It depends. There are a couple of ways, one can do this and it all depends on the stone or if your speaking about crystals, than it depends on the crystal. If you know the name, than it is something to research, or if you don't go with your intention.
Some crystals like rose, and opal do not like the sun, putting on a window cell would be enough to charge them underneath the moon light. Stones like Sun stone would rather be in the sunlight, you can always put than in the earth. Make sure to leave some sort of object behind, so you know where it is to dig it up next time.
I normally leave them to cleanse or to charge, for a day, if I were to burrow them I could leave them there for at least three days.
Some use selenite, which is sold in flat disks (good for placing other stones, gens or rocks as well as jewelry) and more commonly they are sold in tower pieces. Keeping stones near them will automatically cleanse away negative energy but you can get into a ritual about cleansing them once a month or more if needed. Also, selenite isn't that expensive so it is a very useful tool to have.
Moonwater is another means of cleansing. You can make your own (recommended) which is simply leaving out a bowl of water under a full moon and then relocating it to a container for storage. You can cleanse your rocks and crystals in this type of bath, or you can leave them out (rocks/crystals) overnight under a full moon to get the same effect.
Salt is another inexpensive means of cleansing. I place salt in a decorate box and use it mostly for my quartz. I place the stone inside and leave it there for several hours. salt is a natural protective means (hence why many use it to create a casting circle with).
I have not charged my crystals in the sun, but I do give them sun baths where I will place them in a window sill to take in the light when I am planning to use them for casting or other means.
