That may have been kind of a fluke thing. People use them all the time on colored stones. I have different ring size holders, and very often people try stones in them. Lay the stone flat on it''s table, and don''t get a prong right over on the sharp corner.
I use one on mine all the time, you have to be careful not to snap it on the stone and make sure that the part that goes over the top doesn't dig into a facet.