Danubrite has a Mohs of 7 so is good enough for mounting but prone to chipping. If the stone is encapsulated it shouldn't be a problem. Yellow and Pink are worthy of mounting but the clear is as cheap as chips so if damaged could be replaced quite easily.
It's the customers call in the end so advise them of the vulnerability.
Certainly Danubrite is not a stone to be worn in an everyday ring.