Answers

2015-09-03T17:34:12+05:30
Because its single drop is even valuable like the very small piece of gold.
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2015-09-03T17:39:45+05:30
Petroleum is referred to as "Black Gold" because when crude oil is extracted from the land it is black in color. People call it gold because of its oils and value . It is very difficult to find. So it is called "Black Gold".
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