I was clearing one of my 4 wheeler trails many years ago after a wind storm we'd had. A Balsam Fir, a very low density tree, had been blown over and a root was sticking out of the ground blocking the trail so I pulled out a hand axe and started chopping at it. I was amazed at how hard and tough it was. The tree itself has a density of about .30 but from chopping on it I could tell the density of this root was well over .60. I got half way through, the root was about 4" in diameter, and tried to break it, it would not break. I though that one day I would find a suitable root and make a bow out of it, haven't done it yet but I haven't forgotten