The __________ minerals are the most valuable minerals.

_____________ is derived from the rocks where it flows freely in either liquid or gaseous form.

________________ is generated by using coal, petroleum and natural gas.

____________ is referred to as buried sunshine.

Heat energy obtained from the earth is called ____________ .

_____________ is referred to as black gold.

The word petroleum is derived from ____________ word.

____________ refineries act as a "nodal industry".

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

___________ is the hardest coal and ranks highest among the coals.