[Coon Creek] Page 115
The Minnesota Paving Brick Co. (Hydraulic Press Brick Co.) formerly had an extensive plant at Coon Creek, but this plant is now
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closed. The red drift is 40 feet or more thick and has been explored over 200 acres. The overburden is 20 feet of gray drift. (See Pl. XIII, A.) As dug from the ground the red drift contains some pebbles and boulders, which necessitate treatment by rolls or grinding machinery, but these are not as numerous as in the average of the red drift throughout the State. None of the pebbles are limestone except in the overlying gray drift, which is discarded because it is not available without cleaning. At the plant all the red clay dug is put through a double series of conical rolls by which many of the pebbles are removed and the rest crushed to a size that renders them practically harmless. A sample of the clay that had passed through these rolls slaked [quality by which a dry lump of clay tends to absorb water and fall to pieces when immersed] promptly and showed fairly high plasticity [capability of being molded], requiring 24 per cent of water for molding. Its shrinkage was 5 per cent and its tensile strength [maximum stress it can withstand before breaking] nearly 100 pounds to the square inch, though somewhat less if rapidly dried. The United States Bureau of Standards reports that the clay has fairly good vitrification [through intense heating, the clay particles fuse to a very hard, glass-like state] behavior, its porosity [ability to absorb fluids] being less than 5 per cent through a range of about 100° F. Enough organic matter is present to make the texture frothy and blebby if the clay is heated suddenly, but this is easily avoided by care at the plant. Burning tests resulted as follows:
| Cone No. | Color. | Shrinkage. | Absorption. |
| Per cent | Percent | ||
| 06 | Salmon | 2 | 17 |
| 05 | …do | 3 | 16 |
| 03 | Red | 5 | 10 |
| 02 | …do | 8 | 5 |
| 1 | Brown | 9 | 4 |
The following analyses were made by F. F. Grout on the clay as used at Coon Creek:
Analyses of red drift from Coon Creek.
| Chemical analysis. | Mechanical analysis. | ||
| Silica | 60.49 | Fine clay | 17.3 |
| Alumina | 12.62 | Coarse clay | 24.6 |
| Iron oxides | 7.80 | Silt | 47.5 |
| Magnesia | 3.68 | Fine sand | 5.1 |
| Lime | 3.87 | Coarse sand | 5.5 |
| Soda | 2.17 | ||
| Potash | 2.53 | ||
| Titanium oxide | 0.42 | ||
| Ignition | 5.90 | ||
| Moisture | 1.94 | ||
| 101.42 | 100.0 |
The Coon Creek company had a steam shovel and six large oblong downdraft kilns with a total capacity of about 40,000 brick a day.
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Its product was largely used by the Great Northern Railway in the construction of station buildings and paving station platforms. Some well-vitrified brick were roughened in imitation of klinker brick for fancy building material, and some were kept smooth for paving. At Minot [N.D.] a platform built partly with these brick and partly with the famous Purington brick from Galesburg, Ill., showed in practical service results very much in favor of the Coon Creek product. For harder use, as paving for city streets, the Coon Creek brick do not seem to have become as popular as they deserve. The city engineer of Minneapolis has tested them in comparison with the cobblestone paving produced in Minnesota and with the several types of paving brick now imported into the State. The average breaking load of Coon Creek brick was 16,000 pounds, the modulus of rupture was over 4,000 pounds, and the average crushing load was over 17,900 pounds, all three being greater than those of any other material tested. The percentage of absorption was zero. The percentage of abrasion was 7.18, which was as low as that of the best imported paving brick, though higher than that of the granite of St. Cloud. A sample of vitrified brick from the Coon Creek plant was purchased in the open market and shipped to Edward Orton, jr., of Columbus, Ohio, to be tested as paving material. He reports, “The brick did very well, and I think full-sized pavers of the same quality would have easily met the requirements of the American Society for Testing Materials.” The total loss after an hour in the rattler was 36.05 per cent. (See fig. 12.) The loss of the best grades of Illinois paving brick may be as low as 20 per cent on similar treatment; that of Iowa paving brick is 25 to 40 per cent.1
The high quality shown in all these tests indicates that the clays of the red drift of Minnesota are suitable for more extensive use. However, care must be used to select the less sandy deposits.
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