The distance between boreholes drilled for exploration or sampling purposes. With bedded minerals, the holes may be positioned at the intersection points of coordinates or at the corners of equilateral triangles with sides from 30 to 200 m apart. The spacing is closer with patchy deposits. With metallic ores following belts across country, the holes are spaced along lines crossing the orebody in order to yield cross sections of the ore at definite intervals. In the case of known and semiproved coalfields, boreholes at 1/2- to 1- km intervals may suffice.