Pearls are a timeless and elegant gemstone that has been prized for centuries. They are formed when a mollusk secretes layers of nacre around an irritant, such as a piece of sand or a bit of food. The nacre is made up of calcium carbonate and a protein called conchiolin, and it gives pearls their characteristic luster and iridescence.
Pearls come in a wide variety of colors, shapes, and sizes. The most common color is white, but pearls can also be found in shades of pink, cream, yellow, green, and black. Pearls can be round, oval, baroque, or even shaped like teardrops. The size of a pearl is measured in millimeters, and the larger the pearl, the more valuable it is.