I've heard of strong detergents actually pitting surfaces, if left on for a long enough time, but it would depend on the type of crystal or stone, and if it was suseptible or not.
Water in the cracks, and then exposing it to outdoor winter temps (in a pocket or on a necklace or something) would harm it because water expands & contracts, forcing the crack wider. But in regular indoor house environments, I don't think there's anything to worry about. I'd be more worried about a crystal on a necklace pendant swinging forward & hitting the side of the car as I unlock the door, in winter--THAT can cause damage.
Treat them like glass & you'll be ok I think.
(Don't give a salt bath to anything that can rust, like iron pyrite, it's just common sense).
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I'm not going to vacuum 'til Sears makes one you can ride on.