Geology Meets Mathematics at Altgeld Hall
Built in 1897, Altgeld Hall was constructed of Kettle River Sandstone, quarried in the appropriately-named town of Sandstone MN. This rock is a medium-grained sandstone (98% quartz) of Precambrian age (very old). The sand grains are held together with a silica cement, creating a strong stone that can be used for curbing, bridges, dams, and foundations, as well as buildings.
“In color it is a light salmon, giving it a warmth and beauty possessed by very few stones native to this country.” (Johnson, 1899). Black lines on the stone are lichens, but if you examine a clean surface, you may be able to see round grains of sand forming layers within a single block.
On both large blocks below the center of the left photo, you can see slanted lines of bedding in the sandstone. The carvings on top are heavily overgrown with lichens. Although these stones are at the top of the building, it is possible to find similar surfaces at ground level.
The main entrance to Altgeld Hall is located on the north side of the building. Trees and other structures nearby block the summer sun so that it hardly ever shines on this wall, and the main entrance is usually shaded.
Further geological information about the Kettle River Sandstone:
- Now called the Hinckley Sandstone
- Part of the Keewanawan Supergroup
Sources
- Grout & Brodrick, 1919, The Magnetite Deposits of the eastern Mesabi Range, Minnesota
- Johnson, 1899, Kettle River Sandstone
- UIHistories Image IDs 17643, 17623, and 21292
Image selection and text by Eileen A. Herrstrom 2014