You're right, I certainly don't want to endanger his life. Most of the reason I wanted to use them was that they were already there. But now that they gave me the idea for it, I might just have to order some quartz and see how that works. Thanks!

P.S. I might experiment with a piece of selenite and a sealant to see how water-resistant they are, but I'll probably stick with the quartz crystals.