There are many locations in Custer County, especially in the Challis area, where you can find gems such as citrine, quartz, amethyst, giant geodes, fluorite, diamonds, and a rare mineral known as zeolite. Further south, near Lime Creek, you could find agates and cryptocrystalline quartz. The Lost River area is also famous for amethyst and quartz crystals, which are plentiful in the Bayhorse and Yankee Fork Mining District. Often when you find amethyst, clear quartz will be found nearby.