Is this fossil? Or iron minerals?

[FrostbyteFossils]

Found in NSW Australia. Is it a fossil or just an interesting iron mineral?

[caldigger]

This may or may not have been something biological that served as the nucleus for this concretion. But identifying it might be difficult. Perhaps someone can recognize it. 

[FrostbyteFossils]

Thanks for replying. Im very curious to find put what this is aye.

[Aurelius]

I suspect that what we see here is purely geological.

[FrostbyteFossils]

Yeah i thought so. Looks kinda pretty. Also i noticed that when i first cracked it open the centre was quite bright, but has since oxidized. Pretty interesting.