Thanks, Isabelle, for pointing out Hereditary Grand-Duchess Stéphanie's pearl and diamond earrings. Subtle, discreet, but really elegant, and perfectly appropriate for day occasions.
Stéphanie wore these earrings on the day of her civil wedding with Guillaume, on 19th October, 2012:
(Credit: Grand-Ducal Court of Luxembourg and Pascal Le Segretain/Getty Images Europe, via Zimbio.com)