The plane of Mineral is a rocky place full of precious gems and metals.. Some folks call it the Treasure Trove of the Multiverse. It is that, I suppose. Every sort of valuable rock a fellah can think of lies in the plane of Mineral.. You can't just go in and take whatever you want though. Most of the time, something'll stop you..
..This plane is lousy with critters that'll eat you as soon as look at you. Crysmals, xorn, khargra, end even a thoqqua or two lair here. Don't go to the Mineral plane without a good, sharp axe, I say"
Gaddin Hammerdome, dwarf miner
Checking these old Planescape manuals form the mid Nineties.. so many wonderful inspirations for concepts.
Here is a Gem Eater, a minute creature that inhabits the Quasiplane of Minerals. As the name says it only feeds of gems and crystals. They are territorial and tend to assume the colors of the most abundant crystal in the area. Males are not aggressive but females lay eggs in bigger creatures ears.