Kate Middleton has worn some phenomenal jewelry since becoming the Duchess of Cambridge. It all began with her famous sapphire engagement ring — which belonged to her late mother-in-law, Princess Diana. Since then, Kate has worn a collection of pieces from both Diana and Queen Elizabeth that have a total worth over $100 million. But which piece is the most expensive?

Kate Middleton wearing a sash and the Cambridge Lover's Knot tiara at a reception

Duchess of Cambridge Kate Middleton | Victoria Jones – WPA Pool/Getty Images

Kate Middleton wore the Cartier Halo tiara on her wedding day

When Kate married Prince William in April 2011, she wore the Cartier Halo tiara worth an estimated $1.7 million. Borrowed from Queen Elizabeth, the tiara featured 739 brilliant-cut diamonds and 149 baguette-cut diamonds. It was originally a gift from King George VI to his wife, Queen Mary, in 1936.

Kate Middleton’s Jewelry Collection From Queen Elizabeth and Princess Diana Is Worth Over $100 Million — Which Piece Is the Most Expensive