This amulet of polished hematite represents a headrest. The end of the base is now chipped. Such amulets were common in Late Period burials, where their magic was intended to lift the head of the deceased at the moment of resurrection.
From Giza: G 7540T, Room III [Excav. date] March 1929. Excavated by the Harvard University–Museum of Fine Arts Expedition; assigned to the MFA by the government of Egypt.
Harvard University—Boston Museum of Fine Arts Expedition