The birthstone for June.  Along with amber and jet, pearl is an 'organic gem', meaning that it's not simply a mineral material but has been created from or by a living organism.  When a mollusk gets sand or another foreign body stuck inside its shell, it soothes the irritation by coating the speck with layer upon layer of iridescent nacre - this is how pearls, of various shapes, sizes and colours, are formed. Because of these origins they are considered gems of nurturing, nourishment and healing.