Selected beam geometry allows us to suppress the bulk contribution to sum-frequency generation from crystalline quartz and use sum-frequency vibrational spectroscopy to study water/alpha-quartz interfaces with different bulk pH values. The spectra are qualitatively similar to those of water/fused-quartz interfaces, but display an ice-like peak that resembles very closely that of a real ice surface, providing the first evidence to the belief that water molecules at a crystalline oxide surface form a more ordered hydrogen-bonding network. (C) 2003 Elsevier B.V. All rights reserved.