Iron

Iron is a relatively abundant element in the universe, found in stars and planets in considerable quantity, with very stable nuclei. Planetary cores and crusts typically contain iron, as do some asteroids. 

Iron is a vital constituent of plant and animal life, and appears in the blood hemoglobin of some species, such as Humans, causing blood to be colored red when exposed to oxygen. The other major type of hemoglobin that is not based on iron is one based on copper. Unique to the humanoid Acamarians, however, is hemoglobin that is a rare iron-copper composite. 

When the metallic form of iron is exposed to oxygen, it turns into ferric oxide (FeO2), a process and a resultant substance known generally as "rust". An iron oxide layer also existed beneath the surface of Mars. 

The asteroid that hit Terra Nova in 2083 contained Iron. 

Iron can be used for many practical, ceremonial, and decorative purposes. For example:
 * The persona of Kamin, temporarily assumed by Jean-Luc Picard in 2368, was a respected iron weaver in his community.
 * Deputy Führer Melakon presented a medal of honor - the Iron Cross, second class - to Daras in 2268.
 * A torture device made of iron in the general shape of a person and designed to impale a Human placed inside it on iron spikes was called an "iron maiden"..
 * Iron was used extensively in buildings ("ten times what you'd expect to see") by a planet suffering from frequent earthquakes due to interference from the USS Voyager.
 * An iron device for attaching and removing bolts securing tires to cars was called a "tire iron". It was sometimes brandished as a weapon because of its weight and length.
 * Early firearms were made partially of iron, and sometimes were referred to as "shooting irons" during 19th century Earth in an era known as the Ancient West.
 * Anvils were traditionally made of iron on Earth. While not their intended purpose, their heavy iron mass could be used to provide a low-intensity magnetic-field core as the basis for a subspace phase discriminator.
 * An iron filing was used by Picard in 1893 to send a simple message to Data in 2369.