Corund is a crystalline form of aluminum oxide, known for its hardness and durability. It is the second hardest natural mineral after diamond, making it valuable in various industrial applications, including abrasives and cutting tools. Corund can occur in different colors, leading to its classification into two main varieties: sapphire (blue) and ruby (red), depending on the presence of trace elements. This mineral is commonly found in metamorphic rocks and can also form in igneous environments. Corund is often mined for its use in jewelry and as a gemstone, with its brilliant luster and ability to be cut into various shapes enhancing its appeal in the market.