Catherine wore unidentified Diamond and Aquamarine Drop Earrings at the 2014 Order of Garter Service.
She again wore them at Commonwealth Church Service paired with her Erdem Gray Coat. She has a pair of sparkling earrings in her wardrobe for a long time.
They look something like shown in the picture above, but we do not have any information about its origin.
Design Your Own Regal Wardrobe.