Neltnerite

Ca_0.95Mn_6.05O₁₂Si

de Villiers, J. P. R.Dobson, S. M.Buseck, P. R.

European Journal of Mineralogy (1991) 3, 567-573

a=9.468Å   b=9.468Å   c=18.862Å

α=90°   β=90°   γ=90°