Minerals of Earth´s Crust

                                                                Vocabulary#11
mineral: a solid material of Earth´s crust with a definite composition.

luster:the way light bounces off a mineral´s surface.

streak: the color of the powder left when a mineral is rubbed against a hard ,rough surface.

hardness: how well a mneral resist´s scratching.

cleavage: the tendency of a mineral to break along flat surfaces.

ore :a mineral containig a useful subtance.

gem: a mineralvalued for being rare and beatiful

nonrewable resource:a resouce that cannot be replaced ithing a short period of time or at all.