I like to have natural elements in my living space - real wood, live plants, real stones and crystals.  In addition to being colorful and interesting accents, crystals can bring an added benefit of changing the energy in your room.  Placing crystals around the room is helpful in absorbing or transmuting energies.  A piece of smoky quartz or black obsidian will absorb negative energy.  Amber and bloodstone cleanse and transmute energies.  Black tourmaline, jet, fluorite and black jade return energies that have been directed towards you back to their source - as does a mirror placed facing the direction from which psychic attack emanates.  Rose quartz and amethyst attract protective, loving energies.  Turquoise clears environmental pollutants and malachite is helpful if you live near a nuclear power station.  Source:  Thorsons Way of Psychic Protection by Judy Hall.