Hamline News

Stone Work in the Lab


For some students, summer means swimming in a lake or combating the heat in the comfort of an air-conditioned room. You could say professor Brian Hoffman and students Delaney Grundhauser and John Seidl got to experience both thanks to one thing: Prairie du Chien chert.

As part of ongoing research over the last few years, Hamline’s anthropology field school has been exploring Louisville Swamp Unit, a site nestled in Shakopee, Minnesota. Part of the greater Minnesota Valley National Wildlife Refuge, Louisville is known as one of the more ecologically diverse areas in the state. Historical evidence of human occupation dating back to 10,000 years has been documented there.

Enter Prairie du Chien (PDC) chert. Chert is a type of rock that can be used for flint knapping, an ancient technology to create stone tools. To create these tools, the chert is struck by a hammer to create the desired shape, often flake or chip-like stones. These flakes are not in short supply at the Louisville site and are the main focus of summer collaborative research for Grundhauser and Seidl.

“When I first started, I did a lot of reading before doing the actual research,” Junior Delaney Grundhauser explained. Her research project is based in experimental archaeology, a methodology of replicating ancient technologies to get similar results or changing variables to better understand the material through a scientific viewpoint and historical viewpoint. Her readings helped her better understand these perspectives.

Once her reading was complete, Grundhauser spent her days hammering raw PDC in the basement of Drew Science Hall to create flakes similar to those of the past. She then compared these flakes to the original ones collected at the site. The neat rows and rows of flakes on her lab table show the fruits of her labor. With Grundhauser’s work, the team can learn the process used by the original occupants of the Louisville Swamp.

Senior John Seidl sat at a lab bench nearby and answered a different experimental question regarding the chert: what does heat do to the rock? Heating plays a crucial part in flint knapping as it aids in the creation of quality stone tools; however, there is little understanding and previous knowledge of how various PDC chert reacts to heat treatment. In order to gather the data, Seidl placed samples on a dish and heated them to 500 degrees and then heated another set to 1000 degrees in an oven lent by the Minnesota Historical Society. He then noted the difference in quality, color, and luster of PDC at the different temperatures.

Seidl explains it was “very much like baking.” Except this was a cake that can take up to 9 hours to complete. When heating up rocks, the process can take up to four hours and the cooling can take another five to ensure fracturing doesn’t occur. With his research, archaeologists can begin to understand how ancient people of Louisville fashioned their tools. Seidl noted while conditions may possibly have never been thousands of degrees, it adds body to the knowledge that is known about this material.

The ultimate goal of the project is understanding people of the site’s past. “We are able to see the economic and social landscape of Minnesota through the rocks,” Professor Hoffman said.

It certainly was a job that took patience, but for these three, it made for an exciting summer from muggy swamps to cool lab rooms. 

“There are some interesting things you can learn from looking at rocks for eight hours a day,” Grundhauser said with a grin.

Written by Malenie Ven