I always wanted to try this, and the talented Amy Lou Stein taught me how, while we were in Maine for Fiber College last week. I can’t stop.
If you are not fortunate enough to have her as your friend, check out this link How to Crochet a Rock and find amazing tutorials and art to inspire.

PS Amy Lou opened CraftWork in Somerville MA in October 2015! She teaches crochet there, even on rocks, from time to time--check her out.