Pyrophoric iron

(Chem.) finely reduced iron, which ignites spontaneously on contact with air.

See also: Pyrophoric

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in periodicals archive ?
Gregite ([Fe.sub.3] Iron Sulfide Corrosion Products: [S.sub.4]) Pyrite (Fe[S.sub.2]) (i) Pyrophoric iron sulfide Marcasite (Fe[S.sub.2]) (pyrrhotite-FeS) results from Mackinawite (Fe[S.sub.0.9]) the corrosive action of sulfur Pyrrhotite ([Fe.sub.7] or sulfur compounds [S.sub.8]) ([H.sub.2]S) on the iron (steel) and moisture.
However, note that the aroma is coming not from the flint, which is acting purely as an inert anvil, but from the burning particles of pyrophoric iron. (Modern firearms and lighters, incidentally, employ "flints" made of a synthetic alloy of cerium and iron.) The smell of a struck flint or of gun-flint is an illusion.