Local environments of all constituent elements (Si, Al, O, Mg, and Ca) in an amorphous slag were examined using multi-nuclear solid-state NMR under high magnetic field (16.4 T). The amorphous slag framework structure can be generally described as a depolymerized, chain-like network of SiO4 tetrahedra branched with AlO4 tetrahedra. O-17 multiple-quantum magic angle spinning (MQMAS) spectrum demonstrated that oxygens occupy structurally inequivalent sites, depending on their bonding nature. Mg-25 and Ca-43 MQMAS spectra also showed multi-site occupancy of the ions, and the average coordination numbers were estimated to about 6 and 7, respectively. Our results should underscore the impact of the high magnetic field NMR techniques, especially MQMAS, when applied to non-crystalline solids. (C) 2007 Elsevier B.V. All rights reserved.