a Mallee root would have to be the worst of them rocks & sand & what not embedded in it
& a large amount of Mango trees in Queensland in Aus have star pickets, nails & other metal oject in them as the star pickets would get encased by the tree and the iron nails etc were meant to help them fruit was the theory
its just awesome to hit a nail with your chainsaw let alone a star picket to make you invest in a new chain