Nontronite

Al_0.536Fe₂H₂Na_0.5O₁₂Si_3.464

Manceau, A.Chateigner, D.Gates, W. P.

Physics and Chemistry of Minerals (1998) 25, 347-365

a=5.277Å   b=9.14Å   c=9.78Å

α=90°   β=101.0°   γ=90°