AM_NaNa2Mg5Si8O21(OH)3 Formula: Na3 Mg5 Si8 O24 H3 Name: NaNa2Mg5Si8O21(OH)3 Unit cell: 9.883 54.082 5.277 90.045 103.068 89.96 , V=2747.47 Space group: C-1 (2)

Camara F , Oberti R , Della Ventura G , Welch M D , Maresch W V , American Mineralogist , 89 (2004) p.1464-1473, The crystal structure of synthetic NaNa2Mg5Si8O21(OH)3, a triclinic C-1, amphibole with a triple-cell and H excess, Note: occupancies unreported, so calculated formula has an extra OH