definition
strict definition
underground mine
A cavity or network of tunnels dug under the earth for extraction of minerals.
An underground mine is an intentionally hollowed cavity, tunnel, or network of tunnels under the surface of the earth where minerals or other substances are dug out from within.
The excavation removes substances from beneath the surface. It can be one cavity or a connected network of tunnels.
An open pit is fully exposed to the atmosphere above. The underground mine instead extends into enclosed space beneath the earth's surface.