We had a lovely time at the beach this weekend playing with the Moeraki Boulders. These boulders form the same way pearls do when they form around a particle in an oyster. Fossil shells, bone fragments and scrap pieces of wood are the particles in which these boulders formed. They are made out of calcite. The boulders lose their shells when they experience the weathering effect of the ocean. The larger boulders took around four million years to form.