The ability to recycle aluminum (or glass, or plastic) is ultimately an illustration of

The Law of the Conservation of Mass

The right answer is The Law of Conservation of Mass

This law, discovered by Lavoisier, states that mass is neither created nor destroyed in chemical reactions or physical transformations, that means that the mass of the products is the same as the mass of the reactants. Basically, it explains that the mass of any initial element of the reaction will equal the mass of the element when the reaction comes to an end.