116 3rd St SE
Cedar Rapids, Iowa 52401
As we ambled along Prairie Park Fishery Lake’s shore an unusual rock caught our eyes.
Nestled within hundreds of fist-sized chunks of gray limestone was a sharply angled rock the color of caramel candy. When we picked one up, it felt smooth and waxy and had sharp edges.
It linked us with human history.
Conditions were perfect that day for seeking rocks. Months of low rainfall had dropped the lake’s water level, revealing thousands of multicolored stones. Some were high and dry while others glistened in clear, shallow water.
Bill Desmarais, our friend and retired earth science teacher, identified the caramel rock as chert. Later research revealed its exciting history.
Chert is the same as flint. Found around the world, this humble rock, so common in the Cedar Rapids area, was the primary raw material for tool making for thousands of years.
Spear and arrow points crafted from it felled animals ranging from mastodons to more modern bison and deer. Knives made from the same rock rendered their huge bodies into meal sized chunks. Chert was invaluable for tools until metal gradually replaced it.
Although old muskets were called “flintlocks,'' often it was a piece of chert that struck against iron after the trigger was pulled. This sent a torrent of hot sparks into gunpowder that exploded and sent a ball toward a deer, bison or human enemy. Today people still enjoy picking up chert.
One of life’s pleasures is sharing nature’s wonders with kids, so a few days after we found chert near our Cedar Rapids home, we invited an 11-year-old neighbor to go rockhounding. He scampered along the shore finding chert, granite, odd shaped limestone and sticks recently chewed by beavers, all inside Cedar Rapids city limits.
Kids love rocks. They’re fun to throw and come in such a variety of shapes, colors, textures and densities that they stimulate curiosity about nature.
“Rockhounding is a fun and inexpensive family activity that can grow into a passionate hobby or even a fulfilling career in geology or engineering,” said Ray Anderson, a retired Iowa geologist. “Fortunately, Iowa is an epicenter of opportunities to find diverse rocks.”
“Iowa’s bedrock is mostly limestone. Kids love fossils and since limestone was formed by living creatures in ancient seas it is often filled with the impressions of long extinct animals. They are exciting for kids to discover,” said Marv Houg, President of the Cedar Valley Rocks and Minerals Society.
When we asked Desmarais and Houg where Iowa’s best places to discover rocks are they responded with enthusiasm — and caution. The caution was simply: Make sure it’s legal wherever anyone collects rocks. Some of the best locations are on private land and collection may be prohibited in some public parks.
“Ask first,” they caution.
Then they went on to share some of their favorite gathering places. We live in the geode state, and perhaps no other rock is as surprising or fun. The exterior of our state rock is ordinary looking and roundish. Split it and a gorgeous array of colorful crystals sparkles from the hollow interior.
“Geodes are most common in an approximately 30-mile diameter circle around Keokuk in Iowa, Illinois and Missouri,” Houg said.
Some people who own geode-rich land allow people to collect for a fee, usually based on a five-gallon bucket full.
“This is a productive and legal way to find them. It’s a good idea to wear old clothes, sturdy shoes, and bring along a pick and shovel to help extract them from the dirt,” Hoag said.
The Keokuk Area Convention and Tourism Bureau can help people locate private landowners who welcome collectors for a fee. The organization also sponsors an annual Geode Fest. It’s scheduled for Sept. 23-25 this year.
A fascinating and visible rock is hard to claim as Iowa’s own. Waves of glaciation picked up massive boulders from the Canadian Shield in Minnesota and further north. It took eons for the slow-moving ice to inch rocks south. As the climate warmed the ice melted, it left roundish glacial erratics that people discover today. Many are granite, but erratics can of different types of stone.
The giant rock in Cedar Rapids’ Bever Park and the even bigger one in Marion’s Waldo’s Rock Park are erratics that kids love to clamber on.
The 2022 Gem, Mineral and Fossil Show is March 26-27 at Hawkeye Downs Expo Center, 4400 Sixth St. S.W., Cedar Rapids. Rock ID, tumbling, knapping and panning will be discussed. Displays of agates, Geodes, minerals, crystals and fossils. Suggested fees: Adults $3, Students $1, Children under 12 and youth groups with an adult are free. Website https://www.cedarvalleyrockclub.org
The Cedar Valley Rocks and Minerals Society invites anyone to their monthly meetings. Information is on their website. Other rock clubs are found in cities throughout the United States.
Anyone driving in Iowa’s countryside might spot erratics on field edges where they were piled by farmers.
“Always ask the landowner for permission to collect, but farmers are often happy to get rid of them,” Anderson said. “Glacial erratics are at least one billion years old and some are two billion. Imagine having something so old.”
Perhaps the hardest Iowa rock to find to find, but most desired, is Lake Superior agate. This gorgeous, banded, usually small stone was formed far to the north and carried to Iowa by glaciers. As these vast ice rivers melted, they dropped their agates. Lucky folks find specimens along Iowa’s rivers, especially in the northeast corner of the state.
Iowa’s limestone bed is fossil rich.
“Probably the very best and legal place to collect them is at the Rockford Fossil and Prairie Park Preserve,” Houg said.
It’s managed by the Floyd County Conservation Board and is about one mile west of Rockford on county road B-47. Free collecting is encouraged. Visitors discover Devonian fossils, hike through prairies, enjoy the visitor center and see historic beehive kilns once used by the Rockford Brick and Tile Company. The site is open from sunrise to sunset, but may be seasonally closed. For information call ahead or check Floydcoia.org.
The renowned Devonian Fossil Gorge is in the Corridor’s center. Collecting is not permitted. The Army Corps of Engineers encourages visitors to walk, photograph and enjoy fossils. Leave them there. The nearby visitor center displays outstanding specimens. The town of Coralville and the big reservoir were named in honor of these magnificent fossils.
Collecting rocks is a fun hobby, but there’s plenty to do with them at home. Many people enjoy cutting and polishing rocks, or lapidary. The result is stunning jewelry or rocks to display on a bookshelf. Simpler polishing is done by tumbling smaller stones in a small rotating drum that gradually smooths and polishes them. It’s the same process waves use to polish beach stones, but it’s much faster.
“Tumbling is easier than cutting and polishing,” Desmarais said.
Iowa may lack the magnificent rocky topography of mountain states, but our state is blessed with a wide array of colorful and fascinating rocks that can be enjoyed inexpensively and easily.
Rich and Marion Patterson have backgrounds in environmental science and forestry. They co-own Winding Pathways, a consulting business that encourages people to “Create Wondrous Yards.”