Australia's national gemstone is the OPAL. The OPAL is a precious gemstone that is found in many parts of the world, but Australia is known for its unique and beautiful opals. It is the only country in the world that produces opals commercially. Opals are composed of silica and water, and they come in a variety of colors, including white, black, blue, and pink. The OPAL is a symbol of hope, luck, and protection, and it is often used in jewelry and other decorative items.