Differences between structures of ettringite and thaumasite arise from the columns of cations and anions : Ettringite cation columns are composed of Ca 3 [ Al ( OH ) 6 ?2H 2 O ] 3 +, which run parallel to the " c " axis, and the other columns of sulfate anions and water molecules in channels parallel to these columns.
22.
The crystal showed five prism faces of the form " m " { 100 } and a small face " a " { 110 }, with no pyramidal or basal faces, upon x-ray diffraction a Lauer gram along the " c "-axis revealed a hexagonal axis with vertical planes of symmetry, this study showed that the structure has a hexagonal and not a rhombohedral lattice . further studies conducted on synthetic ettringite by use of x-ray and powder diffraction confirmed earlier assumptions and analyses.
