(No worries, kuiper!)
Hm… see the thing is, black beryl is actually white/colorless beryl (Goshenite) that has a lot of black spinel inside. So Black Beryl would be a pretty cool fusion idea for a Goshenite and a Spinel but not really a good component gem in and of itself.
Maybe we could use that same color theory reasoning, though? So Sakura is a permafusion Morganite and her two component parts are Goshenite and Bixbite (so white/colorless dilutes the red to make pink)? Goshenite’s white/lack of color could be Inner!Sakura’s monochrome animations style or Bixbite’s red could represent Inner!Sakura’s passion. Hrm, but Goshenite means truthfulness while Bixbite is about harmony so that’s the opposite.
… maybe Shizune is Black Beryl and since both she and Sakura share the Goshenite aspect that could represent their medical training from Tsunade? (Or the sassiness they’ve gotten from her.)
@kuipernebula: given sapphire and rubies are somehow different types of gem despite both being corundum, i don’t think we have to worry too much about what make the gem the color it is
That’s true, canon SU is pretty lax about gemstone naming/choices…