NAICS 21 is the category within the North American Industry Classification System which is composed of establishments that extract naturally occurring mineral solids(i.e. as metals, coal and other industrial minerals), liquid minerals (i.e. crude petroleum) and gases (i.e. natural gas).
Definition of mining
NAICS 21 uses the term "mining" to include quarrying, well operations, beneficiating and other mineral preparation customarily performed at the mine sites, or as a part of mining activity and distinguishes two basic activities:
Mine operation
Mine operation includes companies that operate mines, quarries, or oil and gas wells for themselves, and companies which operate them on a contract or fee basis.