after Joséphine Charlotte’s wedding. Although the pieces were a gift from a then-colony, they are not, as is often stated, set with “blood diamonds.” Blood diamonds (or “conflict diamonds”), by definition, are gems mined in a war zone and sold on the black market to finance insurgencies. Although the DRC has had issues with conflict mining in more recent decades, the gems in this suite of jewelry are not conflict diamonds. They have a colonial history, which brings along many other issues, but blood diamonds they’re not.

Joséphine Charlotte began a family tradition when she wore the diamond sparkler as a tiara during her religious wedding ceremony. (She changed into the Belgian Scroll Tiara for portraits afterward.) The marriage ceremony itself, however, wasn’t precisely the most joyful of weddings. The bride struggled through the ceremony, appearing shaken and confused, leading the groom to inquire after her health multiple times at the altar. The press had a field day with Joséphine Charlotte’s tears, murmuring that she was upset because the relationship had been a political arrangement. The official excuse was that she was ill; one diplomat’s wife even claimed that the bride’s new contact lenses had caused her to cry during the wedding.

Whatever the true cause, Joséphine Charlotte was stressed enough that the couple’s honeymoon was postponed. She and Jean were eventually able to embark on their trip to Africa, and their marriage lasted for more than half a century, producing three sons and two daughters.

A generation later, both of Joséphine Charlotte’s daughters would anchor their veils with the Congo Tiara for their religious wedding ceremonies: Princess Marie Astrid wed Archduke Carl Christian of Austria in February 1982, and Princess Margaretha (pictured above) married Prince Nikolaus of Liechtenstein a few weeks later.

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The tiara was also the wedding diadem of choice when Maria Teresa Mestre y Batista married Joséphine Charlotte’s eldest son, the future Grand Duke Henri, in Luxembourg in February 1981. Henri and Maria Teresa, who are now the reigning grand ducal couple in Luxembourg, were college sweethearts.

Although the piece has been used four times as a bridal diadem, it has generally been worn more often as a necklace than as a tiara. Above, Joséphine Charlotte wears the necklace with the Belgian Scroll Tiara during a banquet held the night before the wedding of her brother, King Baudouin, in December 1960. (She’s escorted here by her husband, Grand Duke Jean, and her youngest brother, Prince Alexandre of Belgium.)

Here, for a gala event in 1967, she pairs the necklace with the grandest sparkler in the grand ducal vaults, the Luxembourg Empire Tiara.

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In November 1976, the necklace made an appearance during a state visit from Queen Elizabeth II of the United Kingdom and the Duke of Edinburgh. For this occasion, she wore the necklace with another convertible jewel, the Emerald Peacock Necklace Tiara, as well as diamond and emerald earrings from the collection of her mother, Queen Astrid of Belgium, and an emerald and diamond brooch.

It’s been quite some time since we’ve seen the necklace/tiara worn in public, in part because the Luxembourgish grand ducal family narrowly escaped losing the sparkler entirely a few years ago. Dividing up Joséphine Charlotte’s effects after her death in 2005 proved to be problematic, and the family quietly arranged the sale of many of her jewels, including this tiara. When the press found out about and reported on the planned auction, the public reaction was so overwhelmingly negative that it compelled the family to cancel the sale. (A significant number of jewels, however, were still quietly sold later.) But the necklace/tiara still hasn’t been used on a regular basis since, and all of the family’s brides in recent years have chosen to wear other tiaras, including the family’s two floral tiaras.