[Eurytus]

For anyone who wants more information on the geography of Middle Earth (one of the aspects that most interests me) might I recommend Karen Wynn Fonstad's "The Atlas of Middle Earth".
This is a fantastic book and unlike some others, seems to be pretty damn accurate. Indeed it gets really into the details of what rock types different geological formations might be comprised of and all sorts.
Really, really good book. Best Tolkien book I have bought that has not been written by the man himself and I include all of Christopher Tolkien's stuff (with the exception of the Silmarillion, Lost Tales and Unfinished Tales in that).