Information about chalk sticking to blackboard

[whyme1010]

So chalk nowadays is made up of calcium sulfate rather than calcium carbonate. I want to know if there exists any data on spectral lines of calcium sulfate. If not, does combining the spectral lines of calcium sulfur, and oxygen create the spectral lines of the original molecule?

Why does chalk stick to blackboard? The chalk fills in the tiny gaps in whatever board you may be using, but I'm interested in how this solid-solid adhesion works.

 

[nowhat]

I suppose it is due to electrostatic force. When writing on the blackboard, there is charge induced by friction on the chalk powder, thereby sticking to the metallic blackboard.

But this is just a conjecture. Maybe you can (dis)prove it by experiments using a Van de Graaff generator?