This is about charging your stone. You can wash your stone with water. Next you want to place it where the sunlight hits it directly. And viola! Your stone is charged! What happens prior to that is that your stone may not be effective due to carrying negative energy. For instance, when you first buy your stone, it has already been handled by a lot of clients. Their energy goes into it. Believe me, I have seen stones turn specks of dark color when handled by a person who has a great deal of emotional troubles.
There are people who charge their stones with moonlight. Since moonlight reflects the sun it is somewhat of an indirect charging. Nevertheless it works. Moonlight is not as intense so it will not discolor sensitive crystals. Both sunlight and moonlight are very energizing to crystals. The idea of charging your crystal/stone is to bring it to full charge so that it can work more effectively.
Other methods of charging stones/crystals is to place it by plant leaves or to bury it. You may also use sacred water to clear your stone of negative energy. Do a prayer intention if you don’t have sacred water.
A crystal/stone should be charged for 24 hours to be fully effective. This way, it will do the job that it was designed to do. Sensitive people can pick up signals from stones. The more silent you become, the clearer the message.