Practitioners repeatedly describe crystals as "tools" that enable people to heal themselves, know themselves, more effectively influence their lives.

While a few crystal experts suggest the scientific community is discovering new evidence about crystal energy, most admit there is no scientific basis. Metaphysics means beyond physics, they say. And that means crystals power, at least so far, defies scientific explanation. No practioners interviewed and none of the crystal books surveyed recommended substituting crystal exercises for conventional medical treatment.

Some of the claims made for crystals:

The process of selecting a crystal is considered a mutual decision by most crystal power aficionados. "You not only choose the crystal -- the crystal chooses you," writes Serenity Peterson, a Nashville, Tenn., crystal retailer and author of Crystal Visioning (Interdimensional Publishing, $8.95). " ... you have heard the song of the crystals calling your name."

Crystals can store "thought-forms." Dael Walker, author of The Crystal Book, believes that researchers who have investigated ancient crystal skulls found in Central America have experienced "visions of all ages ... " Walker believes that before the end of this century researchers will find and decipher crystals that are storing 200,000 years of knowledge as "three-dimensional thought holograms."

Carrying a crystal or wearing a crystal pendant provides psychic protection against negative thoughts and imbalanced emotions.

Crystals, some practitioners claim, are like metaphysical telephones that connect to this and other worlds. Uma Silbey recommends using a large crystal -- "sometimes called a generator crystal" -- to energize yourself before "channeling information from more subtle planes."

For better gas mileage (up to 20 percent increase), Dael Walker recommends attaching a 3- to 4-inch diameter clear cluster of crystals that has been correctly "charged" to the gas line near the carburetor of your automobile. "I just tell people, 'Try it yourself,' " says Walker. "It goes beyond normal physics. The wave form changes the vibration ... and that affects the molecular structure of the gasoline. I think that's what happens, but I don't know how the heck you are going to prove it."

Using visualization techniques similar to those that scientifically have shown some success in combating cancer and other diseases, most crystal practitioners believe the unconscious mind can be "programmed" with the help of crystals to affect conscious life -- from attracting wealth to attracting love. Paul R. Caruso, who conducts crystal locally, says rose quartz has the metaphysical properties to attract and emit love.

Methods and exercises claimed to assist in healing vary from holding a crystal in the left hand and visualizing a disease-free body to meditating with specific gems and stones placed at "power points" on the body.