The IR spectra of siliceous zeolite Y were measured as a function of external pressure. The results indicate that the siliceous zeolite Y undergoes pressure-induced amorphization. This phase transformation seems to be driven by the severe distortion of double six-membered rings joining the adjacent sodalite cages to form the zeolitic lattice. Unlike hydrated zeolite NaY and structurally related zeolite NaA, the amorphization is irreversible due to the lack of hydrated charge balancing cations. (C) 2003 Elsevier Science Ltd. All rights reserved.