You know what’s kind of exciting? Since gemstones are pretty much just elements and minerals compressed by gravity and and heat (and gravity and heat and those same elements exist pretty much throughout the known universe) it’s very likely that alien races, no matter how different their biology is from us, are going to encounter more or less the same gems and gemstones we have. So a planet of beings we could scarcely comprehend and that could scarcely comprehend us could watch a marriage proposal and still understand that a grand gesture of emotion is being made because, wouldn’t ya know, they exchange those same hyper compressed nuggets of carbon to express their affection too? What a wacky coincidence!
And then maybe there’s life in other places where the composition of their planet is vastly different and almost exclusively corundum and they have enormous mountains of emerald and sapphire and its their favorite building material because its so common and pretty and then they come to our planet and they’re like look! look at what those humans are wearing! and its emeralds and sapphires and they realize how highly we value and adore the basic building blocks of their home planet and their entire species just swells up with pride because those little squishy pink and brown aliens think their world is just as beautiful as they do.
And we all achieve a greater understanding and appreciation for each other because no matter how differently we may function or behave we all have a special appreciation for these colorful little lumps of pressure and heat that goes beyond our vastly different biology.
Diamonds are a sentient beings best friend!