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THE UNIVERSITY

OF ILLINOIS

LIBRARY

630.7
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A6RICULTURAL
UIBW



UNIVERSITY OF ILLINOIS

Agricultural Experiment Station



BULLETIN No. 232



I: POTASH SHALES OF ILLINOIS

II: GEOLOGY, DISTRIBUTION, AND OCCUR-
RENCE IN UNION COUNTY

III: FINELY-GROUND SHALE AS A SOURCE OF
POTASSIUM FOR SOIL IMPROVEMENT



A joint publication by the Division of
Applied Chemistry of the University of Illi-
nois; the Illinois Geological Survey; and
the Agricultural Experiment Station




URBANA, ILLINOIS, MARCH, 1921



CONTENTS OF BULLETIN No. 232

PART I: POTASH SHALES OF ILLINOIS PAGE

Introduction 229

Constitution of Illinois Potash Shales 231

Extraction and Concentration of the Potash 235

Conclusions . 235

PART II: GEOLOGY, DISTRIBUTION, AND OCCURRENCE OF THE
POTASH-BEARING SHALE OF UNION COUNTY

Introduction 237

Topography 237

Character of the Shale and Associated Rocks 238

Availability 241

Localities of Possible Commercial Importance 241

Localities Mainly of Local Importance 243

PART III: FINELY-GROUND SHALE AS A SOURCE OF POTASSIUM

FOR SOIL IMPROVEMENT . . 244



FOREWORD

Some five years ago Professor S. W. Parr, of the Division of
Applied Chemistry at the University of Illinois, began a 'somewhat
exhaustive study of Illinois shales as a source of oil, samples being
furnished by the State Geological Survey, and as in all such cases
gave careful attention to possible by-products. Most of the shales
examined proved poor in oil-bearing properties, but some of them were
surprisingly rich in potassium compounds.

Dr. Robert Stewart, of the Agronomy Department, in common with
other students of soil fertility, was at the same time interested in every
possible source of potassium available for agricultural purposes. Upon
being advised by Professor Parr of the promising character of Illinois
shales, he began at once experiments intended to show whether the par-
ticular potassium compounds present in these shales could be made
available for agricultural purposes.

The present publication consists of three parts : Part I, prepared
by Professor Parr and Mr. Austin, of the Division of Applied Chem-
istry, presents a brief account of the potassium-bearing quality of
these shales; Part II, prepared by Mr. Frank Krey, of the State
Geological Survey, gives the location and approximate extent of the
deposits; and Part III, prepared by Dr. Stewart, reports the pre-
liminary investigations into the agricultural side of the problem.

While further experimentation will be necessary to determine
whether these potassium compounds can be made available under field
conditions, enough has been done, not only to show the presence of
vast amounts of this valuable material in Illinois shales, but also to
demonstrate that the compounds are capable of reduction by agri-
cultural plants grown under laboratory conditions.

E. DAVENPORT




FIG. 1. EFFECT OF SHALE ON THE PRODUCTION OF CORN

The pots were filled with peaty soil to which was added the materials indicated.
The yield of corn fodder on the shale pots was twice that on the check pots. See
page 251 for further particulars concerning this experiment.



PART I

POTASH SHALES OF ILLINOIS

BY S. W. PARE, PROFESSOR OP APPLIED CHEMISTRY, AND
M. M. AUSTIN, ASSISTANT IN CHEMISTRY

During the years 1916 and 1917 certain Illinois shales were being
studied in the laboratory of applied chemistry at the University of
Illinois, with primary reference to the amount of oil they would
produce upon destructive distillation.

The shale from only one region, Johnson county, proved to be
sufficiently rich in oil (45 to 50 gallons per ton of shale) to be of
interest for its oil yield alone. Numerous other shales were found
giving from 15 to 20 gallons per ton, and hence of questionable value
from a consideration of their oil possibilities alone. This constituted,
therefore, a primary reason for examining all samples for other values,
such as phosphorus and potash. The samples were furnished thru the
courtesy of the Illinois State Geological Survey and came mainly from
the southern part of the state. Phosphorus, except in insignificant
amounts, was not found in any of the shales. Certain samples, how-
ever, gave a percentage of potash quite unexpected and quite unusual
for material of this type.

It is fairly well conceded by students of the potash situation in
this country, at least from the chemical viewpoint, that the most hope-
ful source for a domestic supply resides chiefly as a by-product from
the manufacture of cement. The shale or other siliceous material that
enters into the raw mix for cement-making always carries a certain
percentage of potash. In the process of burning the clinker, this
potash assumes the volatile form ; hence it may be recovered by simple
methods of condensation and leaching. Even tho the average shale as
used in the cement mix does not contain, on the average, more than
from 1.5 to 2.5 percent of potash (K 2 0), still the potential supply
from this source, in the aggregate, would be very great.

