everyone has noticed how all the crystal gems have star motifs on them, but amethysts are different.
they are torn in, maybe representing how she thinks shes a mistake, or not a true member,but get this, greg used to wear a star too, even before he and rose had steven
In serious steven garnet mentions that both gems and humans died on the battlefield
. Greg get’s visibly uncomfortable when the war was mentioned, and says “It’s not like I was there”
My theory is that greg /was/ there during the war, and was one of the few survivors. After the war was won, he became a rock star using the armies insignia as on his shirts. Rose heard about this and went to see a concert, they meet, get in a relationship and have steven. Him being a gem war veteran might also explain his fear of ‘gem stuff’. There also seem to be various shape insignia outfits. The gems have stars, the home world gems have diamond, but what else? Pearls space suit has a diamond insignia on it, possibly indicating previous home world affiliations.
but not only that, ruby and sapphire have square motifs on their chests, indicating an entirely different faction, and the fact that they became part of the star group after fusing.
but theirs also another faction.
the triangle faction. Who do we know who may be a part of the trianlge faction? Lapis
This could be considered a diamond, like peridot and jaspers, but I think it looks more like a triangle.
tl;dr: In the gem war gems from the diamond, triangle, and square factions joined the star faction with humans, including greg who later used a star as his own insignia. Pearl was from the diamond faction, garnet from the square, and lapis is from triangle.