I bought my selenite plate mostly because it was cheaper than I expected and I figured I'd find a use for it eventually. It sat in its box on my dresser for almost two months.
I didn't understand what it was for
I'd read that selenite could be used to reset other crystals, but I didn't have a collection big enough to think that mattered. I mostly just thought it looked nice, so I finally set it out as decoration and left it at that.
The night I actually tried it
It was almost an accident. I was clearing off my dresser and set my amethyst on top of the plate without thinking much of it, just to get it out of the way. I left it there overnight because I forgot about it, not because I planned anything.
What I noticed the next morning
I picked the amethyst back up and it felt different in my hand — cooler, lighter somehow, though I know how that sounds. Selenite is an emitter, believed to put out a steady frequency without holding onto anything itself, which is part of why it doesn't need cleansing the way other stones do.
It's a habit now, not an accident
I keep the plate on my dresser permanently now, and whatever I've been using most during the week ends up on it before bed. I still can't tell you exactly what it's doing. I can tell you my stones feel more like themselves after a night on it than they do after weeks without.
If you've got a selenite plate sitting unused somewhere, it might be worth more than a shelf.