Its like the sandal wood… you cannot make powder out of it… so what is the next best thing is to get a stone, i think you can do it using pumice stone as well,…you know how they make sandal paste right??
if you dont… then here goes… wet the stone, put like 2 drops of extra water on the stone,dip the turmeric in water, then start rubbing it on the stone, you will get paste kind… be careful not to put excess water or else you wont be able to apply it..
hope that helps…