Knife River Flint

Some of you may have seen the news recently that the Lynch Quarry is now officially a National Historic Landmark. Most North Dakotans know about Knife River flint, but I suspect relatively few among us have actually seen the quarries near Knife River and Spring Creek in Dunn and Mercer Counties. With the National Historical Landmark status, a good portion of these Knife River flint quarries will now be preserved for future generations.

Flint, of course was the prized material Native Americans used for making arrowheads, spear points, and other tools and an all important piece of the old flintlock muskets. Knife River flint was not the only source of flint in the United States.

Flint was quarried in Texas, Ohio, and Missouri, for example. But Knife River flint was regionally quite significant. Archeologists estimate that the quarrying of Knife Rive flint dates back 11,000 years or more.

Around 30 quarries have been documented in Dunn and Mercer Counties in the area around Knife River and Spring Creek. Collectively there is something like 2500 pits or round depressions about 3-4 feet deep and 20 feet in diameter from which flint has been removed. Perhaps as much as a million cubic feet of flint has been removed from these quarries. That is a lot! It is roughly equivalent to removing a foot of earth from 23 acres.

So just what is flint: A fine-grained, very hard, siliceous rock. It may also be defined as a fine grained form of quartz. Knife River flint is siliceous lignite that is generally root beer or coffee colored. The dark color is thought to be due to tiny bits of organic matter.

Perhaps like you, I initially thought that, for some reason, there was a massive block of flint underlying the area around the Knife River. That is not the case, however. What was mined were flint rocks of various sizes lying on and near the soil surface. So the flint quarries are in what geologist call the secondary source of the flint. The primary or original source of the flint is though to have been eroded away. What was left in this area near the Knife River at the end of the ice age was a flint littered landscape.

Chuck Lura

Natural North Dakota is supported by NDSU Central Grasslands Research Extension Center and Minot State University-Bottineau, and by the members of Prairie Public. Thanks to Sunny 101.9 in Bottineau for their recording services.