Final Fantasy XV Earth GemstoneWhile you’re playing the later story missions, after you’ve left Lucis, there will be one called Where She Lived quest. It takes place in Tenebrae, and includes following Aranea around as she dumps a bunch of info on you. When you get off the concrete bridge, you’ll end up on a plateau with several parked Imperial shuttles. Go around the first one on the right. Near the entrance, between the shuttle and the cliff, there will be a pile of crates. The gemstone is on the ground next to it.
Once you’ve got it, you can return to Cid (who’s either at Hammerhead or Cape Caem) and give him the item and the weapon. He’ll send you off, telling you to return in a couple of days. You’re gonna have to complete some quests and rest at least once before he lets you know the enhancement work is done. We suggest undertaking some hunt quests – ther’s a bunch of them all around, and they can be quite profitable.
Earth Gemstones can no doubt be found in other places as well, but we’ve only discovered this one. If you manage to find them someplace else, feel free to let us know in the comments. As soon as we’ve found more, we’ll update the guide with their locations.