If a mineral has a metallic shine to it, the luster of the mineral is being measured.
Luster is the property of a mineral which describes how the mineral reflects light, and also the dullness or brightness of the mineral. Luster is grouped into two which are; metallic and non-metallic. Minerals with a metallic luster are reflective and opaque. An example is pyrite. Non-metallic luster are also classified into groups based on how much light is reflected. The groups include pearly, dull, waxy, resinous, silky, and vitreous luster.
