Oh and shall we teach you the entire Botanical Knowledge of the Shamans right here on yahoo answers as well?

Its all much of a muchness, your probably referring to scrying were you gaze into a crystal ball. You can do that with anything from a bowl of water to staring at yourself in the mirror whilst in the dark. all you are doing is altering your state of consciousness whilst staring and focusing on a single spot over a period of time.

Crystals are used in wicca for healing and spellwork. You will have to do some research to find the correspondences for them. There are many books on the subject as well.
Crystals balls are for divination, like tarot, oracles, pendulums, scrying bowls and black mirrors. You have to choose which one you like best.

while I'm not a Wiccan and don't encourage you to go that route, I must say---if you're interested in learning about something like this:
a) go find a reputable book about the subject and read up
b)find someone in your community who practices and can teach you the ropes. I'm sure there are some around!
I think that will be much more helpful to you than Yahoo Answers 🙂

I recommend you read "Forbidden Rites" by Jeanette Ellis. She is very passionate and knowledgeable about crystals, and there is a very long, encyclopedic chapter on crystals in her book.
Is a crystal ball a good investment? That depends on how good you are with a bowl of water (use a black ceramic bowl filled with water and scry in candlelight). Much cheaper and possibly very effective. If that doesn't work for you, make a magic mirror by painting an old clock glass with black paint (paint the side that curves outwards and back that with silver foil). Then try a crystal ball. Most of these are made of glass and they are much cheaper than quartz balls. The most expensive ones are made of beryl and these are decidedly beyond most people's budgets!
Crystal balls are used for scrying ... you see visions in them. Their normal use is divination or guidance. But they have also been used for telepathic communication (as in 'The Lord of the Rings' for instance).
I have a glass ball, but I find a magic mirror works best for me ... you can buy these readymade too (though it's best you make your own if you can), and they are cheaper than quartz balls.
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Safety Warning - if you do buy a crystal ball or glass ball of any description, never leave it uncovered in daylight. If the sun gets to it, that's a powerful firestarter. Crystal balls respond well to moonlight, but they don't like the sun. They are also very easy to drop on your toes and fingers, and they are very heavy, so it really hurts!