Percussion fire production.
A link, spark or tinderbox is a piece of iron with a high carbon content or
steel alloy from which sparks are caused to fly by striking it against a flint
stone or similar rock.
In primitive times a percussion link was used to start a fire. Before the
discovery of steel, different varieties of pyrite or marcasite were used, along
with flint and other stones, to produce high-temperature sparks by striking or
friction that were used to start a fire.
From the Iron Age until the invention of friction matches, the usual way to
start a fire was to strike a piece of steel against a piece of flint.