When Keystone Motel aired we got our first good look at Ruby and Sapphire. Their appearance in Jailbreak was very brief and they were both very focused on finding each other, so it didn’t help us much.
We’re not saying that they were acting normal in Keystone Motel either. They were both under a lot of stress, meaning their behavior was skewed. Their reactions to stress are quite interesting though, and we get to see other sides of them towards the end. They are very different, and while real rubies and sapphires are just different colors of the same mineral, corundum, the only similarity Ruby and Sapphire seem to share is temperature control that goes haywire when they are angry. Otherwise they don’t seem to have much in common.
They’ve been in the Crystal Gems for a long time though. What are normal Rubies and Sapphires like on the homeworld, where Gems don’t inter-mix very much? We can make some guesses.
Ruby is an eternal flame, baby. If there’s one thing we can say fairly conclusively about her, it’s that she doesn’t handle stress well at all. Both of her appearances so far have shown her reacting violently under pressure, and she has displayed a general inability to see past her rage whether it be her missing that Steven has freed himself from his cell or not noticing that she’s underwater and therefore her rant is unintelligible.
She’s small, but like Amethyst claims to be she seems to be quite scrappy. If any one of the Crystal Gems we know was (successfully) built for war then it’s Ruby. Her blind fury could be quite powerful on a disorganized battlefield (which it likely would be, as Gems don’t seem to fight in formation), leading her to attack the enemy hard; even if she was reckless and got poofed, it’s only a minor risk since another Ruby might charge the enemy before her gem can be shattered. Plus, she seems to manifest very strong fire powers when angered. Several angry Rubies in the middle of a group of enemies could make the battlefield very difficult for softer enemies.
It’s difficult to get a feel for Ruby’s strength level. In most cases (Rainbow Quartz being the very big exception), the mass of a Gem’s physical form seems to roughly correlate to strength, indicating that Ruby is roughly as strong as Amethyst and Pearl.
Magical ability doesn’t seem to be represented in size (Lapis Lazuli is physically weak to match her slight frame but she is incredibly magically powerful), so Ruby’s overall strength might depend on how powerful her fire magic is. Until we see her in a fight, however, we won’t know how she stacks up. Her stature and demeanor don’t seem to indicate that she would be particularly high up in the Gem hierarchy, so our current assumption is that she is a lower-end soldier class meant to disrupt the enemy so that stronger, more valuable Gems have an easier time breaking them.
Sapphire is as cold and in control as Ruby is fiery and excitable. She is the source of Garnet’s future vision and seems to have roughly the same proficiency with it that Garnet does. Though she may focus on the future to the detriment of the present, maybe even looking ahead to a happier future to not have to deal with an infuriating present, Sapphire is still much better at handling stress than Ruby—even if that doesn’t say much.
It can be difficult at first to think of a place where Sapphire would belong on the homeworld. Perhaps the difficulty in imagination can be aided by removing a bias is very easy to form: the assumption that the shorter (and weaker) the Gem, the more common it is. For some roles that probably makes sense – if Ruby is a soldier then you’d expect the grunts to outnumber the elite – but elsewhere there could easily be roles that, despite being rare, don’t require a powerful Gem to fulfill them.
After all, with much more regal attire and bearing, Sapphire gives the impression of being of a much higher rank than Ruby. Her future vision might give her a very respected role in the hierarchy, even if she’s just an adviser to the ones who actually make the decisions. If Pearl was a servant to Rose Quartz then Sapphire may have been her oracle, giving Ruby access to Rose’s inner circle by virtue of her relationship with Sapphire.