Given its lack of dramatic mountains, you might be forgiven for thinking there isn't much gem mining in Iowa going on. But as it turns out, there are wonderful crystals and other treasures to be found in the state. From quartz and chalcedony and other minerals in geodes, to agates and freshwater pearls, Iowa is home to quite a few unique gems.
Geodes in Iowa
Collecting geodes is one type of gem mining in Iowa. A geode is a roundish rock that houses an interior of crystals. In Iowa, the geode was declared the official state rock in 1967. Most geodes range from two to six inches in diameter. The kinds of crystals within geodes can vary, and in Iowa, several minerals may be found inside different geodes. The largest concentration of these geodes is found within an approximately 35-mile radius of the town of Keokuk, Iowa.
Iowa boasts the remarkable distinction of having the greatest number and types of geodes in the world. Quite often they can be found along the outcroppings of the Mississippi River, primarily in the general vicinity of its intersection with the Des Moines River.
Some Keokuk geode interiors contain quartz that is transparent to white. Other geodes contain chalcedony, which covers quartz in layers of pink, gray, white, yellow, blue and orange. Still other geodes contain calcite. Iowa geodes are most commonly found in southeastern Iowa stream drainages, particularly in Henry, Lee and Van Buren counties. You can find them primarily in the Warsaw Formation, which is an ancient strata of shale and limestone.
Agates in Iowa
Composed primarily of chalcedony and quartz, agates are highly sought-after stones with beautiful layers of many colors. Various civilizations, including the ancient Greeks, commonly used agates when making art and jewels. Your chances of finding agates in Iowa are particularly good in northeast Iowa; the shores of Lake Superior are traditionally a good source of agates.
Freshwater Pearls in Iowa
One gemstone in Iowa with a fascinating history is the freshwater pearl. During the 1800s, mussels were farmed from the Mississippi River mostly for their pearls. When German button maker John Frederick Boepple settled in Muscatine, however, freshwater pearls became a sensation.
Boepple opened a button factory in Muscatine in 1891, where he produced mother-of-pearl buttons. Eventually, the town became so famous for these buttons that it billed itself as the Pearl Button Capital of the World. The attractive American buttons outsold European ones at the time. With the introduction of plastic buttons, however, the button business eventually folded, but the freshwater pearls remained an attractive material for factories overseas which used them as beads.
Hunting for Iowa Gemstones
While there is no commercial gemstone mining in Iowa, opportunities abound for finding your own. Depending on the gemstones you seek in Iowa, you will need to search in different areas and use different tools. For geodes, eastern and central Iowa is a good place to start. Search portions of the Warsaw Formation, in stream channels. Most geodes are small, but some can reach the great size of up to two feet across.
These mostly round, sometimes cauliflower-like rocks can be split with either a rock hammer or a bricklayer’s hammer. This reveals the crystal interiors that make geodes so prized. Always wear protective eye covering when hammering. Keep in mind that many geode sources are on private land. Before you set out on your geode hunt, be sure to obtain a permit, and do not collect geodes on parkland.
For agate hunters, explore northeast Iowa’s shores and rock bars after spring floods have rearranged rocks. Look for translucent rocks among the ground cover. Given their pink, orange, maroon and brown coloring, agates are sometimes confused with chert or jasper. Agates catch the light differently as they are translucent, which sets them apart.
About the Author
J. Dianne Dotson is a science writer with a degree in zoology/ecology and evolutionary biology. She spent nine years working in laboratory and clinical research. A lifelong writer, Dianne is also a content manager and science fiction and fantasy novelist. Dianne features science as well as writing topics on her website, jdiannedotson.com.