Crystals can be very powerful and are very sensitive. Crystals, like all things, have an energy field - aura - and their different energies can be used to balance/enhance our own body's energies. As with many natural therapies, crystals have been used as a healing aid for centuries.
Crystal energy, as colour energy, can help to awaken our awareness, not just of the physical imbalance / dis-ease, but awareness of the psychological, spiritual and emotional aspects of ourselves.Some crystals suit some people better or in different ways than others, but this simply emphasizes our uniqueness and our different needs. As with many forms of healing, we take what we need. The choice of a crystal can be simply your body knowing what it needs without the 'interference' of the intellect. This is often apparent when someone who has no experience in crystal healing will instinctively choose a crystal which happens to be the very type which their body requires.
There are many ways of using crystals and they can be obtained in different forms; the natural unpolished pieces, tumbled stones, cut points, essences, and pieces of jewellery set with crystals. Essences are similar, in a way, to solarized water in that the crystal is placed in water for a period of time and the specific energy of that crystal is transmitted to the water which is subsequently used for drinking or bathing.
There is no right and wrong with crystals - trust your intuition.