Opal is a unique and colorful gemstone known for its vibrant play of colors, a phenomenon called opalescence. This occurs due to the microscopic structure of the stone, which diffracts light, creating a spectrum of colors that can change depending on the angle of view. Opals are primarily found in countries like Australia, Ethiopia, and Mexico. There are several types of opals, including white opal, black opal, and boulder opal, each with distinct characteristics. Opals are often used in jewelry, such as rings and necklaces, and are valued for their beauty and rarity. They are also the birthstone for the month of October.