Have you ever wondered about shape of the cut out around Rose's gem on Rainbow Quartz? I get the feeling it's more then a style choice.
It’s a fusion (ha) of Rose’s star symbol
and the pink diamond symbol Pearl has on her spacesuit (and would have presumably been on any outfit she had prior to the rebellion)
resulting in a symbol with the top half of a star and the bottom half of a diamond.
the diamond portion is likely a reflection of Pearl’s loyalty towards Rose. Even though they got rid of the diamond symbol during the rebellion, it likely still means ‘loyalty to Rose’ to Pearl. It would make sense for this to be reflected in Rainbow Quartz’ design, since she is the embodiment of the relationship between Rose Quartz and Pearl
we don’t yet know the exact significance of the star symbol in-universe, but I think its safe to say Rose didn’t use it prior to the rebellion (its not on her flag). It’s an important symbol of hers afterwards, though, and has some kind of significance toward these 5 particular Crystal Gems (Ruby, Sapphire, Amethyst, Pearl, and Rose Quartz) since its on the door of their temple. But Garnet, Amethyst, and Pearl don’t adopt the symbol onto their outfits until after Rose is gone (and Ruby and Sapphire don’t have star symbols on them at all) so its not a ‘uniform’ symbol of the Crystal Gems, at least not until after Rose became Steven.