Man, I can't get over how gorgeous your gem designs are... How do you pick out the gems that inspire your designs? I'd love to make one for myself, but have a hard time taking those first steps.
Gosh there's so many. With the Agates series I knew about some of them and just looked up more of them until I found a lot more of them. I randomly stumble upon most of them so even thinking about it is overwhelming so I understand why you're having a hard time. Sometimes it's looking up characteristics (specific colour, iridescence, particular element in it). There's some resources that'll randomly generate gems for you. Some blogs are out there to help with finding gems for OCs specifically.
https://gemsona-hq.tumblr.com/tagged/Monthly-Gem-Challenge (more Steven Universe related, but works for LotL as well. A brief description on a random interesting gem/mineral of the month (they also have prompts for drawing). The blog is on hiatus however, especially since Steven Universe ended.)
https://www.mindat.org/ (a more scientific resource rather than pseudoscience/metaphysical stuff. They have a search by properties which allows you to look up a mineral by say colour, hardness, lustre, elements included, etc. They have a lot in their database and I use this mainly for LotL involved Gems, especially in my Jojo crossover one)
https://www.gemdat.org/ (it's sort of the sister website to mindat. It's a lot less sciency and numbers and a lot easier to understand and has a random mineral generator. And a search by colour that you can pick from. It doesn't have as many minerals listed as mindat but sometimes that's better. But once you pick one from there you can always go to google to find more info on it.)
Iris Agate's Comments