Celestial Connections: Understanding Black Opal's Influence on Zodiac Signs Black Opal is an exceptional assortment of dim-shaded opal gemstones. Opal is known to be a favored and natural gemstone. It is a stone that plays a shifting of colors and symbolizes faith, hope, and purity. Opal is classified as a mineraloid, which is why it is viewed as a mineral, not a precious stone. Black Opal is a water-based gemstone with silica.