Page 189. Clays. The blue and yellow, non-fossiliferous clays at the base of the Lime Creek shales are widely distributed in Cerro Gordo county and furnish inexhaustible amounts of material for use in the manufacture of clay goods of a great variety of kinds. For some purposes, as the manufacture of common structural brick, certain parts of the Iowa drift clays comparatively free from pebbles, will be found available. The drift clays of the Wisconsin stage contain so many limestone pebbles as to render them unfit for use in the manufacture of any products.
Mason City Brick and Tile Co. – At present clay goods are made at only one point in the county. The Mason City Brick and Tile Co. have an extensive plant (Fig. 23) (shown in pictures section) in the southwestern part of Mason City. The clay used comes from the unfossiliferous portion of the Lime Creek formation. In the clay pit, which is just north of the factory, the beds exposed embrace twelve feet of blue shales overlain by twelve feet of yellow shales, with twelve to fifteen feet of blue shales known to exist below the bottom of the pit. The plant embraces the main factory building; steam heated drying sheds; an office building; six round, down-draft kilns; two
Page 190. up-draft kilns; a Sioux City Corliss engine of 125 horse power; two eight horse power boilers; a Madden & Co. machine with a capacity of 25,000 bricks daily; and the necessary hoists, tail ropes, tramways, cars, pallets, etc., for handling the ware in the various stages of manufacture. The product of the factory includes.
1. End cut structural brick.
2. Hollow brick of the following dimensions:
a. 8x8x12 inches.
b. 4x8x12 inches.
c. 4x4x12 inches.
d. 4x8x10 inches.
e. 4x4x10 inches.
f. 8x8x8 inches.
g. 4x8x8 inches.
h. 4x4x8 inches.
i. 4x4x4 inches.
k. 2 1/4x4x8 inches.
3. Agricultural drain tile three and one-half to twelve inches in diameter.
4. Sidewalk tile 2x8x8 inches.
5. Window sills and caps.
Page 191. The clay burns to a light red color. The ware is very hard, ringing sharply under a gentle tap of the hammer, and is so compact as to be practically non-absorbent of water. Small crystals of selenite are diffused are diffused through the clay and cause a slight deposit of chalky looking powder on the surface of the ware in the process of the burning. For most of the product this is unobjectionable, but wherever it is desired to prevent its appearance, as in the case of face brick, it can be easily remedied by mixing a small amount of carbonate of baryta with the raw clay. An analysis of the blue clay in the lower part of the pit was made by Prof. G. E. Patrick, with the following results.
Hygroscopic water (expelled at 100° C.)…0.85 per cent.
Combined water (expelled by ignition)…3.74 per cent.
Carbonic acid, C O2…4.80 per cent.
Silica, Si O2…54.64 per cent.
Alumina, Al2 O2…14.62 per cent.
Iron oxide (calculated as Fe2 O2)…5.69 per cent.
Manganese oxide (calculated as Mn O)…0.76 per cent.
Lime, Ca O…5.16 per cent.
Magnesia, Mg O…2.90 per cent.
Soda, Na2 O…1.12 per cent.
Potash, K2 O…4.77 per cent.
Total…99.05 per cent.
Error in analysis…0.95 per cent.
Total…100.00 per cent.
The factory of this company is operated continuously throughout the year; twenty-seven men are employed, and the value of the annual output exceeds $30,000. The area in which the product of the factory finds a market has a radius of about 200 miles.
Nelson brickyard. – Some years ago a brick yard was operated about a mile north of Mason City. The clay used is a modified drift only about eight inches thick. This clay was tempered in the ordinary pug-mill, and the brick were made by hand. Temporary kilns were used for burning. No work has been done here, however, in recent years, and with
Page 192. abundant supplies of easily accessible clays in the Lime Creek shales, the drift clays of the county will not probably ever be in very great demand. It is from the beds of Devonian shales that the clay industries of the future, for this region, will get their supplies of raw material.
Future of clay industries. – In respect to clays Mason City has the same advantages as in the matter of building stone and lime-burning rock. The raw material is of the best quality, and the supplies are inexhaustible. The facilities for shipping the manufactured product are good. An extensive region throughout which the demand must yearly increase, and yet without available deposits for manufacturing to supply its own needs, begins practically at the western limits of the city. And so industries based on the geological resources of the county – quarrying, lime-burning, and clay working – are certain, under wise and enterprising management, to grown in importance with the growth of the great territory that must either get supplies from Mason City, or from more distant points involving longer haulage and higher rates of freight. (Iowa Geological Survey Annual Report, 1896, With Accompanying Papers, Volume VII, Samuel Calvin, State Geologist and A. G. Leonard, Assistant State Geologist, Iowa Geological Survey, Des Moines, 1897)