They all seem to have CRYSTAL in the name somewhere...they are the ones that look like whitish/translucent beads. Not clay/clumping type or the organic variety, eg:
http://www.homeshop.com.au/images/p/52/00210752.jpg
Might pay to remove the blue ones (volatiles?) and bake at 150C for an hr before first use....same method can be used to re-activate.
You can also get small amounts for nothing at all if you talk nicely to your local shoe shop....