It's been my headcanon that the, for example, topaz's "geometry" leading to a defensive carbuncle is the crystalline structure itself, meaning the cut of the gem wouldn't matter in forming the carbuncle, only that there's a large enough gem to draw it out with aether.
I also RP as an ACN/SMN but I think Sounsyy already covered the important bits!
I also RP as an ACN/SMN but I think Sounsyy already covered the important bits!