At the Spectre premiere, the Duchess of Cambridge wore a pair of girandole earrings. They look like they might be aquamarine or blue topaz. I hope they are real and not costume jewellery.
UPDATE: Anna N from My Small Obsessions ID'd them as blue topaz earrings by Robinson Pelham. https://twitter.com/AnnieElizabethN/status/658731737153978372 Previously worn by Carole Middleton at her daughter's wedding reception. Robinson Pelham's website describes them as "Pagoda earrings set with blue topaz and diamonds in white gold, £14,300"