Rose quartz and agate are the gemstones to hunt for in South Dakota. Large deposits of rose quartz can be found in Custer County. Agates can be found throughout the state, but the prized Fairburn agate, the state's gemstone, can only be found near Fairburn, in the Black Hills area.
Agate and Quartz
Agate is a variety of chalcedony, a form of quartz that occurs in volcanic rocks and characterized by fortifications or bands of differing colors. Minerals from the soil determine an agate's colors, which can range from the pinks, taupes and reds produced by iron oxide to the greens and blues produced by copper. Quartz is an easily recognizable mineral because of its translucence. Rose quartz exhibits a pale pink to rose-colored hue.
Where to Hunt
Head to the southwestern regions of the state to hunt for rose quartz and agate. Black agate can be found near Scenic, South Dakota. Fairburn agate can be hunted on thousands of acres of stony land around Fairburn, in Custer and Pennington Counties. Much of these lands are privately owned and you must obtain permission prior to gem hunting.
What to Look For
Agates are found as separate nodules or within geodes. An in-the-rough agate doesn't always bear much resemblance to the polished examples seen in pictures. Often, the fortifications and banding can not be seen due to an outer matrix covering the agate. A visit to a mineral shop or to South Dakota School of Mines & Technology's Museum of Geology, (see Reference 4) in Rapid City, will give you a better idea of what you are looking for.