Upon dissolution in liquid water at neutral pH, the cubic MgO smoke crystals give rise to octahedra with (111) facets, an evolution which is fully consistent with theoretical predictions. The first changes to show up during the dissolution process are jagged (110) cuts of the (100) cube edges. Then, (111) cuts develop at the cube corners till they become the dominant features of the dissolving crystals. (c) 2007 Elsevier B.V. All rights reserved.