Opal is a gemstone known for its colorful, scattered patterns that differ on each side. It is mainly found in Australia, which supplies 95% of the world's opal demand. Opals are divided into precious and common varieties, with precious opals displaying vibrant color play and common opals showing solid colors. The rarest type is black opal, followed by white opal, while common opals come in many colors but lack the dramatic color effects of precious opals. Opals are used in various types of jewelry due to their attractive colors.