  In this work we present measurements of permeability, effective porosity and
tortuosity on a variety of rock samples using NMR/MRI of thermal and
laser-polarized gas. Permeability and effective porosity are measured
simultaneously using MRI to monitor the inflow of laser-polarized xenon into
the rock core. Tortuosity is determined from measurements of the time-dependent
diffusion coefficient using thermal xenon in sealed samples. The initial
results from a limited number of rocks indicate inverse correlations between
tortuosity and both effective porosity and permeability. Further studies to
widen the number of types of rocks studied may eventually aid in explaining the
poorly understood connection between permeability and tortuosity of rock cores.
