I've been using Tarnex silver cleaner on all of my jewellery for 38 years (except pearls). It has never damaged a single stone. I used to worry about porus stones like opal and coral but it never damaged them.
Me and my friend wanna meet you! We live in Ohio, not too far from Cleveland! Even for a cup of tea would be lovely. We wanna thank you in person for your service to the world. You've helped me through complicated times.