A metal with the descriptor “ferrous” means that it has iron in its composition. When the term ferrous metal is used, it also usually implies that iron is a large percentage of the elemental composition. If it’s not the most abundant element, it would probably be the second or third most prolific. If a metal only contains trace amounts of iron, as many metals do, then that small amount is not considered enough to declare the metal ferrous.http://www.glory-metallurgy.com/ferrosilicon/