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The most valuable deposit of the laminated clays seems to be one on Sauk Lake, most easily reached from Sauk Center, in Stearns County, 3 or 4 miles to the south. The clay bank rises steeply from the shore of the lake to a height of 15 or 20 feet and extends several rods back under the level surface. The clay directly underlies the soil, although in some places its upper beds are sandy. Pits have
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been opened at numerous points along the shore, exposing sections that vary considerably. Limy concretions occur in a few places. The best clay which is reported to lie at water level is gray in color, and the main part of the bank above water level is yellowish white. Upham1 concluded that this clay accumulated in a channel in the melting ice sheet while a large mass of ice still occupied the basin of Sauk Lake. Products made from the different parts of the bank include both red and cream-colored brick, hollow brick, terra cotta, and flower pots. Samples of the yellow and gray clays show the usual differences. The average air shrinkage is 3.5 per cent, but that of the blue clay is 5.5 per cent. An average mixture of the material in the bank was burned at the Minnesota School of Mines experiment station, with the following results:
| Cone No. | Color. | Shrinkage. | Absorption. |
| Per cent | Per cent | ||
| 05 | Salmon | 0 | 21 |
| 02 | …do | 1 | 22 |
| 2 | Buff | 5 | 14 |
| 3 | …do | … | … |
The clay is hard after burning to cone 02 (2,030° F.) and reaches viscosity [change in form] at cone 3 (2,174° F.), having thus about the same range as the average gray laminated clay in other parts of Minnesota. Selected samples from different parts of the deposit differed in plasticity [capability of being molded] but were almost identical in their behavior in the fire. Mr. David Pangburn, who has taken the lead in developing the deposits and in experimenting with them, has retired, and active work on the deposit has been dropped; but plans are in progress for a reorganization, and it is thought that, in view of the amount of good clay available, shipping facilities will be provided and excellent products will be turned out.
Source:
Clays and Shales of Minnesota
By Frank F. Grout
With Contributions by E. K. Soper
United States Geological Survey, Bulletin 678
Washington, Government Printing Office, 1919