In reply to Keelan McNulty:
I'm not sure what control vinyl is but assuming you're actually playing music from the disks they won't be out accumulating dust for long and you can always put the covers down on the decks when you're not actually mixing. Chalk is soft, it's not likely to harm your needles. It's more likely to cause problems in an optical reader like a CD player or something with a complex cooling system like a laptop.
jk