Ettringite

Al₂Ca₆H₆₆O_49.68S₃

Moore, A. E.Taylor, H. F. W.

Acta Crystallographica, Section B (1970) 26, 386-393

a=11.26Å   b=11.26Å   c=21.48Å

α=90°   β=90°   γ=120°