"I was given a piece of selenite by a ex boyfriend of mine 2ish years ago. I used that stone all the time. I carried it everywhere with me, work, school, driving, everywhere I went, it went with me. I recently met a girl who is getting into the metaphysical uses of healing crystals and I felt that I should give her my selenite because it served me well for so long. After her having it for a couple weeks she told me she was going to return it to me because it was giving her nightmares. This confused me, especially because selenite is a self cleansing stone. Is all my old energy left inside of it that's giving her these bad dreams? What would cause this stone to give her these bad dreams?"
Thank you so much for reaching out! You ask a great question! There are different beliefs around why something like this may happen. I personally believe that stones themselves do not emit negative energies or positive ones (I don't believe there really is such a thing as positive or negative energy -- it's all just energy). Instead, it's just that someone's body’s energy vibrations may not mesh properly with that of a specific stone at a given time.
Also, it is really important to cleanse crystals (even self-cleansing ones like Selenite) when it is going from one person to another and then charged by its new "owner." I think recharging your crystals is always an excellent way to bond with them and they will work more effectively for you. I would recommend moonlight (it doesn't have to be a full moon - you could use the quarters or even the New Moon) and/or a white candle. Selenite is a soft crystal so you do not ever want to use water around it since it could disintegrate the stone.
As for the dreams, again, everyone reacts to crystals differently. It's possible that the Selenite was holding on to your energy (if it wasn't cleansed before giving it to your friend). If your friend is particularly sensitive to the energy of crystals, she absolutely may have been feeling any energy from you in the stone.
I think it's really wonderful that you gifted her this piece of Selenite. If it still feels like it is meant to be hers, I would recommend that she cleanses it and then charges it and see how she feels. If that doesn't work, then it sounds like this particular stone was not meant to be hers.
I hope this helps!
DISCLAIMER: We feel that crystals can complement other therapies and support energetic well being. Crystals should not be used as a replacement for medical treatment. For medical advice, please consult a licensed healthcare specialist.