Minerals are abundant in nature. Five traits must be true to be a mineral. 
It must be solid and occur on earth naturally. A mineral can't be derived from a living thing. The chemical formula can't change. Finally, the atoms must form a crystal structure.  Minerals are identified by color, luster, streak (powder), fracture and hardness. 

Two examples of classes of minerals are silicates which is the largest group making up 95% of the earth's crust and upper mantle. Microcline feldspar is a silicate. Halides are minerals made from metal and fluorine, chlorine, iodine or  bromine. Table salt is a halide.
Source: National Geographic Kids Rocks and Minerals by Nancy Honovich