Kate Middleton’s engagement ring is undeniably one of the most famous pieces of jewelry in the world.

Having first belonged to Princess Diana, the blue sapphire and diamond ring has been circulating on the royal scene since 1981, when the future King Charles proposed to Diana with it.

Though there’s some debate over exactly how the sapphire bauble made its way into the royal family (the jewelry company that made it, Garrard, claims Prince Charles chose it for his young bride because it reminded him of his mother’s own sapphire brooch while others say Diana ordered it from the company’s catalog or chose it from a spread of jewels that Charles presented her with), it’s been in Kate’s possession since 2010, when Prince William used it to ask for her hand in marriage.

“It’s my mother’s engagement ring, so I thought it was quite nice because obviously, she’s not going to be around to share in any of the fun and excitement of all this,” Prince William said in his engagement interview with Kate. “This is my way of keeping her sort of close to it all.”

He also told reporters of the piece: “It’s very special to me. As Kate’s very special to me now, it was right to put the two together.”

And while Princess Kate’s ring is certainly unique, she isn’t the first British royal to wear a sapphire stone on her left finger. Aside from her late mother-in-law Princess Diana, Queen Elizabeth’s mother, the Queen Mother, received a sapphire engagement ring from King George VI in 1923. Princess Anne also wears a sapphire engagement ring from her husband, Timothy Laurence.

Here’s everything to know about Kate Middleton’s engagement ring.

The ring features a 12-carat sapphire center stone

The Princess of Wales’ engagement ring boasts a huge oval Ceylon sapphire that weighs 12 carats. The blue stone is surrounded by 14 solitaire diamonds and set in 18-karat white gold.

 

It was inspired by another famous royal jewel

According to jewelry company Garrard, who crafted the family heirloom, its design was inspired by another famous piece in the royal collection: a sapphire-and-diamond brooch that was commissioned by Prince Albert in 1840 for his then-fiancée, Queen Victoria. Not only did Queen Victoria adore it (“She found she loved it so much that she decided to wear it on her wedding day as her something blue on the front of her dress,” Garrard’s creative director, Sara Prentice, told Vogue in 2017), it now belongs in the crown heirloom collection and was reportedly a favorite of Queen Elizabeth, who wore it to meet President John F. Kennedy in 1961.

 

Kate’s ring originally belonged to Princess Diana

Long before the ring adorned Kate’s finger, it was worn by Princess Diana.

The ring was reportedly one of several pieces that Charles presented Diana with at Windsor Castle ahead of his proposal, and he chose to include it because it resembled Queen Elizabeth’s sapphire brooch.

The company’s creative director, Prentice, told Vogue, “It was said to be a strong influence on Prince Charles when he came to Garrard to purchase a ring for Lady Diana. He actually ended up setting a sapphire cluster ring for her … I would imagine growing up being surrounded by your mother and your grandmother [with] such beautiful, incredible jewelry … it would stick with you.”

When Charles proposed to Diana with the ring in 1981, the jewel was priced at $37,500, though its value has increased significantly in the decades since.

 

Kate debuted her blue engagement ring with a matching dress

Royal admirers first saw the sapphire and diamond ring on Kate’s hand during the couple’s engagement announcement at St. James’s Palace on Nov. 16, 2010. Kate had the perfect ensemble to show it off in: a royal blue Issa dress with a V-neckline and a crossover waistband.

Her gold wedding band was a gift from Queen Elizabeth

The blue ring got some company on Kate’s finger on her and William’s wedding day on April 29, 2011, when Queen Elizabeth gifted the bride with a Wartski Welsh gold wedding band. Welsh gold bands are a long-standing tradition for the royal family: King Charles and Queen Camilla received similar wedding rings in 2005.

 

Kate has matching jewels for her engagement ring

While Kate’s ring is stunning enough to make a statement on its own, the Princess of Wales also has some matching pieces she has worn on occasion, which were from Princess Diana’s personal jewelry collection.

In 2019, Princess Kate debuted a large pair of double-cluster sapphire-and-diamond earrings that once belonged to Diana. The late princess was photographed wearing the jewels many times, including at the Met Gala in New York in 1996.

 

Prince William gifted Kate an eternity ring after Prince George’s birth

Three years after the couple got engaged, Kate’s show-stopping engagement ring and Welsh gold wedding band got even flashier with the addition of a white gold diamond eternity band that Prince William gifted her from Annoushka.