AU Hero's Duty Space Marine Ralph has an oval black Obsidian in the middle of his chest, his armor has a hole that fits around it, so it can still be seen.

Still figuring out a gem for Azure if I can get the time to go through his canon and take notes sometime, but at the moment, Lazurite is one of my top choices, but I definitely need more research.

Thinking his gem would probably be on his forehead maybe.

If I had regular Ralph in the game, I like the idea of him having a big square gem on the back of one of his hands, thinking maybe Carnelian for him.