ðə hˈɛksɐɡənəl fˈɔːɹm, wˌɪtʃ ɪz klˈoʊsli ɹᵻlˈeɪɾᵻd tə ðə mˌɑːnoʊklˈɪnɪk fˈɔːɹm, kəntˈeɪnɪŋ ɡˈɑː twˈɛnti fˈoːɹ plˈʌs jˈuːnɪts,  kənvˈɜːts tə ðə mˌɑːnoʊklˈɪnɪk fˈɔːɹm wɛn ɐnˈiːld æt fˈaɪvhˈʌndɹɪd dᵻɡɹˈiːz sˈiː.
The hexagonal form, which is closely related to the monoclinic form, containing Ga24+ units,  converts to the monoclinic form when annealed at 500 °C.