Question

which mineral is known as black gold and why

Answer 1

Petroleum or coal because it is hard to find, very costly to extract and very valuable

Answer 2

Hey!!!   Petroleum and Coal are the minerals known as $\bf{Black Gold}$. Petroleum is very costly and also the crude oil is obtained from the ground in black colour so it is called as $\bf{Black Gold}$. Coal is also costly and black in colour so it is also called $\bf{Black Gold}$.       #BE BRAINLY