I bought a package of these blades to use to help cut the roots on a stump of a tree in my yard. The good news is that the stump is out. The bad it took 2 blades to do the trick. Ice hardened or not, the blades don't cut rocks. The teeth are still there but they are not sharp. These blades have a 5 year warranty, but I don't see how they'd last that long... Back to my story, when I hit a small rock, sparks flew, dirt spewed, roots still cut though.