Definitely Eucalyptus and well on its way to drying out by the looks of the cracking.
I have found it to be easiest to split while still green as it goes hard as heck once dried and I find it makes very good firewood. I've never tried leaving it to split when it's dry for big rounds as everybody I know says it's a nightmare....but hey if it works for you then who cares
I have done it with sub 10" rounds and to be honest a hefty wack with my splitting maul seems to do the job fine no matter how dry.
It's a fairly heavy wood when green and, I think, rather a light wood when dry giving an idea of just how much water is in the tree.
Bearing in mind there are well over 300 different species of Eucalyptus the above may vary from one to another.
Hope that helps,
Bam.