Each stone has a signature vibration which it emits constantly like the quartz crystal in your watch.  The frequencies are so predictable that aircraft use them in their guidance systems.

Our body has a vibration as well which is not as consistant. When you are feeling angry, powerless, fearful or just out of sorts the correct stone will bring you back into balance through a process called resonance. This is science - not magick.

Whether you carry them in your pocket, place on your desk at work, or under your pillow for restful sleep, crystals can return your body to its natural frequency & balance.

If you are purchasing a book to learn more about the specific properties of each stone, I encourage you to buy one that has been written in North America. I have found that traditional usages in other parts of the world vary greatly. And as always simply use your intutition.