Somehow I added "look up how flint and steel actually creates sparks" to my todo list in the past year. Now I know. I knew the flint wasn't actually that important and other stones could do it (or a grinder.) It turns out that the only "magic" is breaking off small enough particles of iron. The iron rapidly oxidizes when air hits it. If the new particle is small enough, the heat from the oxidation is enough to ignite tinder. Chemistry at work.
(Photo by Merriwether, who's first camping trip with his kids is about how I think most of our vacations would go if we didn't live right next to Disney World.)