vocabulary 14

mineral: a solid materialof 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 mineral resists scratching.

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

ore: a mineral containing a useful subtance.

gem: a mineral valued for being rare and beutiful.

nonrenewable resource: a resource that cannot be replaced within a short period of time or at all.