They're pretty hardy, just make sure you find a healthy specimen to start with. I tell beginners to stay away from the smaller "chips" I see for sale, get decent looking "head" of acan instead. Even if it costs a bit more.
Last frag swap I was at I saw a vendor with what looked like 20 1/2" squares of acan glued to frag plugs. Obviously all from the same puzzle, I couldn't help but wonder if he thought of cutting in quarters to get a better sale. Then again, he was selling them, so who am I to judge?
Jeff