What makes these things "strike anywhere"? Conventional safety matches contain sulfur (that's the stuff that burns), glass powder (which provides friction), an oxidizing agent (typically potassium chlorate), and some sort of binder to hold all this chemical goodness together. The striking surface on the box or book of matches contains an abrasive substance, usually sand or powdered glass, and red phosphorus.
Fascinating, Poindexter. How does it all work? When you strike the safety match against the matchbook, the friction from all that glass powder creates enough heat to turn some of the red phosphorus into white phosphorus. As you may know, that's some seriously nasty shizit which ignites on contact with air. This small flame, in turn, ignites the sulfur in the match head, with the oxygen released from the potassium chlorate feeding the flame. This is why matches flare up when you first strike them, then settle down to a smaller flame.
Great, but I wanted to know about strike anywhere matches... I'm getting to that. That white tip1 on strike anywhere matches contains phosphorus, usually sulphide P4S3, which eliminates the need for the phosphorus in the striker. This is why you can strike them on almost any rough surface; rocks, a zipper, your teeth, or even very rough beard stubble (though that takes a volatile match with a lot of phosphorus.)
Oh yeah... These things are illegal in many states because of the obvious fire hazard, but many online retailers sell them if one has some desperate fire-starting needs that can't be satisfied otherwise. Also Sasha Gabba Hey! informs me that they are nearly impossible to get in Australia, but were not always so.
Citing my sources:
This has been a content rescue of a node that desperately needed it.
1. For what it's worth, strike anywhere matches are apparently red in the UK. Thanks to Oolong for this one.
Roninspoon sez: Illegal? Really? I don't think I knew that. When I was a kid, we used to cram these in the barrel of bb guns and shoot them at each other. When they struck the ground, wall and sometimes us, they would light and look real cool. I'm surprised we never burnt anything down.