Jubian diamonds

Small, translucent gemstones found only on Jub. If you're willing to pay the price, they can be found in the middle of the jewelers' section of the central market. The gems are forged naturally over the course of centuries in three massive, heavily-guarded volcanoes visible from the capital. They are painstakingly mined from partially cooled lava flows at great personal risk to the miners. Then, based on long tradition, they are individually hand-carried to the official processing center where each one is authenticated, appraised and given a unique molecular tag.

That's what they tell the tourists, anyway. Actually, the diamonds are Jubian rock beetle excrement.