Some natural resources are nonrenewable and some are renewable. Nonrenewable resources are those that become depleted more quickly than they naturally regenerate. One example of a nonrenewable resource is mineral ore. Once mined and used completely, it is gone forever for all practical purposes, because it will take millions of years to regenerate. Renewable resources can be replenished at approximately the same rate at which they are used (for example, sun and wind, which can be used to provide energy).