Thermodynamic formation of amorphous Mn oxyhydroxides in PHREEQC?

[peterwadeuk]

Greetings good people,

I am looking for ways of predicting the formation of manganese oxyhydroxides in PHREEQC and have drawn multiple blanks when perusing the available literature.

Does anyone have any advice I could act on?

I would be most grateful.

Best wishes,
Peter

[dlparkhurst]

I think the thermodynamically stable phase in the presence of dissolved oxygen should be Pyrolusite, but under rapidly oxidizing (supersaturated) conditions the less stable phase Pyrochroite may form first.

Intermediate Mn(III) and mixed Mn(III)/Mn(IV) phases are Hausmannite and Manganite. I assume these might form by reducing MnO2 minerals.