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If you happen to be a rockhound living in (or passing through) Iowa, you may wonder what types of rocks and minerals can be found there and, more importantly – where to look for them. Although Iowa is not world-famous for its abundance of minerals, there are a variety of rocks to be found, one of which – the Keokuk geode – is recognized and sought after by people worldwide. It also happens to be the state rock of Iowa. These geodes and other stones are found in specific parts of Iowa and you’ll need to know these locations if you want to go rockhounding. So where should you go rockhounding in Iowa?
Southeastern Iowa is the best place to look – specifically near Keokuk. Geodes are also found in stream drainages and excavations in Lee, Van Buren, and Henry Counties. Generally, the best area to find great rocks is in a 70-mile radius around where the Mississippi and Des Moines rivers intersect.
Suppose you’re not very experienced in finding geodes and telling them apart from other rocks. In that case, you might benefit from a rock hunting trip where veteran rockhounds will teach you how to identify geodes, agates, and other stones that you’ll come across in Iowa. Many people walk right over a geode without even realizing what they missed. And geodes aren’t the only exciting thing you can find in Iowa – there are also meteorites and fossils.
If you want to check out the best book about rockhounding in Iowa, you can find them by clicking here (Amazon link).
Rockhounding Locations in Iowa
Though Iowa is not one of the most famous states for rockhounding, there are still some very interesting places to explore, primarily:
- Keokuk
Since Keokuk geodes are the signature rock found in Iowa, we’ll start there. The town of Keokuk lies in the southeastern tip of Iowa, right next to the junction where the Mississippi and Des Moines Rivers intersect.
This area is known as the “tri-state area” because it borders Illinois to the east and Missouri to the south. The state lines intersect around a shared 70-mile radius.
Most Keokuk geodes are unearthed in the city of Keokuk, inspiring the name association with these iconic geodes. However, the geodes can also be found spanning into Missouri and Illinois within that key 70-mile tri-state zone.
- “The Warsaw Formation”
The rocks in this tri-state region are part of an ancient, 300 million-year-old layer called “The Warsaw Formation,” dating back to the Mississippian period. The Warsaw Formation contains embedded rock units and fossils. This is the primary location where Keokuk geodes have historically been discovered.
Keokuk geodes are usually dug out from the lower section of the Warsaw Formation. They primarily come from soft mudstone deposits or harder dolomite rock beds. On average, the geode sizes found in mudstone tend to be smaller than those Unearthed from dolomite.
The geodes show a wide span of sizes, ranging from very small 1 cm examples to large 30 cm diameter pieces. But the typical Keokuk geode size averages around 7 to 12 cm across.
- Geode State Park
North of Keokuk sits Geode State Park, named for the Iowa state rock. Surprisingly, however, not many geodes occur there.
Regardless, it is illegal to remove any geodes found in the park. Regulations prohibit taking home geodes discovered on all public state park lands.
- Iowa Rivers
Like the Des Moines, Mississippi, Cedar, and Missouri Rivers, many rocks and minerals surface along Iowa’s key rivers and banks.
The reason river areas contain lots of minerals is due to erosion. The flowing water wears away at rock and soil, revealing more buried minerals at the surface over time.
For example, dolomite appears along the Cedar River near Backbone State Park and Palisades-Kepler State Park. While sandstone and limestone emerge in the Des Moines River valley, and carbonate rocks arise along the Mississippi River banks.
- Highway Road Cuts
Construction projects also bring more minerals to the surface. For example, cuts made in hillsides when building highways reveal hidden mineral deposits. Some good road cuts to check are Highway 22 near Muscatine by Wyoming Hills, Highway 9 between Churchtown and Lansing, and Highway 52 near Guttenberg.
- Quarries and Mines
Abandoned quarries and mines are also prime spots to search, but they can be hazardous. So, take safety precautions when digging around old quarries and mining sites.
TIP: Be careful if you decide to go to quarries and mines. Read this article on recommended safety equipment & tips for rockhounding:
Recommended Safety Equipment & Tips for Rockhounding!
What Rocks Can Be Found in Iowa?
I already told you about some remarkable rocks you can dig up in certain spots across Iowa. But believe it or not, there are a ton more neat minerals and fossils scattered everywhere around the state!
I want to show you an excellent chart that lays out ALL the different stones, crystals, minerals, and fossils discovered across Iowa over time. It maps out exactly where each kind is found – whether in certain rivers, parks, quarries, road cuts, etc.
