Oh, rock salt is dead useful! It's great for use in painting, and I also use it as a base under candles (in a glass) so that the candle doesn't harm whatever surface it's sitting on. In Feng Shui they say to place a small pot of it in the corner of a room to absorb negative energy. ;~) So I like to think that my little glasses of rock salt and tealight candles are performing a double function! Heh!