Hi, If a deck was being made out of this stuff, it seems very unlikely to be desert Ironwood! Desert Ironwood is beautiful, but I thought it only comes in awfully small pieces. Given the current popularity, ( and relatively low cost) of tropical hardwoods for decks, my own guess would be some South American import. Ipe comes to mind and looks something like the second set of pics. In addition, one of the big importers of Ipe does business as "Ironwoods" Anyway, anything that dense will probably make a bow if the grain is straight. Hawkbow, you might want to look up some of the threads on baking bows out of Ipe, or get a copy of the back issue of Primitive Archer with the article on making bows of Ipe.
Ron
PS Looks like somebody else is thinking along the same lines.