Every time you purchase or are given a new Crystal you should cleanse and recharge it. This gets rid of any unwanted programs and negative energies that may still linger in the Crystal from previous owners or even from people who may have held it in the shop. You should try and cleanse the Crystals once a week or after using them for healing.
There are several methods to choose from but I find that these are the best.
Pendulum
Water & Salt
Smudging
Using Nature
Using other Crystals
I will go over these in the following paragraphs...
Use either a Clear Quartz, Rose Quartz or Amethyst Pendulum.
Place the Crystal to be cleansed in the centre and hold the pendulum above it...
Alow the Pendulum to circle the Crystal nine times, anti-clockwise. (this removes any negative energies held in the Crystal)
Then cleanse your Pendulum with cold water (again dip it nine times) and then shake it dry.
Then once again allow the Pendulum to circle the crystal nine times, this time in a clockwise motion...this charges the Crystal ready for use.
(This method is recommended in Cassandra Eason's book..."The Illustrated Directory Of Healing Crystals")
Normally I would just run a Crystal under a cold water tap to cleanse it but many Crystals would be damaged by this method. It is best to use your intuition.
I would recommend the two bowl method.
Get one large bowl and one small bowl...make sure the small bowl fits into the larger bowl and that it is big enough for your Crystal.
Place the small bowl inside the larger bowl and then pour cold water between the two bowls.
This can be left for a few minutes or a few hours depending on how often you have used the Crystal.
Some Crystals can also benefit from Salt...a small pinch of Sea Salt or Rock Salt can be added to the water for extra effect...works better on Crystals which come from or have been tumbled in the Sea.
I have tried this once and find that for some Crystals it is highly recommended!
You can use a Sage or Cedar wand (available in most shops) or incense sticks in Cedar, Sage or Pine (I use a Moldavite one as this is a also a Crystal and sometimes you can get Amber incense sticks too)
This would be the best method for cleansing several Crystals at once.
Place the Crystals to be cleansed in a circle and pass the wand or incense around the circle...alternatively you can pass a Crystal through the smoke to cleanse it.
This means you can charge the stone under certain weather conditions, during the day or during the night or even with plants and herbs.
A good method is the day/night cycle. Place your Crystal near a window during the day or night depending on your Crystal. Darker coloured Crystals (like Amethyst) prefer to be charged at night, under the stars or moon - whilst light or clear Crystals, like Quartz, would prefer to be charged by sunlight.
Some stones prefer different weather conditions...like rain, thunder and rainbows. A fine example of this is Labradorite...it has so many colours that it is best to place this Crystal in a window whenever you see a rainbow in the sky.
Another good method is plants, herbs and earth. Green stones like to be placed amongst the green leaves of a plant whilst brown stones like to be buried for 24 hours in a pot of earth. Also herbs are good too...use Lavender, Rosemary or Sage to cleanse your Crystals.
Go with the flow...choose your method by deciding what would be right for the Crystal...having a few books on Crystals will help you understand how Crystals are formed and which of the above methods would suit them.
You will need an Amethyst or Quartz structure to do this....
Usually a matrix or natural formation of some kind...
You can just lay the Crystal to be recharged on top of the formation or place it (if it is small enough) in a dark coloured silk bag with the piece of Amethyst/Quartz in a dark place for at least a day.
This recharges and heals the Crystal slowly.