Titanic at 25! All About the Film's 'Heart of the Ocean' Necklace

Photo by 20th Century Fox/Paramount/Kobal/Shutterstock

PEOPLE is celebrating the 25th anniversary of Titanic with a new special edition all about the movie, from which this story was excerpted.

It closely resembles the Hope Diamond: A massive blue stone ringed by white diamonds and dangling from a diamond-studded chain. And, like the Hope, the gem at the center of Titanic boasts a long history of owners including King Louis XIV of France. But the 56-carat Coeur de la Mer (Heart of the Ocean)—the pendant that Cal Hockley places around the neck of his fiancée, Rose DeWitt Bukater (Kate Winslet), as if it were a pricey millstone—is fictional. It does, however, enjoy the distinction of having inspired a lyric in Britney Spears' "Oops I Did it Again." I thought the old lady dropped it into the ocean in the end/ Well baby, I went down and got it for you.

The Heart figures into many Titanic plot points: Rose wears it (and it alone) when Jack Dawson (Leonardo DiCaprio) draws her portrait; Cal's valet Lovejoy plants it in Jack's pocket to frame him for theft; it lures treasure-hunter Brock Lovett's crew to the wreck site in hopes of recovering it; and finally, as Britney notes, it is plunked into the Atlantic by 101-year-old Rose, proving she never needed Cal's wealth to get by. (Though why she denies that inheritance to her very nice caretaker granddaughter Lizzy is still anyone's guess.)

With so much screen time, this fake treasure had to be spectacular. Titanic production designer Peter Lamont commissioned London jewelers Asprey & Garrard to create a few versions of the prop, with a cubic zirconia in the role of the blue diamond. The cost of a real stone of that size, "would have been prohibitive, despite our budget," he said.

RELATED: James Cameron Says Leonardo DiCaprio Nearly Lost Titanic Role Over His Attitude in Audition

When filming was finished, Asprey brought the Heart of the Ocean into reality, with a spectacular 171-carat blue sapphire and 103 diamonds. "This stone was special," Asprey's then-head of jewelry Terry Davidson told Reuters of the Sri Lankan sapphire. "It talked to you. You knew that once it was cut, it would be the heart that we wanted." He also felt it was important that its blue color "look as near as possible to the clarity of that ice-cold sea in the Arctic."

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The pendant was made with the intent that it be auctioned for charity. It went on the block in Beverly Hills at a celeb-filled gala in the spring of 1998 and sold for $2.2 million to an anonymous bidder, with proceeds going to Southern California's Aid for AIDS, and to the Diana, Princess of Wales Memorial Fund, honoring Diana, who had died the previous August.

But a bauble like that is meant to be seen. And so, by agreement with the buyer, Celine Dion wore it with a navy blue Michael Kors gown to the 1998 Oscars, where she performed the film's award-winning love theme. "The necklace came first, and we built my outfit around it," said Dion. Another nominee, Gloria Stuart who played Rose as an old woman, wore a similar oblong blue-diamond pendant from Harry Winston valued at $20 million, creating perhaps the costliest mini-trend in red carpet history. Fans, however, could pick up an authorized knockoff for about $200 from the J. Peterman company. Where might a regular gal wear such a statement piece?The catalog helpfully offered some suggestions: "Wear it to a coronation. Wear it to the movie. Wear it to bed."

The PEOPLE Titanic anniversary edition has two collectible covers.

PEOPLE's new special edition Titanic: Leonardo DiCaprio, Kate Winslet and the Making of an Epic Love Story, is available now wherever magazines are sold.