Chrysoberyl is a mineral composed of beryllium aluminum oxide, known for its hardness and durability. It typically forms in metamorphic rocks and can be found in various colors, including yellow, green, and colorless. The most famous variety of chrysoberyl is alexandrite, which changes color depending on the light source. This gemstone is valued for its brilliance and is often used in jewelry. Chrysoberyl has a hardness of 8.5 on the Mohs scale, making it one of the hardest gemstones available. Its unique optical properties and rarity contribute to its appeal among collectors and gem enthusiasts.