This study was to identify and evaluate known technologies employing electromagnetic resonance phenomena in solid minerals for their identification and assaying, particularly assay logging of exploratory boreholes. A literature research and study revealed some little-known, nuclear magnetic resonance (nmr) techniques developed by a group at the University of Geneva, Switzerland. These are suitable for use in weak, inhomogeneous magnetic fields. Laboratory nmr tests of numerous U.S. ore minerals showed good identifying signals from phosphates, fluorspar, bauxite, oil shale, and spodumene (lithium) ores, but not from copper, lead, antimony, or manganese ores tested. Use of electron paramagnetic resonance "signatures" for such ores is suggested. A conceptual design for an nmr assay logging system is proposed.