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Ultimately, they are used to cleanse the person from bad or negative energy believed to cause an illness. Clearing out the bad spiritual energy alleviates the physical ailment. Crystals are used for physical, mental, emotional and spiritual healing. Not only do people visit "crystal healers"; there are also professional nurses are being trained to use crystals for their patients.
Additionally, crystals can be worn, placed next to a person's bed as they sleep, and in some cases placed around a person's bath.
The originator of crystal healing is unknown. However, this practice has been around for centuries. People have used amulets, magical stones, and gems all throughout history (though mainly in the eastern cultures).
Crystals and gemstones have vibration frequencies which are perhaps shape induced, providing an interconnection between the earth's energy field and the magnetic energy field of the individual. The crystal is used to amplify, or realign, human 'psychic' or cosmic energy by directing vibration energy. To maintain the crystal, it is placed in salt water or covered with table salt. Maintaining the crystal helps keeps it clean from "environmental imbalance."