Abstract: A method for determining the nuclear magnetic resonance longitudinal magnetization decay of formations surrounding an earth borehole that involves: providing a logging device moveable through the borehole; applying a static magnetic field in the formations to align spins in the formations in the direction of the static magnetic field; producing a tipping pulse for tipping the direction of the spins with respect to the static magnetic field direction; and detecting the time varying magnitude of the spin magnetization as the magnetization returns toward the static magnetic field direction; the longitudinal magnetization decay being determinable from the detected time varying magnitude of the spin magnetization. Related methods and apparatus for implementing these methods are also described.