The Queen’s birthday was marked this year by a scaled-down Trooping the Colour ceremony at Windsor Castle, but the pomp and pageantry was as impressive as ever. The Queen chose to re-wear the mauve floral dress coat and hat that she chose for the State Opening of Parliament in May, accessorising with an aquamarine brooch that belonged to her mother.

The combination of mauve and sky-blue aquamarine is a familiar one: for the State Opening of Parliament, Her Majesty wore a pair of aquamarine and diamond Boucheron brooches that she was given by her parents for her 18th birthday. It’s quite possible that the choice of aquamarine and diamond for her birthday was influenced by the aquamarine brooch that belonged to her mother, which is a similar Art Deco design.

Created in the 1930s, it features a large central emerald-cut aquamarine, surrounded by a symmetrical arrangement of emerald- and oval-cut aquamarines, interspersed with diamonds. The Queen Mother wore it in the 1930s and 1940s, a time when houses such as Cartier used a lot of aquamarine in bold, geometric designs.

The Queen inherited the brooch when her mother died in 2002, but did not wear it in public until 2014, when she matched it with a sky-blue coat and hat for Royal Ascot. She has worn it several times, including at a Buckingham Palace garden party in 2017, and for her annual Christmas broadcast in 2015, always pairing it with her three-strand pearl necklace and pearl earrings, as she did for this year’s Trooping the Colour parade.

Aquamarine, meaning ‘water of the sea’, is said to bring peace and tranquility to the wearer. It comes in a variety of shades, from palest, translucent blue to more vibrant duck-egg blue. The very finest aquamarines, like those in the Queen’s brooch, combine exceptional clarity with a vivid colour, and likely originate from the now-exhausted Santa Maria mine in Brazil.

Elsewhere in her collection, the Queen owns an extraordinary suite of Brazilian aquamarines in the form of a spectacular tiara, necklace, earrings, bracelet and brooch. The roots of that parure began in 1953 when the president of Brazil presented her with a necklace and earrings as a coronation gift. In 1957, she commissioned crown jeweller Garrard to make an aquamarine and diamond tiara to match, and the following year the Brazilian government gave her a bracelet and brooch to complete the set.

The Queen is not the only member of the royal family with a fondness for the universally flattering blue stone. Princess Diana owned a sizeable emerald-cut aquamarine cocktail ring by Asprey, which is now owned by Meghan Markle after Prince Harry gave it to her as a wedding gift. The Duchess of Sussex wore it as her ‘something blue’ for her wedding reception.

More recently, the Duchess wore an aquamarine necklace by Pippa Small during her controversial interview with Oprah in March. The British designer told Telegraph Luxury at the time that “ aquamarine is a very serene, positive stone. It’s the colour of the sky or the sea - it’s very freeing. It’s a hopeful stone, there’s something very pure about it.”

Read more

• The Queen’s jewellery gifts from Prince Philip, and her other most sentimental pieces

• The Queen’s Commonwealth Day brooch hides a romantic message to Prince Philip

• The best royal engagement rings through history, from the Queen to Princess Beatrice

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