Oregon Revised Statutes Revenue and Taxation § 308.115

(1) Whenever any mineral, coal, oil, gas or other severable interest in or part of real property is owned separately and apart from the rights and interests owned in the surface ground of the real property, such minerals, coal, oil, gas or other interest or parts shall not be assessed and taxed.

(2) Notwithstanding subsection (1) of this section, if the property is actively being mined as of the assessment date, the severable interest described in subsection (1) of this section shall be assessed and taxed as real or personal property in accordance with existing law in the name of the owner, separately from the surface rights and interests in the real property and may be sold for taxes in the same manner and with the same effect as other interests in real property are sold for taxes.

(3) Whenever any building, structure, improvement, machinery or equipment is owned separately and apart from the land or real property on which it stands or to which it is affixed, such building, structure, improvement, machinery or equipment shall be assessed and taxed in the name of the owner.

(4) Nothing in this section alters the tax-exempt status of a mining claim described in ORS 307.080.