Kate Beckinsale attends Leonardo DiCaprio's 49th birthday in a party dress with a familiar blue gemstone

Movie stills from Titanic, The Aviator overlaid with Instagram image of Kate Beckinsale in sapphire dress
Though the look seems to be a reference to a famous DiCaprio film, one question has persisted: Which one? Photo credit: Moviestore / Shutterstock, Cinematic / Alamy Stock Photo, @katebeckinsale / Instagram

By Jacqui Palumbo of CNN

Kate Beckinsale wore a bejewelled mini dress over the weekend to celebrate Leonardo DiCaprio's 49th birthday in Los Angeles, and a photograph of the black frock, which featured a colossal blue-gemstone-like accessory belted around her waist, has since made its rounds across the Internet.

Though the look seems to be a delightful reference to a famous DiCaprio film, one question has persisted: Which one? Is the gem a blue diamond or blue sapphire?

The former, of course, might be a nod to the one of the most famous pieces of jewellery in movie history - the fictional heart-shaped blue diamond from 1997's Titanic, worn by the other important Kate in DiCaprio's life. But being that the Heart of the Ocean is well, heart-shaped, a second possible inspiration for the look is a piece of jewellery with more direct significance to Beckinsale. In her co-starring role as Ava Gardner in The Aviator, Beckinsale declares to Howard Hughes, played by DiCaprio, that she's "not for sale," when he woos her a square-cut blue sapphire necklace. 

Whichever fictional gemstone Beckinsale made larger-than-life, the statement piece was surprisingly not a custom look for the event, but straight from The Blonds Fall-Winter 2023 collection, which showed during New York Fashion Week in February.

Inspired by films such as Valley of the Dolls and the jewellery worn by stars like Elizabeth Taylor, the collection - by designer Phillipe Blond and creative director David Blond - was an exuberant, campy celebration of Hollywood glamour, bursting with sculptural corsets, velvet gowns and sequined party dresses that included oversized gemstone motifs.

For her night out, Beckinsale paired the ultra-mini with black tights - a near continuation of the pantsless trend, as the runway version of her look was presented slightly shorter as a top - sky-high reflective platform heels and a big black hair bow.

Other attendees to the Beverly Hills fête included Beyoncé and Jay-Z, Salma Hayek, Kim Kardashian, Zoë Kravitz and Channing Tatum, according to Harper's Bazaar. But no one else seemed to celebrate the occasion with such a chic sartorial easter egg, leaving Beckinsale's look a dazzling win for the night.