A 29Si - 27Al magic angle spinning NMR study of natural silica glass from Egyptian desert

Samples of impactite glass, known as Libyan Desert Glass (LDG), were analyzed by NMR MAS in order to study the coordination of silicon and aluminum. In all samples, silicon was observed in a fourfold coordination. A very small amount of aluminum in fourfold, fivefold and sixfold coordinations was also observed in the three studied samples. The occurrence of five and six coordinated aluminum may be due to high pressure effects or due to the presence of Al-enriched micro-domains.