Natural resources are commodities that are considered valuable in their
relatively unmodified ( natural) form. A commodity is generally considered a
natural resource when the primary activities associated with it are
extraction and purification, as opposed to creation. Thus, mining, oil
extraction, fishing, and forestry are generally considered natural-resource
industries, while farming is not.
Natural resources are often classified into renewable and non-renewable
resources. Renewable resources are generally living resources (fish and
forests, for example), which can restock (renew) themselves at approximately
the rate at which they are extracted. Non-living renewable natural resources
include water, wind, tides and solar radiation - compare renewable energy.
Mineral resources are generally non-renewable and, once a site's
non-renewable resource is exhausted, it is considered to be useless for
future extraction -- barring technological improvements that allow economic
extraction from the tailings.
Both extraction of the basic resource and refining it into a purer, directly
usable form, (e.g., metals, refined oils) are generally considered
natural-resource activities, even though the later may not necessarily occur
near the former.