Hello new member cdHughz, and welcome. You've found a piece of what some people call zinc alloy. Others call it the veritable hellspawn that it is; the cursed metal sent from hades to confound an already unproductive day with it's siren's song; to be plucked from the earth with anticipation, only to reveal it's putrid withered form.
anywho... looks like it might have been some sort of mounting bracket or spacer. *note: "once was" is the only correct way one describes zinc out of the ground.