Some Practical Uses
Many years ago I remember reading a book by Soozi Holbeche and she recommended placing a quartz in to a jug of water and leaving it to sit overnight. Drinking the crystal infused water is said to cleanse your aura of negativity from the inside out which will leave you feeling more positive and vibrant. I followed her advice and found it did indeed make me feel more energised.
A good sized chunk of a quartz cluster strategically placed in a busy room will absorb any conflicting energies that may arise. Clear quartz will often go cloudy over time, and it is said that this occurs because of the negativity it has absorbed from its surroundings.
Placed next to other crystals ~ it will cleanse the negative and amplify the positive. Use as a booster for stubborn spiritual issues that need more earth-force.
Carry quartz in your pocket if you want to keep your aura clear when dealing with people who are not on the same wavelength as you. Or if you like, you could purchase a pendant to wear but make sure the stone has been set properly if you want it to work at its best. Ideally it needs to be held around the middle and not have the negative end blocked off completely by whatever the jeweller has used to attach the chain. The crystal will still push out the positive energy but won't be able to absorb negative. This is of course perfectly fine if it suits the purpose you're using it for.
And Finally...
It's not such a good idea to put clear quartz under your pillow if you're sensitive to the vibrations because it's an incredibly active energy ~ you wont be able to sleep. Sometimes you will see rainbows that have formed inside the crystal and the mystics and healers believe this is a particularly strong sign that the stone is to be used in healing. They appear at a point of damage within the crystal and show the crystal has been able to heal itself from the trauma. Rainbows symbolically represent hope of recovery and are always a good sign wherever you see them.