So I've got these crystals that are cloudy (and I've been told they're quartz), and they're probably in the weight of 5-10 lbs each. I'm trying to figure out where I could go to get them tumbled down into more manageable (and maybe sellable size).

Does anyone have any ideas? I hate to leave them out in the elements.

No idea. They seem too big to tumble. Have you considered breaking them, then tunbling them?