Natural quartz and amethyst are both piezoelectric, meaning they have a positive and negative polarity and can emit electromagnetic energy.  These highly sensitive stones can be used in dowsing to identify and neutralize negative earth energies or geopathic stress, which can cause lethargy and general tiredness.  The human body adapts to normal earth energies (or radiation waves) that come up through the ground.  Geopathic stress occurs when these energies become distorted.  To find if you have any negative energy in your living room, take your natural quartz pendulum and ask it to show you "yes" and to show you "no." ( Wait for the pendulum to move in response to your question.)  Then walk around the room and stop at different points and ask the pendulum "Are there any negative earth energies here that are affecting my health?"  Write down any areas where it swings positively.  Place two large pieces of amethyst in the affected areas or place several small pieces under the carpet if possible, asking for their help in neutralizing the negative vibrations that are adversely affecting your health.  You could also use rose quartz to smooth away harsh energy, smoky quartz to gently neutralize unhealthy earth vibrations or obsidian to create a shield against negative energy.  Source:  Crystal Energy by Mary Lambert.