Important (question on k12 test)
which choice tells the two main ways minerals are classified?

chemical makeup and crystal lattice structure

how they can be used and the country they are found in

chemical makeup and how they can be used

how they can be used and how rare they are

chemical makeup and crystal lattice structure

Explanation:

The minerals are the inorganic substances that are extracted beneath the earth crust. These minerals are associated with the gangue particles that are required to be removed by processing.

The minerals can be classified on the basis of the chemical and physical properties. The chemical properties define the chemical composition of the mineral. The physical properties define how minerals react with the external environment.

Thus chemical makeup and crystal lattice structure can be a useful approach to classify the minerals as the minerals may differ chemically as well as in structural makeup.    

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.