A gradiometric induction sensor has been developed as a sensitive indicator of spatial electrical conductivity gradients. Utilizing a configuration of three antennas in a single, monolithic metal slot, its design is simple and compact. Its feasibility as a geometry indicator for use in oil wells drilled with oil base mud has been demonstrated by a series of laboratory experiments which simulated many borehole and logging conditions. Response to real and synthetic rock arrays, resolution, standoff sensitivity, and response to dipping geologic beds are among the issues quantified by the experiments. In addition, some useful models are presented as an aid in conceptualizing the principles behind the operation of the sensor.