Hydrated MgO smoke crystals from cubes to octahedra

Upon dissolution in liquid water at neutral pH, the cubic MgO smoke crystals give rise to octahedra with (1 1 1) facets, an evolution which is fully consistent with theoretical predictions. The first changes to show up during the dissolution process are jagged (1 1 0) cuts of the 〈1 0 0〉 cube edges. Then, (1 1 1) cuts develop at the cube corners till they become the dominant features of the dissolving crystals.