Crystals need to be cleansed for many reasons. Whenever you work with crystals, whether it be for yourself or with others, the crystals absorb the energy from you, or other people, or from the environment they are in. Crystals work best when they are cleansed because overtime they absorb and accumulate energy from the environment around them. You'll also be able to see when the crystals need cleaning as they will become dusty, and will lose their sparkle, luster, and even their color. Once crystals pick up energy from another place they will eventually need to release it sooner or later, so you want to be sure and cleanse the crystals properly so you aren't picking up energy that comes from somewhere else. A dusty crystal will not work as effectively as it blocks the light which reduces the number of photons that the crystal focuses on. You can also remove dust with a soft brush such as a makeup or small paintbrush.
Earth. Another way to cleanse your crystals is by burying the crystal in the Earth. Bury the crystal in the Earth and leave the crystal there for one to two weeks or for a full moon cycle. You can bury the crystal when the moon is full and remove it when it is the new moon.
Incense. Use frankincense, sage, or sandalwood smoke to waft over your crystal.
Moonlight. Leave your crystals out during the full moon when the moon is at its brightest. Bathe your crystals under the moonlight to help restore them to their brightest form.
Sage. A sage smudge stick is an excellent crystal cleaner. You just want to make sure that you have something underneath to catch any falling embers, an abalone seashell works well. Light the smudge stick and using the smoke, waft the smoke over your crystals.
Sound. Sound is an easy way to cleanse your crystals of any unwanted energy. You can use music, Tingsha Tibetan cymbals, Tibetan bowls, chanting, or drumming. Tingha Tibetan cymbals shake the crystal on a molecular level with the vibration which shakes off the unwanted energy.
Sunlight. The sun burns off old energy and refills the crystal with light and vibrancy. Leave your crystals in the sunlight, but be sure to not leave Quartz crystal in direct sunlight as it will focus the sun's rays and could start a fire. Some crystals such as Amethyst may fade if left in direct sunlight for an extended period.
Water. One way to cleanse your crystals is by soaking them in distilled water and a bit of sea salt (1/2 teaspoon) and letting them soak for 7 days. This will help to purify the crystals and get them ready for other uses. Some crystals will dissolve or rust (if iron is present in the crystals) in this mixture, so you will want to research this first. A quick and easy way to cleanse your crystals is simply by running them underwater, but you want to be sure and not do this with water-soluble crystals. A natural spring, stream, or river is the ideal source, but tap water also works well. To cleanse in running water, hold the crystal under the flow of water for one or two minutes. You can cleanse the crystal longer if it hasn't been cleaned in a while or the crystal has been working overtime. Running water is one of the easiest ways to cleanse your crystals.
Whatever way you choose to cleanse your crystals you will want to make sure and do so with a clear mind and focus on what you are doing. You want to be sure and concentrate on your intent and take your time as it is not something you want to rush.