Rainbow Number Four

Rainbow Number Four

Spring Mine ViewNear the highway only a short drive outside Custer, The Rainbow Four Mine is easy to access and has potential for a variety of minerals to be found.

When to visit: Spring, Fall, Summer (if cool)

What you can find: Black tourmaline, beryl, quartz, tantalite

What to bring: Rock hammer, sledge hammer, pick axe, chisels, bucket, backpack, water, snacks.

Where to stay: The town of Custer is 10 minutes away and offers hotels, camping, and food. Dispersed camping is allowed in the Black Hills National Forest all around this general area.

Getting there:

From Custer, South Dakota head west 5.7 miles and turn left onto FS Rd. 409 (Harry Mills Rd.) Drive 0.2 miles and you will see a turn off to your left. This is Site A and a good place to park.

(Site A: 43°43’46.0″N 103°41’47.6″W)
(Site B: 43°43’47.0″N 103°41’42.8″W)


Rainbow Number Four is a descent sized open pit mine that is easy to access from Custer and has a variety of pegmatite minerals. The mine is no longer active and working through old tailings or exploring the exposed rock in the mine can to find target minerals such as beryl, tantalite, tourmaline and quartz. This mine is known to have produced a number of other minerals, such as albite, alluaudite, heterosite, microcline, muscovite, siderite, triphylite, uraninite, uranophane, vanadinite and zircon. Site B is an area with large boulder tailings. Pale green beryl crystals have been found in these boulders. Using a heavy sledge hammer to break open the quartz boulders can reveal hidden minerals such as beryl. The forest service road that accesses this area is open from May 15 – November 15, the gate is closed the rest of the year. The mine is only 1/4 mile from the gate so you could hike in if you want to explore after the gates have closed.


(Sample gallery from Spring Mine – Rainbow Number Four Gallery Coming Soon.)


Related Articles