apex rule
apex rule 〈美〉(矿产法)脉顶规则 在公有土地上已确定矿区的采矿人，有权利跟踪开采其脉顶在其矿区边界内——包括在其地表或其垂直平面深处内——的任何矿脉。如其矿脉斜向延伸，超越矿区边界的垂直平面，亦仍有继续跟踪开采的权利；但最终应不得超越脉线的末端或其末端所至的垂直平面。
APEX RULE
apex rule
apex rule. Mining law. The principle that a vein of ore may be mined if it extends beyond the vertical boundaries of the surface claim on which the vein apexes. — Also termed extralateral right. Cf. INTRALIMINAL RIGHT. [Cases: Mines and Minerals 30. C.J.S. Mines and Minerals § 69.]