Geodes on display at Wetlands Centre
By Audrey Posten with Phil Burgess
Area rock collector Phil Burgess, of Prairie du Chien, has been busy the past year amassing a collection of common Upper Midwest minerals and fossils for public display at the Driftless Area Wetlands Centre in Marquette. He has included such items as drusy quartz, stromatolites, agates, two-billion-year old iron formation and fossil coral from Wisconsin’s Door County. But one thing had been lacking—that is, until now—Iowa’s most famous rock, the geode. Now, the Wetlands Centre is in unique company.
“There’s no place in this part of the state that has these on display,” Burgess said of the geodes.
What is a geode? Geodes are hollow, spherical rocks filled with sparkly crystals. Clear quartz is the most common mineral, though over a dozen other minerals have been identified. Geodes occur in southeastern Iowa and adjacent states in Mississippian age (359 to 323 million years ago) shale and limestone formations. They are much-prized by collectors. In 1967, the geode was named Iowa’s state rock.
In March, Phil attended a rock and gem show at Hawkeye Downs in Cedar Rapids. By happenstance, a vendor there was offering a whole table full of choice geodes for sale. Burgess bought a monster 19-inch diameter specimen for himself, as well as a pail full of smaller specimens, which he donated to the Wetlands Centre. When Burgess mentioned that he was planning to place the specimens on public display, the vendor tossed in a big gem-like eight-inch geode for free.
Burgess said the larger geodes on display at the Wetlands Centre are more rare, with the smaller ones the most common size. From the outside, he said, a person cannot tell that the rock is a geode; it has to be broken open to expose the sparkling inside.
Burgess explained that geodes are frequently found in rock quarries. In parts of Iowa where they are plentiful, some people have set up businesses that allow enthusiasts to come in and dig for geodes.
“I haven’t dug myself, but it’s a really fun hobby,” Burgess said. “It’s a good family activity.”