Ferrocerium is a synthetic pyrophoric alloy of mischmetal hardened by blending in oxides of iron and/or magnesium. When struck with a harder material, friction produces hot fragments that oxidize rapidly when exposed to the oxygen in the air, producing sparks that can reach temperatures of 3,315 °C (6,000 °F). The effect is due to the remarkably low ignition temperature of cerium, between 150 and 180 °C.

Mischmetal (from German: Mischmetall – "mixed metal") is an alloy of rare-earth elements. It is also called cerium mischmetal, or rare-earth mischmetal. A typical composition includes approximately 55% cerium, 25% lanthanum, and 15~18% neodymium, with traces of other rare earth metals; it contains 95% lanthanides and 5% iron. Its most common use is in the pyrophoric ferrocerium "flint" ignition device of many lighters and torches, although an alloy of only rare-earth elements would be too soft to give good sparks. For this purpose, it is blended with iron oxide and magnesium oxide to form a harder material known as ferrocerium. In chemical formulae it is commonly abbreviated as Mm, e.g. MmNi5.