Unlocking geological time capsules with analytical chemistry

Kirsty Penkman is fascinated by opercula. They are the ‘little trapdoors’ that many snail species use to seal themselves away inside their shells, and they are Penkman’s favourite biomineral. She’s not alone – people have been collecting them for centuries and operculum jewellery was fashionable in the Victorian era – but for Penkman their appeal is more scientific than cosmetic.