It is an ______ which may be brown, green or black in colour.

Petroleum is a very important mineral. It gives us heat and light. It also gives us power for our cars, planes, and ships. It gives us power for machines of all kinds.
     How was petroleum created? Scientists believe petroleum was formed from the remains of plants and animals. These plants and animals lived and died millions of years ago. Remains are what is left after a plant or animal has died.
     What exactly is petroleum? Petroleum is a mineral that is a mixture of hydrocarbons. It is an oily liquid which may be brown, green, or black in colour. The word "petroleum" comes form Latin and Greek. It means "rock oil".
     Crude oil is petroleum that comes directly from deep in the ground. It is then taken to a refinery. A refinery is a kind of factory with equipment in it to refine oil. At a refinery the crude oil is purified and separated into its various parts. From the refined petroleum we obtain important products, such as gasoline, kerosene, fertilisers, detergents, plastics, drugs, and perfumes. These are just a few of the thousands of useful products we get from this valuable mineral-petroleum.