Fe(OH)3(a) or Goethite

[pia said]

Hi I'm modeling Fe precipitation with the addition of calcite. In my model I considered calcite dissolution (with kinetics) and Fe(OH)3(s) formation (with kinetics to). Now I’m trying to improve my model so I would like to incorporate FeOOH formation. Looking for information about the goethite formation I realized that I don't know what specie is predominantly or what specie occurs first. So I don't know what the best option is:
1. to consider just Fe(OH)3(s) formation
2. to consider just FeOOH formation
3. to consider FeOOH and Fe(OH)3(s)
I read the forum Grundl and Delwiche papers but I'm still in doubt

If someone can help me I would be very grateful