Minnesota Clay

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Brick and Brick-Clay.

There are three main types or classes of clay that are suitable for brick, in the State of Minnesota :

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1. The ferruginous laminated clay of the loess-loam and river valleys.

2. The alkaline laminated clay of the loess loam and river valleys.

3. The Cretaceous alkaline clays.

There are places where the first and second are somewhat mixed, when their product, on being burnt for brick, may be made to vary much in character, color and quality by the length and manner of burning, but in general these clays are quite marked and distinct not only in the manner and locality of occurrence, but in the nature of the brick they produce. The hardpan clay is generally unfit for brick in Minnesota because of its being mixed with stones of all sizes, many of which are limestone and cause the brick to break on the slacking of the lime, either before or after they are put in the wall.

These three clays may be most easily discussed by stating first their origin and distribution. The first two are alluvial drift clays, and their nature depends on the character of the hardpan, or till, drained by the waters that deposited them. The drift (hardpan) came to the State of Minnesota from two sources, and from two directions. One, the earlier, came from the northeast, and is red, owing its origin to the ferruginous shales and clays of the Potsdam about Lake Superior, and to the decay of the ferruginous and igneous rocks of that district. This drift is scattered over the eastern and northeastern part of the State. Of course streams running from this area will, in high water, distribute along their banks, and over their flood-plains a red, ferruginous laminated clay, both in glacial and post-glacial times. The loessloam, wherever it prevails in that part of the State, partakes of this character and produces red brick. The other direction from which the hardpan clay came was from the northwest. This drift covers the larger part of the State. It is derived from the disintegration and distribution of the alkaline shales and clays of the Cretaceous strata, very largely, as well as from the limestones in the Red river, region. Hence we find that the surface water that drains this hardpan is alkaline, and of course the laminated clay that is found along such streams, both in glacial and in postglacial times, will partake of the nature of the original source, or will be alkaline. This general grouping, therefore, can be made: Streams flowing from the northwest in the northern and central portions of the State will furnish a laminated clay that will ex-

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hibit the qualities of the alkaline brick, and all others will exhibit the ferruginous qualities. There are but slight variations from this general statement. The Upper Mississippi drains an alkaline clay region. A clay used for brick near Brainerd is alkaline and furnishes a cream-colored brick. The bricks made in the Red river valley are cream-colored. Those made from the interglacial clays of the Minnesota valley are cream-colored, and exhibit most perfectly the application of the general principle stated.. Those made in the Minnesota valley from the alluvium of the present river are not so uniformly cream-colored, but are more frequently red. It seems as if the alkaline quality of the clays is not rapidly carried away now in the waters of this river, but that owing to a heavy coating of rich soil and the consequent protection of the alkaline hardpan clay from the surface drainage, the water does not come into contact with it freely. It is probable, also, that so much of the accessible soluble alkalies of the hardpan have been carried away that the water that now comes over it only receives from it such amounts of lime and iron as it can take up in passing, and that hence the recent alluvium does not fully illustrate the general principle stated. Wells sunk into this hardpan clay, however, in places unaffected by drainage courses, uniformly afford a water more or less alkaline.

The Cretaceous alkaline clay is a marine formation. It is sometimes calcareous, and even changed to limestone largely as in the Niobrara epoch, seen at New Ulm, and sometimes it is arenaceous, as well as carbonaceous. When Sufficient carbon accumulated it formed impure lignites, as on the Cottonwood river, and at Redwood Falls; and in some cases the deposit was completely changed from clay to sand, as in the Dakota epoch, or to a pure lignite valuable for fuel, as in some of the lignite beds of the Fort Benton. epoch. But by far the greatest part of the Cretaceous beds consists of alkaline shale or clay. It is this which, distributed through the hardpan clay, or till, gives it its marked characters, and which causes the alkaline laminated clays that give the cream-colored bricks of the Northwest.

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The question now naturally arises, how this alkaline quality aids in producing cream-colored brick, especially since on analysis these clays are found to contain iron as well as the red brick clays, and sometimes as much iron as the red brick clays. This question was answered by Mr. E. T. Sweet of the Geological Surrey of Wisconsin. In the presence of alkalies, silica is fusible and soluble at lower temperatures than without it. In the burning of the brick the sand, or silica, is fused, and combines chemically with the alkaline ingredients, and the iron present as red peroxide is fused also, and combines with them, making what we see—a cream-colored, ferruginous silicate of the alkalies and alumina. In this case the color of the iron as peroxide is lost in the mass. In the other class of clays, containing no alkalies, the silica and iron do not thus combine, and the color of the peroxide of iron is only intensified by the burning. In those cases where the iron is not wholly taken up the bricks are partially red, or are mottled with red and yellow.

