tlbuser, Wineslob thanks for the hardfacing welding rod tip, hadn't heard of them before. I did talk to the other buy who is using the wood splitter wedges on a stone splitter and he said they eventually reach a certain dull state and just stay that way (and work fine). So I was thinking maybe they work harden a bit over time.
JJ I think you are looking at an edge that hasn't been put through the splitter yet. In the last picture the edge that was split is facing the camera of the stone on the left.