What if... just listen. What if in Steven Universe the location of the gems on their physical forms relates to the way they act. Think about it. With Rose, she is very motherly. Her gem is located on where her bellybutton is. Near the womb. With Both Pearl and Peridot, they are very knowledgeable and there gems are located on their forehead near where the brain is. With Lapis Lazuli, hers is located on her back to symbolize her water wings and also the fact that she was "stabbed in the back." I mean she was trapped inside a mirror for how long? Amethyst, her gem is located near her heart and even though I find that she is prideful, she still has a lot of heart for the ones that she loves even though she sometimes covers it up. With the Yellow and Blue Diamond, theirs is located in the middle of their chest. Could mean that they feel that they are the best. Meaning when someone refers to themselves where they always point to themselves in the middle of their chest.
Tell me what you think. I could be wrong about this, but it was just something I was pondering while I was trying to get some sleep. I haven't thought up a reason for Garnet and Jasper yet. If you think of any or think my reasons are wrong feel free to comment. As for now... Peace