Why don't rocks have lustre?

Rocks themselves do not have lustre because they are composed of multiple minerals, each with its own surface characteristics. Lustre refers to the way light interacts with the surface of a material, and since rocks are typically rough and uneven, they scatter light rather than reflecting it uniformly. Additionally, the presence of various mineral types and their textures contribute to the overall appearance, making it difficult for rocks to exhibit a distinct lustre like that of individual minerals or gemstones.