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, coffee, and forests, for example), which can restock (renew) themselves at approximately the rate at which they are extracted, if they are not overharvest ed. Non-living renewable natural resources include soil, as well as water, wind, tides and solar radiation — compare with 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 latter may not necessarily occur near the former.