Speaking of the Senshi/Shitennou pairs. I was kind of curious why those stones in particular, right. Kunzite and zoisite are so unusual that I think only gemstone aficionados know them, and even though jadeite and nephrite are somewhat more commonly known names IIRC it still made people mess up the mineral names back in the day.
Well, uh, so, it was alleged that Takeuchi-sensei chose them to match the character and personalities of the senshi they're partnered with, so... Excuse me while I go overthink this and have a meltdown in suffering.
In the first place, supposedly the "inner senshi" are officially meant to be called "guardians"/"guardian deities" (守護 or 守護神). Haven't seen the raws, so I can't confirm, but that's what the JP media says. The term "Shitennou", as many are already aware of, are originally a term used to refer to a set of 4 Buddhist guardian deities.
If true then it just feels like they're all intended to be perfectly matching sets from the start, and it just never made it into the story.
I read that Sailor Moon was originally meant to just end with the Dark Kingdom plot, so maybe sensei intended to have a Romeo and Juliet sad ending where everyone just dies in the end?
These are all based on Japanese gemology guides (same as what I used to research for the Shitennou knight titles), since I imagine it's more likely to be the one Takeuchi-sensei had access to. These may differ from international ones.
In the manga sensei specified that the zoisite is the blue one, that's also known as "tanzanite". The blue variety of zoisite, among other things, means "calm and intelligence".
The connection to Ami/Mercury's character is very straightforward and obvious.
In terms of romance, a zoisite also means "subdued expressions of love". It really makes me think of how gentle this pair looks in the splash art sensei drew.