Trying to synthesize and crystallize iron (iii) ammonium sulfate

I've been following instructions (from [here](https://en.crystalls.info/Iron(III)-ammonium_sulfate), the first method) to synthesize iron (iii) ammonium sulfate and crystallize it. The first attempt was a fail, I spilled most of my solution and what I managed to save crystallized green from a dark yellow-brown solution. I tried again, first reacting the iron (in the form of filings) with the sulfuric acid, then adding the ammonium nitrate dissolved in water and allowed to warm to room temp. There was no immediate reaction when I added the amm. nitrate but the solution changed color slowly over the next few days to a dark green-yellow. When crystals finally started forming, they were green. NH4Fe(SO4)2•12H2O should crystallize out as a pink/purple color, whereas the iron (ii) compounds crystallize green, with the regular sulfate being blue-green and Mohr's salt being a darker green. I believe I got the latter.


Basically I'm confused as to why I seem to have gotten iron (ii) ammonium sulfate rather than the iron (iii) variant. I'm going to try again for iron (iii) but with sulfates or iron (ii) and ammonium to start, I just had ammonium nitrate on hand. I can put up pictures of the crystals that I got from any of these solutions, if it might help identify. My plan is to just keep an eye on them. Mohr's salt is stable on air, so I'll watch to see if it degrades over time.


Edit: I noticed the crystals turning brown so clearly I only got iron (ii) sulfate and it's oxidizing to iron (iii) sulfate. I redissolved them in about 25% sulfuric acid and I'm going to recrystallize. To be fair the procedure for the method I used wasn't super clear.


