A review of the todorokite–buserite problem: implications to the mineralogy of marine manganese nodules: discussion

The author agrees that todorokite is a valid mineral species. However, previous comparisons of todorokite and psilomelane (romanechite) are criticized. In addition, the lower-valence manganese ions in psilomelane cannot be Mn²⁺ but must be Mn³⁺ ions, which explains the extraordinary coordination of the position M2 in the psilomelane structure as Jahn–Teller distortion.

Lattice imaging in hollandite and psilomelane on synthetic material is discussed and confirmed as showing the tunnels with Ba²⁺ ions as earlier published. In the case of todorokite, however, the published and accessible data are not convincing and contradict X-ray diffraction and other data. Experimental evidence from the synthesis of hollandite and psilomelane also makes it unlikely that the proposed large tunnels in the previous speculations on the todorokite structure can be stable. The content of these tunnels is also in doubt. It is emphasized that the reduction of Mn₇O₁₃ · 5H₂O to γ-MnOOH has been checked by X-ray diffraction methods totally independent from electron microscopy.