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If you happen to be a rockhound living in (or passing through) Iowa you may be wondering 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 all over the world, and also happens to be the state rock of Iowa. These geodes and other rocks 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 the town of Keokuk. Geodes can also be found in stream drainages and excavations in Lee, Van Buren, and Henry Counties. Generally, the best area to find great rocks is considered to be in a 70-mile radius around the point where the Mississippi and Des Moines rivers intersect.
If you’re not very experienced in finding geodes and telling them apart from other rocks you might benefit from a rock hunting trip where veteran rockhounds will teach you how to identify not only geodes but also agates and other rocks 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 interesting thing you can find in Iowa – there are meteorites and fossils as well.
If you are interested in checking out the best book about rockhounding in Iowa you can find them by clicking here (Amazon link).
Rockhounding Locations in Iowa
Although Iowa is not one of the most famous states in terms of rockhounding, there are still a few very interesting places for rockhounding. You can read about them here:
Since Keokuk geodes are the most famous type of rock to be found in Iowa – I’ll start with those. Keokuk is a town in the very southeast of Iowa, right next to the junction where the Mississippi-Des Moines rivers intersect.
This area is called the tri-state area since it shares a border with Illinois to the east and with Missouri on the south side.
Keokuk is where most of these geodes have been found, which is why it’s called the Keokuk geode. These geodes are actually found in not only Iowa but also Missouri and Illinois (the 70-mile radius mentioned above covers the other 2 states as well).
- “The Warsaw Formation”
All 3 states have something called “The Warsaw Formation” in this region.
This is basically a very old (approximately 300 million-year-old) rock unit that contains other rocks and fossils dating back to the Mississippian period. Keokuk geodes are primarily found in this formation.
Keokuk geodes are dug out of the lower Warsaw Formation, mostly out of mudstone or dolomite. Geodes found in the mudstone are usually smaller compared to the ones found in dolomite.
The size of a Keokuk geode can vary a lot ranging from 1 cm to 30 cm in diameter. The average size is 7 to 12 cm.
- Geode State Park
North of Keokuk is Geode State Park, which is named after the state rock, though you won’t find many geodes there.
A word of warning – even if you do find geodes there, it’s illegal to take them (it’s actually illegal to take any geode out of any state park in Iowa).
- Iowa Rivers
Many rocks and minerals are found along the rivers of Iowa including The Des Moines, Mississippi, Cedar, and Missouri rivers.
The reason river banks and river valleys contain a lot of minerals is that the running streams cause erosion which exposes the minerals on the surface of the Earth.
For example, dolomite can be found at Backbone State Park and Palisades-Kepler State Park, which is next to the Cedar River, sandstone and limestone can be found in the Des Moines River valley, and carbonate rocks can be found along the Mississippi River.
- Highway Road Cuts
Construction also exposes a lot of minerals and highway road cuts are a good place to look, for example: on Highway 22, near Muscatine there is the Wyoming Hills cut, the Highway 9 cut (from Churchtown to Lansing), and the Highway 52 cut near Guttenberg.
- Quarries and Mines
Finally, quarries and mines are a great place to go rockhounding, but they can be dangerous places to hunt, so be careful in these areas.
Be careful if you decide to go to quarries and mines. Read this article on recommended safety equipment & tips for rockhounding:
What Rocks Can be Found in Iowa?
I already mentioned a few types of rocks that you can find in different locations, but what other rocks can you find in Iowa? Below is a chart that shows pretty much everything you can find in Iowa and where they’re found.
|Category / Type||Locations|
|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 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|
|Quartzite||Northwest of Lyon County|
|Gneiss & Schist||River beds and gravel pits|
|Granite, gabbro, basalt||Northeast and central Iowa – fields, river beds, farms, lakeshores|
|Limonite||Iron Hill (Allamakee County)|
|Marcasite||*Same as pyrite|
|Galena||Dubuque – along the Catfish Creek + near Durango|
|Sphalerite||Dubuque and Cedar Valley|
|Gypsum||Fort Dodge, Mason City|
|Quartz (including jasper, chalcedony, agate||Along the Mississippi River (Lee, Des Moines, Henry Counties)|
What minerals are found in Keokuk geodes?
Quartz is the most common mineral in Keokuk geodes but you’ll also come across chalcedony (though this is a form of quartz), pyrite, marcasite, calcite, dolomite, aragonite, malachite, gypsum, hematite, smithsonite, barite, goethite, sphalerite, and a variety of other minerals, which are generally responsible for the coloring of the quartz crystals in the geodes.
Crystals of many different colors can be found inside Keokuk geodes including: blue, orange, yellow, green, red, purple, and grey – though white and grey are more common.
How do you open a Keokuk geode?
Since geodes have a hard external shell you need to crack them open to get to the beautiful crystals inside, and there are several ways to go about this.
Keep in mind that some Keokuk geodes have hollow interiors whereas others are completely filled with crystals. First off, you can use a rock saw – which is great if you want to polish the ends of the two halves once you’re done.
The problem with using a rock saw though, is that you might damage the crystals in the middle of the geode when you’re cutting through it.
Secondly, you can use a hammer and chisel to score a line around the geode till it cracks, then use a screwdriver to pry it open. This takes a bit of time and if your geode isn’t very large then it’s better to use the last method.
Finally, the most convenient way (for relatively smaller geodes) is to use a soil pipe cutter (wheeler type) which distributes the pressure evenly around the geode and cracks it open when a bit of pressure is applied.
Large pipe cutters are expensive though, which is why it’s better to use a chisel and hammer when you’ve got a geode bigger than approximately 10’.
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:
FAQ 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 of which date back 500 million years).
The Central Iowa Mineral Society holds regular meetings and organizes auctions, rockhounding trips, rock swaps, and other interesting activities. There is also an annual River Valley Rockhounds Gem, Mineral & Fossil Show where people display and sell their minerals and fossils.
Are there agates in Iowa? Which rocks in Iowa can be confused with agates?
There are many different types of agates in Iowa which are often found near lakes and rivers. The two rocks most commonly mistaken for agates are chert and jasper which can have very similar colors.
What else can you find other than rocks and minerals in Iowa?
Fossils and meteorites are two other specimens you can find in Iowa, although fossils are much more common. Trilobites, stromatoporoidea, brachiopods, gastropods, crinoids, bryozoa, cephalopods, solitary and colonial coral fossils are among the most popular in Iowa.
Freshwater pearls are also found in Iowa – to find these you’ll need to find shelled mollusks in the rivers of Iowa – though this is quite hard and a rare occurrence. Petrified wood can also be found along some of the river banks in Iowa.
BTW: Do you want to know more about rocks and minerals identification? The books listed below are the best ones you can find on the internet (Amazon links):
- The Crystal Bible
- Smithsonian Handbooks: Rocks & Minerals
- Gemstone & Crystal Properties (Quick Study Home)
- Ultimate Explorer Field Guide: Rocks and Minerals (National Geographic Kids)
If you want to know more about rockhounding in Iowa or you prefer paper books, I recommend buying a book Rocks & Minerals of Wisconsin, Illinois & Iowa: A Field Guide to the Badger, Prairie & Hawkeye States. I found this book very useful and clearly written. You can buy it here (Amazon link).
TIP: In this article, you read about the best places for rockhounding in Iowa and what rocks you can find in this state. If you need similar information for other states, click on the link below to see guides about rockhounding in other states in the USA: