Luster refers to the way light interacts with the surface of a material, giving it a shiny or reflective quality. It is an important property in minerals and gemstones, helping to determine their appearance and value. Common types of luster include metallic, glassy, and pearly, each describing how light reflects off the surface. In the context of metals, a high luster indicates a polished and shiny surface, while a dull luster suggests a rough or unpolished finish. Luster can also be observed in minerals like quartz or calcite, where their unique surface characteristics contribute to their identification and classification.