Shakopee Clay

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

[Shakopee]                                                     Page 230

At Shakopee the river alluvium is known to extend over 20 acres to the unusual depth of 30 feet.  A dark clay some distance from the river is more plastic than that closer by, and the two are mixed to produce material proper for soft-mud red bricks.  Some re-pressed brick are made at the same plant.  The [unfired] clay slakes [quality by which a dry lump of clay tends to absorb water and fall to pieces when immersed] in three minutes and has a rather low plasticity [capability of being molded].  It requires 23 per cent of water for molding and shrinks 4 per cent on drying.  Its tensile strength [maximum stress it can withstand before breaking] is about 150 pounds to the square inch and is not much reduced if the clay is rapidly dried.  Burning tests resulted as follows:

            Page 231

The clay becomes hard at cone 01 (2,066° F.) and reaches viscosity [change in form] at cone 4 (2,210° F.).  The plant has a capacity of about 3,000,000 brick a season.  Burning is conducted in a patent 30-arch kiln by what is known as the John G. Boss system.