Mg(OH)(2) nanobelts with a length of 1.5-3.0 mu m, a width of 200-250 nm and a thickness of 40-50 nm were formed by treating magnesium oxysulfate(5Mg(OH)(2)center dot MgSO4 center dot 3H(2)O, abbreviated as 513MOS) whiskers in 0.5molL(-1) NaOH solution at 200 degrees C for 2.0h. The mechanical mixture model was employed to estimate the standard Gibbs free energy of 513MOS and the mechanism involved in the hydrothermal conversion from 513MOS whiskers to Mg(OH)2 nanobelts was discussed thereafter. (C) 2007 Elsevier B.V. All rights reserved.