Ferrocerium
Ferrocerium is a synthetic pyrophoric alloy made out of mischmetal (rare earth metals) and is mostly composed of cerium, lanthanum, iron, and a small amount (~4.4% each) of praseodymium, neodymium, and magnesium. Ferrocerium is mainly utilized in starting fires, as, when struck with something harder than itself, it produces hot fragments that rapidly oxidize and produce incredibly hot sparks that are upwards of 3,350°C (6,000°F).
Uses
Ferrocerium is almost exclusively used in the starting of fire, and in order to light a fire using ferrocerium, all you need is a solid piece of ferrocerium, and a striker (knife, axe, spear, etc.). It must be noted that the striker must be harder than ferrocerium in order to create sparks necessary in starting a fire.
Safety Disclaimer
Ferrocerium sparks can be incredibly hot and can cause burns if coming into contact with skin or external (and internal) organs whatsoever. Make sure to always handle both the striker and the ferrocerium with caution in mind.