I've recently found a great place to pick up broken slate in all colours
virtually free. (The guys just want a couple of bottles of beer.)
Considering that the store wants $5 for one broken slate tile (grey) this
seems like a deal to me. My question is: Is slate, slate no matter what the
colour? Does one have to watch out for glazes etc.? Any info out there?

in Vancouver, grey, overcast and light rain -- but going to clear! :)