Imagine that you are trekking across Central Nebraska in the Miocene Epoch, about 6-10 million years ago. There are no highways, no towns, no people… just seemingly endless grassland crossed by pristine rivers and dotted with small patches of woodland. The climate is pleasant and hardly ever cold. Elephants, rhinos, camels, horses, and tapirs still roam the area, and there might be a saber-toothed catlike predator lurking nearby. Near future Scotia, Nebraska, you are surprised to see a large lake—a very inviting place for animals of all kinds. That lake is depositing layers of sediment consisting of billions of tiny, algae-like organisms called diatoms. They grow abundantly as the ancient sunlight filters down through the cool, clear waters.
The Happy Jack Chalk Mine is one of the most unusual and interesting sites of geological interest on the Great Plains. The “chalk” is not chalk at all, but rather a soft rock called diatomite that contains abundant calcium carbonate, the same chemical compound that makes up limestones. The term diatomite refers to those billions of diatoms that lived in that ancient lake millions of years ago.
As you tour the mine today, you are literally walking through the bed of an ancient lake. But there is more to the mine than that. Sometime after the lake filled with sediment and the local water table fell, the site was part Miocene grassland on the board river floodplain. Rodents like modern prairie dogs and pocket gophers burrowed down into the old lake sediments and built spacious nests in which multiple generations of offspring were born and reared. These ancient rodents left the marks of their teeth in the dozens of burrows that are now visible in the mine’s walls. In fact, the mine is probably one of the best places in the world for seeing well-preserved ancient mammal burrows.
And what about the mine itself: An Army explorer had first seen the “chalk” in the 1850s, and by 1877 local residents had begun to mine the strange lightweight rock. Originally, the “chalk” was used as structural stone in buildings, and one “chalk” building still survives in Scotia, Nebraska. In the 20th century, however, interest turned to mining the rock for other purposes, particularly as filler in paints. From the 1930s to the end of World War ll, the “chalk” was mined underground using simple tools and an old Ford Model “A” transformed into a makeshift dump truck. The “chalk,” today known by the more accurate from “calcareous diatomite” was loaded by hand into boxcars and shipped to Omaha for processing. For many years after its closure, the mine stood abandoned. It was an undeveloped wayside area for a time, but closed in 1983. Only after the Happy Jack Chalk Mine Association renovated the mine and added lighting in 1997 was the full story of the mine’s geology and human history accessible to the general public.
The Happy Jack Chalk Mine is one of the only two underground diatomite mines known to have existed in the United States, and the only one that is open to the public. Touring the mine is a truly memorable experience. From Miocene lakes and grasslands, to the production of a once-valuable mineral commodity, the mine illustrates the interconnectedness of people, our environment, and the Earth’s distant past.
Compiled By: Matt Joeckel and Shane Tucker
Today, the mine offers public tours that are both educational and exciting. Happy Jack Chalk Mine is located near Scotia, Nebraska and also includes free hiking trails, picnic areas, scenic views, bird watching and over 150 varieties of native plant life.