Abstract The geomagnetic gradiometer is a new geophysical prospecting tool which measures directly the vertical gradient of the earth's magnetic field and the total field intensity. The system is composed of two simultaneously recording, optically pumped and monitored magnetometer sensors suspended from a helicopter. The sensors are separated vertically by a known distance so that the magnetic gradient can be determined from the difference in total magnetic intensity between the two sensors. Since the gradient is measured directly, the gradiometer allows geophysicists to make better use of LaPlace's and Euler's equations. The gradiometer increases the value of magnetic prospecting by: (1) greatly increasing resolving power, (2) discriminating between intrabasement and suprabasement anomalies, and (3) eliminating problems caused by diurnal variations.