Sugar Crystals were a bit like sherbet dip-dabs (without the dipper), but you could only get it in the proper sweet shops, as you bought it by the quarter. They came in different flavours and colours and had a very slight sour tang. You dipped your finger into the white paper bag, the bag would eventialy get a bit soggy and your finger was stained in whatever colour you'd had, for days after! Pure tooth rot in a bag, really. No wonder the dentists did so many fillings in the 70s!