The LFMG instrument is used to make extremely high resolution scalar magnetic field and difference measurements at the Earthfs surface. The Phase 1 effort included development of a conceptual design and established the feasibility of designing, fabricating and demonstrating in Phase 2 two prototype LFMG instruments for use in a gradiometer configuration. The Phase 1 LFMG conceptual design includes a technical plan for approaching 10 fT/ãHz resolution in the LFMG prototype. The breadboard LFMG demonstrated measurements of scalar field variations with a resolution of 45 fT/ãHz in Phase 1. The LFMG has stability required to measure vector gradients (difference of scalar measurements between two LFMG instruments on the Earthfs surface) with very high stability over distances of the order of kilometers. The LFMG prototype will have a dynamic range of 25,000 nT to 75,000 nT, and achieves an accuracy and stability necessary to perform common mode noise rejection between two LFMG instruments. This advance in the state of the art represents an increase in sensitivity of more than an order of magnitude, and will permit new high performance gradiometer measurements for use in innovative exploratory research into the effects producing temporal variations in the magnetic field over the Earthfs surface.