This is just a W.A.G., there may be a more scientific answer. My guess is that dust and other particules in the air settle on the head unnoticed until repeated strikes of the sticks in more or less the same location drive the dirt into the head and the accumulation eventually becomes visable. What do ya think?

Your sticks are what make the black marks, but its from playing your cymbals with them & then it transfers the tarnish, etc, to the drumhead hence making the marks.

Yepper............

And I thought it was from my really, really fast stick-work, burning the skin. (Maybe that doesn't sound so good). Anyone ever test this with new sticks/head and not touching the cymbals?

L-D is 100% correct!! look at after you've played in a smoke filled room at your stick tips and your heads! stick funk!!!

I don't have the issues with smoke anymore......Mssachusetts and New Hampshire have banned smoking inside the clubs now. Instead you have to walk through a mushroom cloud of cigarette smoke by the entrance from all the smokers outside the club that are smoking. DOH

Ahhhh! Very good answer!

Indeed! Good answer!

So, then, say....an orchestral snare drummer or a marching snare drummer who never hits a cymbal with his sticks will not suffer these dirty black marks on their coated drumheads then, right?

I'm picking up new tom and snare heads, so I will do an experiment and see if I can offer some test-results for this phenomenon. All test heads will be coated Evans G2's and the sticks will be Vic Firth 5A CLassic wood tip. FYI: My current clear hydraulic Evans heads have no black marks on them, just smudges.