Things must be different north of the equator; the only firewood I've found difficult to "split" with a standard Kelly axe (in the days when I had to) was good old mallee roots. Being lignotubers, there was no grain that ran for more than 0.5cm. But we had an advantage, I suppose; if you couldn't split a pencil line (along rather than across its length) drawn on the top of the block by the time you were 14 you were regarded as an incompetent axeman. It was a mark of superiority to split any woood, even 3' diameter lumps from the base of the tree trunk. And most of us ended up with at least one scar to demonstrate.