I’ve never used any of the plated druzies out there, but I’ve found
all natural types to be perfectly durable enough to withstand
ultrasonic. For the record, the ultrasonic I use is a "baby"
ultrasonic, the type that costs $69 with no heater. Regardless, it’s
the only way I’ve found to clean them up. I just place them
upside-down and most of the dirt gets cleaned (shaken) off. Most
brushes don’t have fine enough bristles to really get down between
crystals and clean them to the sparkle that is achievable with
ultrasonic. As for steam cleaning, as I mentioned I don’t have one
so I don’t know for sure, but I think that at least the quartz
druzies would withstand the steam. Can anyone else out there share
any experience on this?