re: What is this?

Ok, what you have is Burr Oak. It’s considered a non desirable material to work with because it’s so hard and dense. I’ve built two pieces of furniture with Burr oak and it requires sharp tools, patience and for you to consider letting the wood tell you what it wants to be. Hand tools are the best way to work it. Power tools bind, breaking fences and injuring workers.. Be careful with it, if you have the patience you can get incredible results! Good luck!