Why Kate Middleton's Cartier shamrock brooch is so important?

Princess Catherine took the salute as Colonel of the Irish Guards at St Patrick’s Day celebrations in Aldershot.

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She accessorized with a gold Cartier shamrock brooch, which has a lengthy royal history.

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[{"selector":"#anim-c1a7d331-4bcc-433b-bd04-c67a4dfa3605 [data-leaf-element=\"true\"]","keyframes":{"transform":["translate(-10.681818220708294%, 0%) scale(1.5)","translate(0%, 0%) scale(1)"]},"delay":0,"duration":2000,"easing":"cubic-bezier(.3,0,.55,1)","fill":"forwards"}] [{"selector":"#anim-c7af7414-e40c-405c-a07d-d90702888706","keyframes":{"opacity":[1,1]},"delay":0,"duration":2000,"easing":"cubic-bezier(.3,0,.55,1)","fill":"both"}] [{"selector":"#anim-2be1fff5-55a8-4438-99ba-10819866ef70","keyframes":{"transform":["scale(3)","scale(1)"]},"delay":0,"duration":2000,"easing":"cubic-bezier(.3,0,.55,1)","fill":"forwards"}] The brooch belongs to the Irish Guards and is loaned out to royal ladies associated with the regiment.

[{"selector":"#anim-73c29221-860c-4e12-97b5-baac87bba266 [data-leaf-element=\"true\"]","keyframes":{"transform":["translate(5.303030322337445%, 0%) scale(1.5)","translate(0%, 0%) scale(1)"]},"delay":0,"duration":2000,"easing":"cubic-bezier(.3,0,.55,1)","fill":"forwards"}] [{"selector":"#anim-e81a1d62-90e0-43be-ac74-7491adad7576","keyframes":{"opacity":[1,1]},"delay":0,"duration":2000,"easing":"cubic-bezier(.3,0,.55,1)","fill":"both"}] [{"selector":"#anim-7bd83aa2-91b2-4683-8d1f-3c02704910c8","keyframes":{"transform":["scale(3)","scale(1)"]},"delay":0,"duration":2000,"easing":"cubic-bezier(.3,0,.55,1)","fill":"forwards"}] Its origin is unclear, but it was reportedly designed by Cartier and gifted to Princess Mary by the regiment in 1961.

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The brooch is spun in the shape of a shamrock, the symbol of Ireland, and set with a tiny circular emerald at the center.

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