Iron is named from the Anglo-Saxon iron, while the chemical symbol is derived from the Latin ferrum. The use of iron is prehistoric and there is reference to iron in the book of Genesis in the Bible. Iron is a relatively abundant element in the universe. It is found in the sun and many types of stars in large quantity. The metal is the fourth most abundant element, by weight, making up the earth's crust. The core of the earth is thought to be largely composed of iron. The most common ore is hematite from which the metal is obtained through reduction with carbon. Iron is a vital part of plant and animal life and appears in hemoglobin. It is not typically used as the pure metal, but is alloyed with carbon and other metals. Iron is the cheapest, most abundant, useful and important of all the metals.