Green color substance forming during electrolysis

A green-colored substance formed during electrolysis, wherein the electrolyte was magnesium sulfate and minerals in tap water. 


I did not have any leads to stick into the water, so I just put a 9 volt Duracel battery in the solution. The battery didn't leak.


White flakes formed after 1 minute before green substance at 10 minutes. 
So, **what is the green stuff and what are the white flakes?**




The green material is probably an iron(II) salt, corroded from what I assume is the steel composing the positive pole of the battery. If it has a gelatinous appearance, and slowly turned orange-ish over time, my guess would be it's [$\ce{Fe(OH)2}$](https://en.wikipedia.org/wiki/Iron(II)_hydroxide), with any orange color deriving from slow oxidation to various iron(III) species such as the [oxide-hydroxides](https://en.wikipedia.org/wiki/Iron(III)_oxide-hydroxide).


Per the above link, the white flakes are possibly that same iron(II) hydroxide, prior to reaction with $\ce{O2}$ to form the green color. Alternatively, it could be [$\ce{Mg(OH)2}$](https://en.wikipedia.org/wiki/Magnesium_hydroxide), or a related magnesium compound, formed at the cathode (negative terminal) from the hydroxide ion produced by reductive water electrolysis:


$$
\ce{2 H2O + 2 e- -> H2 + 2 OH-}
$$


A photograph would be tremendously helpful in facilitating identification.


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