The State of Minnesota is abundantly supplied with brick-clay. The valleys of the Minnesota and Mississippi rivers show at numerous places a very fine clay of inter-glacial age which supplies a cream-colored brick. Such are worked at Brainerd, at Minneapolis, at Carver, Chaska, Jordan. This same clay exists at St. Paul, and is seen in the gravel and drift bluffs where they have been largely excavated between Sibley and Wacouta streets on Fifth street, sometimes reaching sixteen feet in thickness. The brick made in the Red river valley are from an alkaline clay, probably of later date than that employed in the Minnesota and Mississippi valleys, and are, so far as known, of a cream-color; but this industry is not much developed in the Red river valley because of the scarcity of fuel. It would be much better, however, for that section to import wood from the Leaf Hills country, which is near, and use its own brick clay, than to import brick as is now done, from long distances. Large kilns, however, are run at Moorhead.

The bricks manufactured from the recent alluvium of most of the streams in the State, and from the red laminated clays of higher levels in the eastern part, are red. Such brick are made at St. Paul, Mankato, Belle Plaine, Henderson, and in many places in Fillmore, Houston, Olmsted, Goodhue, Wabasha and other counties.

So far as this industry is known at present through the available observations of the Survey, the bricks made in the State may

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be classified as follows. A great many observations have been made on brick burned in the northwestern part of the State, that cannot now be tabulated, also in Goodhue, Wabasha and Dakota counties.

Red brick are made at the following places: Alexandria, Hutchinson, St. Peter, New Ulm, Belle Plaine, Henderson, Shakopee, Redwood Falls, Parkers Prairie (Otter Tail county,) Cokato, St. Paul, Albert Lea, LeRoy, Austin, Forestville, Preston, Lanesboro, Chatfield, Kushford, Rochester, Oronoco, Eyota, Pleasant Grove, Byron, Dodge Center, Kasson, Mantorville, Owatonna, Blooming Prairie, Caledonia, LaCrescent, Spring Grove, Money Creek, Lake Calhoun (near Minneapolis,) White Bear (Ramsey county,) Faribault, Prairieville, Northfield, and New London in Kandiyohi county.

Very light red, or pinkish brick, resembling in color the Kasota building-stone, are made at Litchfield and at Evansville, Douglas county; and at Cokato, in Wright county, some of the brick are of a very dark red color, or brownish-red.

Cream-colored or yellowish bricks are made at the following places, generally in large quantities: Chaska, Carver, Jordan, Otsego (Wright county), Glenwood (Pope county,) Fergus Falls, Moorhead, Minneapolis, Brainerd, Shingle Creek, Frankford, Mower county, (some are also red;) Dayton, and Evansville, Douglas county.

A dirty drab or ash-colored brick is made at the following points: Detroit, Henderson, LeSueur; Sec. 2, Lake Mary, Douglas county, and at New Ulm.

The fire-brick of New Ulm is of a color much like the last, but lighter and harder, and speckled with iron. The Terra Cotta clay, formerly employed at Red Wing, is inter glacial clay found in the higher terrace plain of Hay Creek, near Red Wing, and actually then within the valley of the Mississippi. It corresponds to the brick clay of Carver and Minneapolis, the peculiar product known as terra cotta being due to the manner of treatment. The same manufacturer has more lately resorted to the potter’s clay used by the Red Wing Pottery Company, taken from Sec. 2 in Goodhue, Goodhue county.

The Cretaceous strata themselves are often useful for pottery. Establishments that employ this clay are located at Red Wing, Mankato and New Ulm. From this clay could perhaps be made a very superior red or brown pressed brick, but ordinary treatment will produce a light-colored brick. Yet the color and char-

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acter of the bricks made from any clay may be made to vary very widely by the admixture of other ingredients, and by a variation in the manner of burning.

The Cretaceous clays of the State, while making a superior quality of brick for building, are probably susceptible of much more extended uses. The experience of Mr. Winkelmann at New Ulm in the manufacture of fire-brick, and of several pottery establishments in the State, indicates that these clays are sometimes more refractory than is implied in the making of cream-colored bricks. In other words, the chief ingredients in some strata seem to be largely alumina and silica. These clays have not been chemically examined by the Survey, and no positive statements can be made as to their adaptation to these other uses. They are of the same age as the New Jersey plastic clays, which are used for making pottery and all refractory materials, as well as bricks for building, and terra cotta for ornamentation.

Brick is one of the best building materials, as it is one of the most common. It is lighter than most building-stone. It is convenient to handle in construction, and makes a very strong and durable wall. It resists fire better than any building-stone, not excepting granite. Its resistance to pressure of course depends on the quality. A poor, red brick will sustain but six or seven hundred pounds per square inch, but a brick of good quality will sustain from one to two thousand pounds per square inch, and one of the first quality, burnt hard, will endure between four and five thousand pounds per square inch. Sandstone ranges between three and five thousand pounds per square inch, and granular limestone between four and five thousand, some reaching ten and twelve thousand.


The Geological and Natural History Survey of Minnesota

The Eighth Annual Report, for the Year 1879

Submitted to the President of the University, February 18, 1880

Saint Paul: The Pioneer Press Company, 1880.

The Building Stones of Minnesota

W. H. Winchell, State Geologist

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