Popular with military and survival folks, and commonly available at any gear shop, magnesium/ferrocerium fire-starters are a standard outdoors tool.
They are cheap, reliable, and waterproof, and they are an alternative to matches or a Bic. Many outdoorsmen keep magnesium in their kit for “just in case” situations.
Scrape off a few shavings from the block onto dry grass or kindling — that’s your fuel. Turn the block around and strike the ferrocerium metal with the blade to shoot out sparks and light the metal tailings.
Once ignited with a spark, magnesium burns rapidly at a whopping 5,610 degrees Fahrenheit. Your leaves and grass will catch a flame, then you add twigs, sticks, and larger logs as the fire grows.
For this test we used the $5 Coghlans 7870, one of many similar products available. See the video tutorial and instructions below.
While the magnesium/ferrocerium method works, it’s hardly foolproof. Practice a few times in a controlled, safe situation before relying on this system in the woods.