Today’s aquamarine tiara is one that generally falls into either “love it” or “hate it” camps: the British aquamarine tiara with pine cone/flower motifs that is owned today by Princess Anne.
The tiara itself dates back nearly a century to Anne’s grandparents, King George VI and Queen Elizabeth. The king commissioned Cartier to make the tiara for his wife as an anniversary present in the 1940s. She was photographed in it a few times, but it was never used as much as many of her other jewels. In 1973, Elizabeth (by then better known as the Queen Mother) gave the tiara to her granddaughter, Princess Anne, as a wedding gift.
Older photographs of the tiara compared with more current pictures make it clear that changes were made to the piece some time after Anne took possession of it. The large circular element in the center of the tiara was removed; today, one of the large rectangular aquamarines sits in the center of the piece.
Anne still wears the tiara occasionally, including at the Irish state banquet in 2014. To my knowledge, this is one of the only royal tiaras (maybe one of the only pieces of royal jewelry, period) that uses pine cones as a central motif. Pine cones are a symbol of fertility, which is always a good thing in marital terms, I suppose. But Anne’s tiara isn’t the only British piece to include tree-parts in its design: remember that the Duchess of Cambridge wore earrings to her wedding that included tiny acorns in their design.