Abstract: A differential interferometric ballastic gravity measurement apparatus and method for measuring differential gravity between separate points employs at least two separate gravity sensors having respective free-fall masses capable of independent operation, an arrangement mounting the gravity sensors independent of one another in respective self-leveling states and at separate locations, a fiber optic-guided laser light interferometer coupled to the gravity sensors and adapted to produce a light signal indicative of a single measurement of differential gravity between the separate locations where the gravity sensors are situated, and a processing control system coupled to the gravity sensor and fiber optic-based laser light interferometer for activating independent operation of the gravity sensors and interferometer and for detecting the light signal and producing an electrical signal representing the measurement of differential gravity between the separate locations.