I've used several clay magic blue clay bars (seen below, yes I used their lube) and every one of them were either hard and very hard to work with or fell apart. I tried the clay again with the same results. I was not impressed so no more clay magic for me. I even bought a pack in Florida and still the same.
Hopefully they will do something about this clay because right now you won't see me buying any. With my experiences there are many superior clays available which may cost a little more but you get what you pay for.