Freshwater Pearls
Pearls are formed in shellfish, especially oysters and mussels, as a natural defense against an irritant such as a piece of sand. Layers of aragonite, commonly referred to as nacre, are secreted around the irritant and gradually build up to form the solid pearl. Light reflecting from these overlapping layers of nacre produces a characteristic iridescent luster, also known as the "orient of pearl." Pearls vary in color from white, or white with a hint of color (often pink), to brown or black, depending on the type of mollusk and the water the shellfish lives. Pearls are sensitive to acids, dryness, and humidity, and so are less durable than many other gems. Pearls were once thought to be the tears of the gods.


