43 CFR § 3594.3 - Boundary pillars and isolated blocks.

(a) If the ore on adjacent lands subject to the regulations in this part has been worked out beyond any boundary pillar, if the water level beyond the pillar is below the operator's/lessee's adjacent operations, and if no other hazards exist, the operator/lessee shall, on the written order of the authorized officer, mine out and remove all available ore in such boundary pillar, both in the lands covered by the lease and in the adjoining premises, when the authorized officer determines that such ore can be mined without undue hardship to the operator/lessee.

(b) If the mining rights in adjoining premises are privately owned or controlled, an agreement may be made with the owners of such interests for the extraction of the ore in the boundary pillars.

(c) Narrow strips of ore between leased lands and the outcrop on other lands subject to the regulations in this part and small blocks of ore adjacent to leased lands that would otherwise be isolated or lost may be mined under the provisions of paragraphs (a) and (b) of this section.