First I would cleanse them by either washing them in water, imagining white light pouring into them or placing in your garden (in contact with the earth) or all of them.

Then use your intuition and note on paper how each crystal makes you feel and whether you would like to place them on certain chakras. There are so many sources of information that say 'this crystal is good for this' but your intuition is the best way to tell you which crystal is good for you and what they will help you with.

So in answer to your question, IMO, yes they can be.