luster
Luster describes the way light reflects off of the surface of the mineral. You might describe diamonds as sparkly or pyrite as shiny. But mineralogists have special terms to describe luster. They first divide minerals into metallic and non-metallic luster. Minerals that are opaque and shiny, like pyrite, are said to have a metallic luster. Minerals with a non-metallic luster do not look like metals. There are many types of non-metallic luster. Six are described below Table below .