Before you use your crystals they should be cleansed so that they dont hold any negative energies from the person who previously handled them. This can be done in different ways.

1.) You can put your crystals in a bag with clear quartz or carnelian over night. These crystals can cleanse other crystals.

2.) You can hold the crystals under running water, or immerse them in salt water while visualizing all the negativity being washed off of them.

3.)You can leave them in salt overnight.

4.) You can pass them through the light of a candle or visualize a white light around them, energizing them.

Hi,

I really don't think it is a good idea to tell people to use salt to cleanse and especially not to leave crystals in it overnight as many crystals will end up damaged and lose their patina as well as become friable.  Salt is a much more useful cleansing and protecting element when used in witchcraft and nowhere near crystals.
Clear Quartz absorbs energy more than most other crystals so this isn't a good cleansing stone either. Using a bew of Amethyst does help though


Cassie

You definately want to keep into consideration which kind of crystal it is and what is the best of way of cleansing them.

Crystals should not be held under running water or placed in water if they are friable or jointed, and if cleansing with the sun be sure it is not a stone that fades in sunlight.

Salt and water (or salt water) is a very effective way of cleansing your crystals, but be careful which crystals you put in the salt. You should avoid this method of cleaning for crystals that have water content, are porous, or ones that contain metal.

If you are unsure if the crystals you are using can be cleansed with salt or water then its probably best to choose a different method of cleansing them, like visualization.