Ferrocerium is a man-made metallic material that gives off hot sparks at temperatures of 1,650 °C (3,000 °F) when scraped against a rough surface (pyrophoricity), such as ridged steel. Because of this property it is used in many applications, such as clockwork toys, strikers for gas welding and cutting torches, so-called "flint-and-steel" or "flint spark lighter" fire-starters in emergency survival kits, and cigarette lighters, as the initial ignition source for the primary fuel. It is also commonly called ferro rod and most commonly of all, flint (particularly in cigarette lighters).
While ferrocerium-and-steels function in a similar way to actual flint-and-steel in fire starting, ferrocerium takes on the role that steel played in traditional methods: When small shavings of it are removed quickly enough the heat generated by friction is enough to ignite those shavings, converting the metal to the oxide, i.e., the sparks are tiny pieces of burning metal. The sparking is due to cerium's low ignition temperature of between 150 and 180 °C (302 and 356 °F). About 700 tons were produced in 2000.
Comparison with traditional flint
Modern flint bears no chemical relationship to the mineral flint historically used to generate sparks. In traditional flint-and-steel fire-starting systems (using actual flint), it is the tiny shards of iron produced in the striking process that burn, not the flint.
Flint spark lighter
A flint spark lighter (sometimes just called a spark lighter, striker, or flint lighter) is a type of lighter used in many applications to safely light a gaseous fuel to start a flame. It is most commonly used for bunsen burners and oxyacetylene welding torches.
A flint spark lighter works by rapidly rubbing a small piece of ferrocerium against a rough steel surface (also called the rasp), in much the same way flint and steel are used. This manual rubbing action, done by squeezing the handle, creates a spark which then lights the gaseous fuel.
As tinder-igniting campfire starter rods it is sold under such trade names as Blastmatch, Fire Steel, and Metal-Match for survivalists and bushcraft hobbyists. Some manufacturers and resellers incorrectly call them "magnesium" rods. However, some manufacturers combine a strip of ferrocerium along with a strip of with magnesium in the same item. The idea being that you scrape off a few grains of magnesium into your tinder and ignite it by striking the ferrocerium. The sparks from the ferrocerium will ignite the magnesium, which will in turn ignite the tinder. 
It is also known in Europe as Auermetall after its inventor Baron Carl Auer von Welsbach. Three different Auermetalls were developed: The first was just iron and cerium, the second also included lanthanum to produce brighter sparks, and the third added other heavy metals.
In terms of composition, modern flint is derived from 75% mischmetal and about 20% iron. A variety of other components are added to modify the spark and processing characteristics. Most contemporary flints are hardened with 20% iron oxide and 2% magnesium oxide.
- Intermetallic - in the Baron von Welsbach's original alloy, 30% iron (ferrum) was added to purified cerium, hence the name "ferro-cerium". Iron reacts with rare earth metals to form hard intermetallic compounds similar to those in neodymium magnets; such magnets are also known to generate sparks quite easily when broken.
A modern ferrocerium firesteel product is composed of an alloy of rare earth metals called mischmetal (containing approximately 50% cerium, 25% lanthanum, and small amounts of praseodymium and neodymium), plus iron and a small amount of magnesium:
- Klaus Reinhardt and Herwig Winkler in "Cerium Mischmetal, Cerium Alloys, and Cerium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry 2000, Wiley-VCH, Weinheim. doi:10.1002/14356007.a06_139
- Cerium flint rod product description
- Jorgenson, John D.; Corathers, Lisa A.; Gambogi, Joseph; Kuck, Peter H.; Magyar, Michael J.; Papp, John F.; Shedd, Kim B. "Minerals Yearbook 2006: Ferroalloys". United States Geological Survey. Retrieved 2009-04-24.