SOLID-STATE NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY OF MINERALS

Abstract

Nuclear magnetic resonance (NMR) spectroscopy has been a useful tool for examining the structure of molecules in solution since the 1950s. It has only been since the late 1970s and early 1980s, though, that developments in very high field superconducting magnets and magic-angle sample-spinning (MASS) have made NMR routinely useful for examining the structure of solids. In this paper, we briefly review the theory of MASS NMR spectroscopy and some of the recent experimental results for minerals. N MR spectroscopy examines the local structural environment of atoms, to at most the third and fourth nearest neighbors. For crystalline silicates, silicon-29 and aluminum-27 MASS NMR have already proven useful in examining the validity of the aluminum avoidance principle and the extent of Al(4)/Si order/disorder, in determining the extent of polymerization, in determining the number of crystallographically distinct silicon sites present, in estimating bond strength sums and Si-O-(Si, AI) bond angles, and in detecting the presence of Al(4) and Al(6) and estimating Al(4)/Si and Al(6)/Al(4) ratios. As the NMR behavior of more nuclides (certainly including boron-H, nitrogen-IS, oxygen-17, fluorine-19, sodium-23, magnesium-25, and phosphorus-31) becomes better understood, we feel that this method will become a powerful tool for examining the local structural environment of a wide variety of species in a broad range of