Perhamite

Al_7.7Ca_2.7H_12.68O_45.862P₄Si₃Sr_0.3

Mills, S.Mumme, G.Grey, I.Bordet, P.

Mineralogical Magazine (2006) 70, 201-209

a=7.021Å   b=7.021Å   c=20.218Å

α=90°   β=90°   γ=120°