Lustre describes the appearance of the surface of a gemstone. For example, a diamond is said to have an adamantine lustre. The word lustre traces its origins back to the Latin word lux, meaning "light", and generally implies radiance, gloss, or brilliance.
Other descriptive terms used for gems include metallic; for example pyrite has a metallic lustre. Vitreous, like glass; resinous, like amber; waxy, like jade; greasy, like soapstone; pearly; and silky.