Using a recently developed NMR technique, which involves aerodynamically levitating the sample and heating it with a CO 2 laser in the bore of a conventional NMR spectrometer, we have obtained 27 Al NMR spectra of liquids along the silica-alumina binary join at temperatures above 2000°C. All of the NMR spectra obtained contain a single Lorentzian shaped line with FWHM on the order of 10 2 -10 3 Hz. Isotropic chemical shifts become slightly more positive (less shielded) with increasing Al 2 O 3 from 56.3 ppm for the 10 mol % Al 2 O 3 liquid to 59.5 ppm for pure Al 2 O 3 liquid. Molecular dynamics simulations of SiO 2 -Al 2 O 3 liquids indicate an increase in the average coordination number of oxygen about aluminum with increasing Al 2 O 3 , with significant proportions of AlO 5 groups in the alumina-rich liquids. The slight variation in chemical shift is most probably due to opposing effects of average Al coordination and Si/(Si + Al) ratio (next-nearest-neighbor environment). For the high alumina containing liquids (mol % Al 2 O 3 > 50), 27 Al NMR lines are fully narrowed (FWHM 100-200 Hz). Below 50 mol % Al 2 O 3 , lines broaden with increasing SiO 2 content, to near 700 Hz for the 20 mol % Al 2 O 3 liquid. This observation is interpreted as due to decreasing spin-lattice relaxation times as the silica content is increased. Correlation times (τ c ) for spin-lattice relaxation calculated from the observed NMR linewidths are in good agreement with shear relaxation times (τ v ) determined from viscosity measurements of these liquids especially at high alumina content. © 1992 American Chemical Society.