A Mineral may be defined as a homogenous substance produced by the processes of inorganic nature having a chemical composition and physical properties which are constant within narrow limits. Its structure is crystalline. It is composed of the same substance throughout. Except for impurities it has the same chemical formula for all specimens of the mineral. Its atoms usually have a definite and ordered crystal structure.
Minerals often occur in geometrical forms bounded by plane surfaces.
An orderly and symmetrical atomic structure. A definite external geometrical shape bounded by plane faces. No regular atomic structure. No tendency to assume a definite external shape. Properties which are the same in all directions.