This method is much less common, and produces, for example, 15% of minerals in the United States
It requires a wide area
It consists of digging tunnels or shafts into the earth to reach buried ore deposits
This method is more expensive than the other
This method gained popularity throughout the 20th century
The majority of this method (type of minerals extraction) occurs in North America
It causes a serious impact on the environment.
This method generates more risks to workers than the other
This method requires horizontal, diagonal or vertical accesses
With this method, big machines can be used.
