The perfect pocket guide to identifying rocks for beginners RSPB What's That Rock? is ideal if you struggle with how to tell the difference between granite and marble or limestone and sandstone. It's the perfect identification guide for beginners but also a handy field guide for the more seasoned nature lover. Featuring over 150 rocks, overviews of rock types show you what to look for where and similar rocks are shown side by side for quick comparison and identification so you can tell rock types apart. Become an expert rock-spotter in no time with RSPB What's That Rock?