There are many methods of cleansing your crystals these include:
Sea salt is the most traditional purifying agent in psychic work and healing. It dispels any sort of un-ease and negativity, and is a physical and psychic disinfectant. I feel it is the most accepted and probably the most powerful method of clearing crystals and stones. I highly recommend it for the initial cleansing of a new healing stone and for any time a stone is overloaded with negative energy. Salt can be mixed with water or used dry. To use salt water, mix a tablespoon of sea salt in a glass or ceramic cup of cold water. Do not use plastic or metal containers. Place the stones in the solution and allow soaking overnight. To use dry salt, place the sea salt in a glass or non-plastic container and bury the crystals with the points facing downward into the salt. Again, leave overnight. Sometimes a stone may take longer to clear, especially if it has been used in a deep, intense healing. If this is the case, leave another day or two in the sea salt. When clearing gemstone necklaces it is best to use the dry sea salt method. Be sure to use sea salt only, table salt contains aluminum and other chemicals. For those who live by the ocean, salt water can be brought from the beach in a jar, or gently wash them directly in the ocean.
Moonlight is another way of clearing your gemstones. Simply place outside from the Full to the New Moon. Waning Moons are good times to clear crystals, to dispel old energies, but any time works. The amount of time used varies with the sensitivity of the healer and the amount of material from which the stone needs cleansing. Try hanging your gemstone necklaces in a tree where the moonlight can cleanse them. (I personally do not recommend ever placing your crystals and gemstones in the sunlight, many stones tend to fade their colors in the sun. Also internal fractures may cause your stone to crack or break if placed in the sun.)
Other Methods That Work Well
Burying your crystal in a cupful of dried herbs will also clear it. Suggested herbs for this are rose petals, sage, frankincense, myrrh, and sandalwood. You can usually find these at low cost at many co-ops or herb stores. This is a gentle way to clear crystals, and a pleasant way, but it does take longer than sea salt. Crystals may also be buried into the Earth. This is especially helpful when you feel deep cleansing is needed. Outdoors, simply dig a hole the size of your crystal into the Earth, place your crystal again point down, and cover with soil. The amount of time needed is personal choice. Be sure to place a Popsicle stick or some other marker to insure you fine your stone again!!! For apartment dwellers, use a flower pot to bury your stone in. A quick way to cleanse your healing stones is to smudge them with burning cedar or sage. Smudging is an excellent way to make sure your stones are purified. Simply hold the burning sage or cedar stick while passing your stone through the smoke. I usually do this a couple times to ensure cleansing. I also like to cleanse my stones by smudging after every healing.
Finally, if you are in a hurry and feel that your crystal needs to be cleared, you can easily run them under cool tap water. Make sure the points are facing down the drain to run the negative energy right down the sink!!! NEVER USE HOT WATER, THIS WILL FRACTURE OR BREAK YOUR CRYSTALS. Visualize the crystal as sparkly, tingly, cold, and belonging to the healer. Make sure you clean your crystals on a regular basis and you will have a great crystal experience every-time!