Yes I do it all the time. Remember that granite is cooler than room temperature. After tempering I use a paint brush to coat a small section on the granite then have my pastry scraper ready to create cigarettes, and tubes and cones of all shapes and sizes.
You gotta be quick or else the chocolate will harden and you won't budge it without breaking. Experiment....
No experience with granite, though I have recently started experimenting with baking, using puff pastry, ect; I have been using a marble board with good results. Had thought about chilling it a few times but I don't want to fight with the fridge or freezer trying to find a spot. Isn't granite somewhat rough/porous? I haven't seen the material in a long time now that I think about it.
Sorry, by experience with granite, I meant as a work surface for chocolate decor. I have seen many people work on metal counters, marble counters but no one on granite. It seems like it would work fine but I was curious.