Humans have long since been fascinated by pearls, and mollusks have produced them throughout evolutionary history. Romans thought they were frozen tears of the Gods, Greeks attributed them to lightning strikes at sea. They were commonly dedicated to Venus, Goddess of love & beauty. Alexander Severus, born in Africa and not to be confused with Severus Snape from Harry Potter, reportedly hung pearls in the ears of a status of Venus. They're known as the Queen of Gems... but what causes a pearl?