Luster (mineralogy)

Luster (or lustre) is a description of the way light interacts with the surface of a crystal, rock, or mineral. For example, a diamond has an adamantine lustre and pyrite has a metallic lustre. The term is also used to describe other items with some kind of sheen (for example, fabric, especially silk and satin, or metals).
The word lustre comes from the Latin word lux, meaning "light", and generally implies radiance, gloss, or brilliance.