I would think of it more as an igniter, like a match, than a firestarter. I've used the magnesium block with the shaver and sparker to light a fire, but always by shaving the magnesium into a tinder
like tissue paper or some kind of tinder to catch the burning magnesium and hold the fire. Of course
I ended up doing it with cattails and dryer lint, and then realized I didn't really need the magnesium - so I don't bother with such things <img src="/forums/images/graemlins/wink.gif" alt="" />