How to safely remove pricing sticker residue?

I got a peach moonstone recently, but it came with a pricing sticker that left tacky residue that simply won't come off. I've tried soap and water, as well as a magic eraser. It's also too sticky to scratch off with a fingernail. I'm afraid to try solvents for fear of damaging the stone. What would you recommend?

I also have a golden sheen obsidian with the same residue issue. Wondering if maybe nail polish remover is safe to use on these two stones?