| Category / Type | Locations |
|---|---|
| Rocks (Sedimentary) | |
| Conglomerate | Pleasant Township, Lucas County, Dallas Township, Marion County, between Red Oak and Coburg, south entrance of Pine Lake State Park |
| Sandstone | Allamakee County, Clayton County, Red Rock (Marion County), Sergeant Bluff, Sioux City |
| Siltstone | English River (Washington County), the Flint Creek bluff near Starr’s Cave Nature Center |
| Shale | Jackson County, Mason City, Rockford, Sheffield |
| Limestone | Des Moines County, Louisa County, Hampton Formation in Marshall County, Coralville Dam Reservoir – north of Iowa City |
| Chalk | Big Sioux River – between Hawarden and Sioux City, quarries near Grant City |
| Dolomite | A number of road cuts and quarries in northeastern and east central Iowa |
| Chert | St. Louis Formation in the Henry County quarry + quarries in Humboldt; Delaware, Jones, Clayton, and Dubuque Counties |
| Coal | Monroe, Mahaska, Wapello, Marion Counties |
| Rocks (Metamorphic) | |
| Quartzite | Northwest of Lyon County |
| Gneiss & Schist | River beds and gravel pits |
| Rocks (Igneous) | |
| Granite, gabbro, basalt | Northeast and central Iowa – fields, river beds, farms, lakeshores |
| Minerals | |
| Limonite | Iron Hill (Allamakee County) |
| Pyrite | Dubuque County |
| Marcasite | *Same as pyrite |
| Galena | Dubuque – along the Catfish Creek + near Durango |
| Sphalerite | Dubuque and Cedar Valley |
| Calcite | Eastern Iowa |
| Gypsum | Fort Dodge, Mason City |
| Quartz (including jasper, chalcedony, agate | Along the Mississippi River (Lee, Des Moines, Henry Counties) |
TIP: Real calcite is a unique mineral with exclusive properties, making it easily distinguishable from fakes. Find out the main differences between real and fake calcite in the article below:
Real vs. Fake Calcite: Focus on These 6 Differences
What minerals are found in Keokuk geodes?
Quartz is the most popular mineral discovered in Keokuk geodes. Additional minerals that contribute color to the quartz crystals are also found. These minerals include chalcedony (a variety of quartz), pyrite, marcasite, calcite, dolomite, aragonite, malachite, gypsum, hematite, smithsonite, barite, goethite, sphalerite and others.
The diversity of these supplemental minerals is responsible for the range of colors displayed by the quartz crystals within the geodes.
The quartz crystals in Keokuk geodes appear in various colors like blue, orange, yellow, green, red, purple, and gray; however, white and gray quartz crystals are most common. The assortment of extra minerals causes the colorful exhibitions of the quartz crystals, drawing interest to Keokuk geodes as unique geologic structures.
How do you open a Keokuk geode?
Geodes have a tough outer shell, so you need to break them open to access the beautiful crystals within. There are a few different techniques to crack geodes.
It’s important to know that some Keokuk geodes have hollow insides while others are filled with crystals. One option to open them is using a rock saw, which can cut the geode cleanly down the middle into two halves. This works well if you want to be able to polish the cut surfaces afterward.
However, a significant downside is that the saw could damage crystals in the center as it passes through.
Rather than the sawing method, you can also use a hammer and chisel. By tapping gently, cracks will form and spread bit by bit across the outer shell until it splits open. While not as neat, this approach lowers the risk of wrecking inner crystals.
Finally, a soil pipe cutter is convenient for opening relatively small geodes. This handheld tool has a wheeled jaw that applies even pressure as it is tightened around the geode. Once sufficient force is reached, the shell cracks open evenly.
However, large pipe cutters are costly. So, for geodes exceeding roughly 10 inches, it is more practical to use manual chisel and hammer techniques instead. The hammer strikes combined with chisel placement propagate fractures across the shell in a controlled way to split it open.
TIP: Some geodes can be dyed. Do you know how to find it? If not, don’t worry; I wrote an article about how to identify dyed geodes:
How to Tell if a Geode is Dyed: All You Need to Know
FAQs about Rockhounding in Iowa
Still did not find the answer to your answers about rockhounding in Iowa? Find frequently asked questions in the section below:
Are there rock and mineral museums or societies in Iowa?
The University of Iowa Museum of Natural History, the University of Northern Iowa Museum, the Madison County Historical Society, and the Sanford Museum & Planetarium have geological exhibits that feature rocks, minerals, and fossils from Iowa (some date back 500 million years).
Additionally, there is the Central Iowa Mineral Society, which has regular meetings and organizes different activities like auctions, rock hunting trips, rock trading events, and more. There is also a yearly River Valley Rockhounds Gem, Mineral & Fossil Show where people display and sell minerals and fossils.
Are there agates in Iowa? Which rocks in Iowa can be confused with agates?
Many different agates are found in Iowa, often near lakes and rivers. The Two rocks commonly mistaken for agates are (chert and jasper) which can have very similar colors.
What else can you find in Iowa other than rocks and minerals?
Fossils and meteorites are other specimens in Iowa, although fossils are much more common. Trilobites, stromatoporoids, brachiopods, gastropods, crinoids, bryozoa, cephalopods, and solitary and colonial coral fossils are among the most popular Iowa.
Freshwater pearls can occasionally be found in Iowa’s rivers within shelled mollusks, though this is rare. Petrified wood can also be found along some of the river banks in Iowa.
BTW: Do you want to know more about rock and mineral identification? The books listed below are the best ones you can find on the internet (Amazon links):
- Smithsonian Handbooks: Rocks & Minerals
- Gemstone & Crystal Properties (Quick Study Home)
- Ultimate Explorer Field Guide: Rocks and Minerals (National Geographic Kids)
I recommend the book Rocks & Minerals of Wisconsin, Illinois & Iowa: A Field Guide to the Badger, Prairie & Hawkeye States for further Iowa rockhounding details. I found this book very useful and well-written. You can purchase it here (Amazon link).
TIP: If you enjoy finding and polishing rocks or stones, you’ll know that there are two types of rock tumblers, one of which is the vibratory rock tumbler. Check out the complete guide about vibratory rock tumblers in the article below:
Vibratory Rock Tumblers: How They Work & Which One Is Best?