Charging

The intensity of radiation from a crystal is connected with the absorbed energy, so its healing effect can be increased and fortified through targeted charging. The most gentle method consist of laying the stone in sunlight at sunrise and sunset. The time during which we can dare to look almost into the sun without damage to our eyes is when the sun possesses a charging quality.

Stones may be charged immediately before using it for a treatment, by holding it in your hand or near a radiator. This too will intensify the effect. In most cases charging is not necessary as the stone will be charged, warmed up and stimulated by body contact, but it does take a little longer and it is less pleasant in winter to have cold stones placed on the body.

Discharging

Crystals become statically charged when heated or when they come into direct contact with the body. The most extreme example is Amber, which may become quite hot in a few minutes.

Static charge can be discharged under running water (not recommended for all minerals).
Placing the stones in the midday sun for a few hours is another way to discharge them (not recommended for all minerals).
Healing stones can also be placed in a bowl of hematite. Hematite does not need any cleansing or clearing of its own. (This is my prefered method of discharging crystals, stones and minerals as it is safe and it will not cuase any damage to the stones)

Cleansing

Any information a crystal received from direct contact with a person's aura or physical body will remain stored even after the stone has been discharged. In order to completely wipe stored information, a more intense action is required.

Some crystals* can be placed in coarse sea salt. Salt needs more careful handling. Direct contact with salt may produce chemical reactions with some crystals, making the stone lose its polished finish or change colour. If you want to go the salt route I recommend laying the crystal in a small glass dish that is embedded in a larger glass dish full of salt. The energy cleansing process is still maintained, but the stone will not be damaged by the salt.
Another method is to place stones on an Amethyst druse. The high concentration of iron atoms and the energy of quartz give Amethyst a powerful, fiery radiation. Healing crystals "irradiated" in this way are stripped of information they have stored. Leave the healing stone on the druse for 6 to 24 hours, depending on the how long the stone was in use for. Leaving healing stones on the druse for longer will not cause any harm to the stone.
Placing healing crystals in a bowl of uncooked brown rice have also been proven to be an effective way of removing stored information from crystals. Some people believe they should cook and eat the rice afterwards, but I don't feel comfortable with this idea. With so many people starving on a daily basis I prefer to not waste food in this manner.
Healing stones can also be placed in a bowl of Citrine chips or on a Cirtrine druse. Citrine does not need any cleansing or clearin of it's own and is an excellent stone for clearning and cleansing other stones.
Reiki practitioners can use a technique called Jakikiri Jôka Hô to cleanse crystals, minerals and gemstones. This technique is good in situations when you only need to cleanse a few stones, but it can be time consuming if you are cleansing more than 10 stones as each stone should be cleansed individually when you use this technique.
In my opinion, laying stones in salt water or sea water, burying healing stones in soil or cleansing it in fire are definitely to be avoided, as many crystals will be severely damaged by this: Salt water penetrate pores and cracks and make the stone cloudy, some secondary minerals will be attacked by acids in the soil and transformed and fire will obviously tend to disperse too efficiently!

My preferred method of discharging and cleansing — all in one go — is to place the stones I used during treatments in a bowl containing 4kg of small (size 0 or 1sm) Hematite and 4kg of small (size 0 or 1sm) Citrine chips. I prefer to leave stones in this bowl for 24 hours, but this technique is so effective that it can discharge and cleanse stones in a matter of minutes.

Care

Physical cleansing should be restricted to eliminating dust from mineral groups and mineral druses. Use a fine paintbrush for the purpose. If you are cleansing a druse with water, only use mineral-poor water. Never use abrasive household cleaning agents on crystals. Some of them are almost impervious to such substances, while others are extremely sensitive.

Storage

It is very natural to want to display beautiful stones so you can see them most of the time. However, if you do not want regular dusting to become your main hobby, I recommend keeping them in a display cabinet. I would not recommend the windowsill, with exception to agate sections and other light-insensitive crystals such as rock crystal (Quartz), Hematite, Jasper, Lapis Lazuli, Tiger's Eye and Black Tourmaline. Many stones will lose their colour in direct sunlight, like Amethyst, Kunzite, Rose Quartz, etc.

Please don't lock crystals up in a dark box under the bed. Crystals, Gemstones and Minerals come to the surface to teach us, work with us and heal us through light and colour. By locking them up in a dark box you are keeping them from doin what they are here to do. In another post I'll talk about the Crystal Safe Haven I want to start, because I've heard of too many people locking crysals up in dark boxes ;-(

* WARNING: Placing certain crystals or stones in water can make the water toxic for consumption while other stones may be damaged by water. Some stones are light sensitive and it is not avisable to place them in directly sunlight. Consult with a qualified and experienced Crystal Healer if you are unsure.