Crystal healing is a pseudoscientific alternative medicine technique that uses semiprecious stones and crystals such as quartz, amethyst or opals. Adherents of the technique claim that these have healing powers, although there is no scientific basis for this claim.
In one method, the practitioner places crystals on different parts of the body, often corresponding to chakras; or else the practitioner places crystals around the body in an attempt to construct an energy grid, which is purported to surround the client with healing energy. Despite this, scientific investigations have not validated claims that chakras or energy grids actually exist, nor is there any evidence that crystal healing has any greater effect upon the body than any other placebo; for these reasons it is a pseudoscience.
Precious stones have been thought of as objects that can aid in healing by a variety of cultures. The Hopi Native Americans of Arizona use quartz crystals for divination, including locating sources of pain or disease in the body. The Hopi also traditionally use crystals for other forms of divination, as prisms to direct sunlight towards medicine bowls, and in other forms of ritual, such as imbuing the strength and toughness of the crystal into one's heart. Both Pliny the Elder and Galen claimed that certain crystals had medicinal properties. In Europe, the belief in the healing powers of crystals (and in particular crystal amulets) persisted in to the Middle Ages. 
In the English speaking world, crystal healing is heavily associated with the New Age spiritual movement: "the middle-class New Age healing activity par excellence". In contrast with other forms of complementary and alternative medicine (CAM), participants in crystal healing view the practice as "individuated", i.e., dependent on extreme personalization and creative expression. Practitioners of crystal healing purport that certain physical properties—e.g., shape, color, and markings—determine the ailments that a stone can heal; lists of such links are published in commonly distributed texts. Paradoxically, practitioners also "hold the view that crystals have no intrinsic qualities but that, instead, their quality changes according to both" participants. After selecting the stones by color or their believed metaphysical qualities, they place them on parts of the body. Color selection and placement of stones are done according to concepts of grounding, chakras, or energy grids.
There is no peer-reviewed scientific evidence that crystal healing has any effect; it is considered a pseudoscience. Alleged successes of crystal healing can be attributed to the placebo effect. Furthermore, there is no scientific basis for the concepts of chakras, being "blocked", energy grids requiring grounding, or other such terms; they are widely understood to be nothing more than terms used by adherents to lend credibility to their practices. Energy, as a scientific term, is a very well-defined concept that is readily measurable and bears little resemblance to the esoteric concept of energy used by proponents of crystal healing.
In 1999, researchers French and Williams conducted a study to investigate the power of crystals compared with a placebo. Eighty volunteers were asked to meditate with either a quartz crystal, or a placebo stone which was indistinguishable from quartz. Many of the participants reported feeling typical "crystal effects"; however, this was irrespective of whether the crystals were real or placebo. In 2001 Christopher French, head of the anomalistic psychology research unit at the University of London and colleagues from Goldsmiths College outlined their study of crystal healing at the British Psychological Society Centenary Annual Conference, concluding "There is no evidence that crystal healing works over and above a placebo effect.”
Crystal healing techniques are also practiced on animals, although some veterinary organizations, such as the British Veterinary Association, have warned that these methods are not scientifically proven and state that people should seek the advice of a vet before using alternative techniques.
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