Are ultrasonic cleaners safe for sterling rings with turquoise, agate, or onyx stones?

Solid metal usually cleans well in an ultrasonic cleaner. Soft stones, oil treated and color treated stones are not recommended for use in an ultrasonic cleaner. Soft stones are not structurally strong and may have internal cracks, which will not allow them to stand up well against the ultrasonic cleaners high frequency. For these reasons, turquoise is not recommended; however, agate and onyx should be ok if there are not cracks in the stone.