More recently the term 'firesteel' has become synonymous with so called 'artificial flints' which are metal rods of varying size composed of ferrocerium, an alloy of iron and mischmetal (itself an alloy primarily of cerium that will generate sparks when struck). Iron is added to improve the strength of the rods. Small shavings are torn off the rod with either a supplied metal scraper, a piece of hacksaw blade, or, commonly, the back of a knife ground at a suitable angle. These shavings then ignite at high temperatures, and they are much more effective than their historical equivalent.
While it takes practice and properly prepared tinder to create a sustained fire, the modern firesteel is considered by survival instructors and serious outdoorspeople to be one of the most reliable ways of making fire in severe conditions. The sparks produced by these products are extremely hot, 3000 °C (5500 °F), and easily light toilet paper or small pieces of wood or commercial tinder products.
Modern firesteels are widely available in outdoor shops.
Traditionally a flint and steel were used; however, the flint was not the important part. With a proper striker, you can get sparks using any hard, non-porous rock that has a sharp edge, even petrified wood. The spark comes from chipping small pieces of steel off the striker; finely divided metals ignite immediately in air, with steel burning at yellow-white heat.
Charpaper can be used as an intermediate step between the striking and the tinder.