The sparks are actually coming from the steel and not the stone. Flint is just a very hard and sharp stone that can make tiny bits of steel fly off, heated from the sheer friction.
A different stone that is hard and sharp enough would have the same effect, like pyrite also known as fool's gold. A different metal with, i believe, not enough carbon in it would not work. Thank you for coming to my TED talk.
You called it, like clockwork