I would expect most gemstones to be inert, but would test it just to be safe. Place some in an open container of tap water and use another with just water for a control. After 24 hours, if KH, pH, and TDS are the same, you should be fine. I've never tried or heard of anyone trying them in a shrimp tank, though. If any metals or so forth were to leech, I'd expect this to be a bigger problem with shrimp than it would would for fish.
Nothing good happens fast in an ecosystem.