nonlustrous

Nonlustrous is an adjective used to describe surfaces or materials that lack luster, i.e., they do not reflect light in a bright, shiny way. In mineralogy and materials science, luster is a qualitative property that characterizes how a mineral or surface reflects incident light. Nonlustrous materials exhibit dull or matte appearances and diffuse, rather than specular, reflection, often appearing earthy or chalky. The term is used to distinguish such surfaces from lustrous or glossy finishes, such as metallic, vitreous, or resinous lusters, as well as from pearly or silky appearances.

Nonlustrous can arise from intrinsic material properties (for example, a nonmetallic mineral with earthy luster) or from surface condition (oxidation, weathering, roughened texture, or a matte coating). It does not imply the absence of all light reflection but rather the absence of bright, mirror-like reflection. In practice, observers assess luster visually, sometimes aided by reflectance measurements; a sample may be described as nonlustrous if its reflected light is diffuse and lacks sheen. The term is often used alongside related descriptors such as dull, matte, earthy, and other nonmetallic luster classifications.