If you are into working with crystals and gemstones then Scott Cunningham wrote an excellent book called 'Crystal, Gem and Metal Magic'.
It gives a comprehensive list of all commonly known crystals, gems and metals, and some really uncommon ones too. (Though new ones have been found or named since then and are obviously not there.)

Along with some of their history, magical and medicinal uses, and any replacements you can use if you don't happen to have that particular stone. It also gives some correspondences, planets, colours, gods etc. And also has full colour pictures, but unfortunately only of some of the contents.
I found it a really excellent book, but having borrowed it from a friend I had to return it and now i am without a copy. I love gemstones and jewellry and really like knowing what to wear for luck, for money and for a good night's sleep, among many other things.

I'll keep a look out for that 'Good Magic' book Darkness. It sounds like just my kind of book. For formal magic I am a beginner, so I could use a book that takes you right from the start and tells you everything from basic tools. I need all the help I can get.

Edited to say:
Thanks to Moon for starting the crystal and gem magic section. I now it wasn't just for me, but I'm going to find it really useful anyway so thanks.

(And to take the extra 'ed' out of borrowed.)