Diamonds also have certain planes of atomic weakness called 'cleavage directions'. This means the bonds between atoms in these crystallographic directions are weaker. If a diamond is struct with the right amount of force along these directions, more severe damage like splitting can possibly occur.
Some professionals remove the stone before doing any work on the metal, while others opt to keep it in place. It would also depend on the specific area of the jewelry item to be repaired, as well as the type of work that's required. It's always best to go for the long-term experts in the industry, who have a reputation for taking good care of their customers items, rather than going to just any small shop for a quick DIY tightening of ring prongs or bending of metal settings.
*Ideally, if permitted and not too lengthly, you can request to watch as jewelry item is being worked on. This can also prevent the potential risk of stone-switching. Cases of diamonds being switched out for cheaper imitations like cubic zirconia or nowadays even with lab-grown diamonds, do occur although uncommonly documented. Many jewellers in our industry maintain good ethics and would rather keep their reputations solid- never engaging in such activities, but be aware of the risk as it's always better to land on the safe side when it comes to high-value items like diamonds and jewelry.
(** Our laboratory does not perform any kind of physical repair-work on jewelry, we are stictly a third-party evaluator that administers gemological procedures to identify and obtain a grading opinion on your gemstones. We do insist each and every time that items at our facility must be checked in the presence of their owner or at least a representative, just for good ethical practice. This way, our clients can also benefit the most from their appointments with our gemologist, learning a bit about their item's beauty, rarity and proper care.)
