In general, stone can take a lot of power, but you can get an effect where the surface is so cracked that the engraved area can flake and look uneven.
An example:
Your best bet will be to test a bit, people might recommend settings but your stone isn’t exactly like anyone else’s. Other glass/stone posts can give you a general idea, but overall I’d say you look like you’re already in the pretty good range… your engraves have good contrast, it’s just uneven on that material. It’s hard to say, and testing is really the only way to be sure.