_____________ is referred to as black gold.

____________ increases the strength of steel.

When the mineral deposits are buried deep below the surface of the earth, ___________ is carried out.

____________ play an important role in the development of human life.

_____________ satisfies world's half requirement of energy.

The ___________ minerals certain metal in raw form.

____________ is a mineral made up of a series of plates or leaves.

_____________ is also known as atomic energy.

___________ is a hard, black and compact coal.

_____________ has a high moisture content of about 35%.