The word 'chakra' is derived from the Sanskrit word meaning 'wheel'. If we were able to see chakras (as many seers and psychics, in fact, do) we would observe a wheel of energy continuously revolving or rotating. Each chakra rotates at a different speed. One of the reasons that many people fall ill is because their chakras become out of alignment, they are 'imbalanced' or there are blockages which restrict the free flow of the body's energy. There are seven major chakras and dozens of minor ones.
For simplicity I have listed the seven major chakras, they are as follows:-

The root chakra - first chakra
Location:The base of the spine. . This is where the kundalini is situated.
Gems and Minerals: Ruby, red jasper, garnet.
Colour: Red.
Attributes: It is a very important centre as it has so much effect upon the rest of the body. You may find you that you are able to release a great deal of the physical stress and tension of the nervous system by working on the base chakra with a quartz crystal. Grounding, good health, survival instincts, vitality, and sexuality (for men).
When Unbalanced you may experience: Violence, anger, constipation, survival fears. To Awaken and Balance: Spend some time each day sitting directly on the earth.

The sacral chakra - second chakra
Location: The second chakra is located within an area bounded by the spleen and sexual centre. The lower belly.
Gems and Minerals: Amber, citrine.
Colour: Orange.
Attributes: Creativity, sexual energy (for women), desire, and pleasure.
When Unbalanced you may experience: Sexual problems, jealousy, possessiveness, uterine or bladder problems, lower back pain. To Awaken and Balance: Sexual healing, try new ways of expressing yourself creatively, dance, move your hips, and practice yoga.

Solar plexus - third chakra
Location: The solar plexus (between the chest and the navel.)
Gems and Minerals: Gold, tiger's eye.
Colour: Yellow (like the sun.)
Attributes: There is often a great amount of physical energy and power within this chakra or emanating from it. This chakra is also the psychic store - house of mystical energy and is the energy centre used by materialisation mediums for producing ectoplasm and other psychic manifestations. The will, determination, assertion, personal power, hearty laughter.
When Unbalanced you may experience: Lack of will, overemphasis on power, anger, poor digestion, eating disorders, fear, and hate.
To Awaken and Balance: Rub your belly, become aware of the energy radiating from your solar plexus, and breathe using your diaphragm.

Heart chakra - fourth chakra
Location: The heart area in the centre of the chest.
Gems and Minerals: Emerald, malachite, green jade.
Colour: Green.
Attributes: You can use the heart chakra to help people suffering from emotional traumas and problems in their relationships. By using a piece of rose quartz you maybe able to help release their inner emotional tension and trauma. Unconditional love, forgiveness, compassion, group consciousness, peace, tolerance.
When Unbalanced you may experience: Anger, heart problems, rigidity, lack of love.
To Awaken and Balance: Serve others, love and take care of yourself. Breathe consciously. Watch tender movies that "tug at your heart strings."

Throat chakra - fifth chakra
Location: Throat area.
Gems and Minerals: Lapis Lazuli, sodalite, blue quartz.
Colour: Sky blue.
Attributes: Communication, expression, eloquence.
When Unbalanced you may experience: Difficulty communicating, emotions caught in the throat. When people suffer from headaches (perhaps migraine) and tension within the neck and shoulder muscles often the basic cause is that the throat chakra has become blocked To Awaken and Balance: Sing, chant, hum, breathe consciously.

Third eye - sixth chakra
Location: Between the eyebrows
Gems and Minerals: When helping people to develop their own spiritual intuition amethyst, sodalite, lapis lazuli or sugilite are ideal stones with which to work.
Colour: Indigo Blue.
Attributes: Intuition, imagination, visualisation, concentration.
Element: Light.
When Unbalanced you may experience:Headaches, poor eyesight, lack of concentration. To Awaken and Balance: Meditation, guided visualisation.

Crown chakra - seventh chakra
Location: The top of the head.
Gems and Minerals: Diamond, quartz crystal.
Colour: Violet.
Attributes: Inspiration, wisdom, cosmic consciousness, spirituality, oneness with all.
When Unbalanced you may experience: Depression, lack of grounding, lack of inspiration (because you're disconnected from your spiritual source.)
To Awaken and Balance: Meditation, guided visualisation, energy work. During any crystal healing session this chakra needs to be open. It is the chakra through which you obtain the highest understanding and the highest knowledge.

These chakras all play an extremely active role in all our crystal healing treatments. As already mentioned any 'imbalances' that exist within any chakra may have profound effects upon either our physical or physiological bodies. We are able to use our quartz crystals to re-balance all our chakric centres and once the chakra has been properly balanced then our body will gradually return to normality. To balance the chakras you can use the following technique. First lay down on your back. Then place two quartz crystals on the third eye chakra, points facing downwards. Two quartz crystals on the palm, points upwards; two quartz crystals on the breast area, points upwards; and two quartz crystals placed on the top of the thighs, point upwards. If you lay quietly on your back for about 15 minutes, the chakras will quickly re-align themselves.