Answer:
Luster refers to a characteristic, which helps in finding how the mineral reflects light. It gives an indication that how shiny the mineral is. The two prime ways by which the geologists classify the luster of a mineral is by differentiating it into non-metallic and metallic minerals.
The luster of a mineral differs enormously from a sample to a sample. The metallic minerals shine like metal, while the non-metallic mineral differs very much in their look. There are various distinct demonstrations of non-metallic luster. Some of these are earthy, pearly, glassy, and greasy.
Greasy luster appears like a mineral, which is covered with grease, pearly luster is iridescent, that is, glows like a pearl. The earthy luster minerals exhibit a dull appearance with no shine, and the minerals of glassy luster appear like fragments of a broken glass bottle.