Pearls are the most perfect spheres in nature, with their shape determined by their ability to rotate as they grow, a study released in Spain found.

The study was conducted by scientists from the University of Granada in southern Spain, the Andalusian Earth Sciences Institute and France's University of Nancy.

If the front of a pearl grows vertically, the addition of particulates causes rotation around a single axis, leading to the formation of so-called "pearl drops," the University of Granada said.

Random growth, however, leads to spherical shapes, the researchers said. EFE