Ferrocerium

It takes its name from its two primary components: iron (from Latin: ferrum), and the rare-earth element cerium, which is the most prevalent of the lanthanides in the mixture.

Except for the extra iron and magnesium oxides added to harden it, the mixture is approximately the combination found naturally in tailings from thorium mining, which Auer von Welsbach was investigating.

[4] In Auer von Welsbach's first alloy, 30% iron (ferrum) was added to purified cerium, hence the name "ferro-cerium".

Two subsequent Auermetalls were developed: the second also included lanthanum to produce brighter sparks, and the third added other heavy metals.

A modern ferrocerium firesteel product is composed of an alloy of rare-earth metals called mischmetal, containing approximately 20.8% iron, 41.8% cerium, about 4.4% each of praseodymium, neodymium, and magnesium, plus 24.2% lanthanum.