The Illinois shales that we are here considering, instead of having
an average potash content of 2 or even 21/2 percent, have a content of
5 percent, in the raw state. They compare, therefore, very favorably
with the green sands of New Jersey, concerning which not a little
consideration is now being given both in the literature and financially,
as a possible source of supply for this important product. 1 The first

1 Chem. and Met. Eng., 22, 815. 1920.

229



230



BULLETIN No. 232



[March,



question that naturally arises, therefore, relates to the suitability of"
these Illinois shales with reference to their main constituents for the
purpose of compounding into a suitable cement -mix. The best
authority on this phase of the topic is Professor A. V. Bleininger, who
in his study of Illinois shales for cement-making, 1 gives analyses for
eight samples which he deems suitable for such a purpose.

They show so little variation in composition that for purposes of
illustration in this discussion they may be fairly represented by an
average value for each constituent. These values are given in the
second column of Table 1. For comparison, therefore, as to their
suitability along cement lines, two of the high-potash shales are shown
in parallel columns 3 and 4.

TABLE 1. COMPARISON OF ILLINOIS SHALE CONSTITUENTS WITH REFERENCE
TO THEIR CEMENT-MAKING PROPERTIES





Average of eight
Illinois shales
(Bleininger)


Sample No. 1
Illinois potash
shales


Sample No. 2
Illinois potash
shales


SiO, .


61 56


53.8


55.0


Al.O, .


16 12


17 7


163


Fe,O, .


296


58 1


60 1


Fe O


3 52






CaO


094


7


0.3


MgO ..


1 79


1.8


1.5


K 2 O


2.90


5.0


4.9


Na 2 O


0.82


0.5


0.4


Ignition loss


6.72


11.9


13.0



1 Total iron calculated to Fe 2 O,.

Probably the most characteristic feature of this table from the
cement-making standpoint is the ratio between the silica (Si0 2 ) and
the alumina (A1 2 3 ). According to the average American practice,
this ratio should fall between 2.5 and 3.5. Upon calculating these
ratios for shale samples Nos. 1 and 2 of the table, we have :



Shale No. 1
Shale No. 2



53.8
17.7
55.0



= 3.02
= 3.37



Hence, it is evident that on the basis of the silica-alumina ratio
the two samples of the potash shales under consideration are seen to
be in the most advantageous zone.

Since, in the process of compounding to produce a suitable cement
clinker, a shale is mixed with from two to three times its weight of
limestone, it follows that the percentage of K 2 in the raw mix is
correspondingly reduced. In the average American practice this fac-
tor amounts to from 0.7 to 1.0 percent, and on this basis with a 66%

'111. State Geol. Survey Bui. 17, p. 101. 1912.



19i!l] PART I: POTASH SHALES OF ILLINOIS 231

percent recovery of the total potash there would result an average
yield of about 2.9 pounds of K 2 per barrel of cement made. On the
same basis the potash shales as given in columns 3 and 4 of Table 1
should show a yield of 5.4 pounds per barrel.

On this basis, estimating the price of potash at 15 cents per pound,
the shales here studied would return a value for the potash recovery
alone of 82 cents per barrel of cement made, as against 19% cents
recovery from the average potash content of the ordinary raw
cement mix.

Reference thus far has been made only to the shale values from
Union county in southern Illinois. But one other region in the state
has thus far supplied a shale with a high potash content. This has
come from the neighborhood of Dixon, in Lee county. This shale
shows a potash content in the raw state of 5.8 percent. It is coarse-
grained, friable, and while of a green color suggestive of the eastern
green sand, the geological character of the material is quite different.

CONSTITUTION OF ILLINOIS POTASH SHALES

The shales from Union county are peculiar in that they have a
small percentage of oil which is present in the free state. This has no
industrial significance, but being volatile it adds to the other volatile
constituents, such as water of hydration, so that upon ignition the
reduction in weight, as shown in Table 1, amounts "to about 12y 2
percent of the raw material ; hence upon ignition the potash content
of the residue is seen to be 5.75 percent. With the Dixon shale but
little loss on ignition occurs (see Table 3) ; hence the potash percentage
remains about the same in either the ignited or the raw state.

For determining the form of combination in which the potash is
held, no very simple or direct method is available. One procedure con-
sists in digesting one gram of the sample with 25 cc. of concentrated
sulfuric acid, heating the same until about half of the acid has been
removed, diluting, filtering, washing, and igniting the residue, and
analyzing it for total potash. The percentage of potash lost is con-
sidered as being in some other than the feldspathic form.

By this procedure 62 percent of the total potash was found to be
removed from the Union county shales, while from the Dixon shale
only about 15 percent was removed. This shows a marked difference
in the chemical composition of the two shales. Further proof of this
difference was desired. It is true that in the process of cement manu-
facture the potash would be equally recoverable in either case ; never-
theless, from any other standpoint, differences in the ease with which
the potash might be removed by chemical solvents or concentrated into
a form for more ready extraction, might make a wide difference in the
value of the' shales from the two sources.

It is not the purpose of this discussion to go into the details of the
experiments to determine the chemical character of the potash-bearing



232 BULLETIN No. 232 [March,

constituents. The method of analysis just described suggests that the
potash in the Dixon shale is chiefly or altogether feldspathic in com-
bination, and that the major part, at least of the potash in the Union
county shale, is in some combination more nearly resembling the
glauconitic or green-sand formations. These formations are considered
as being potassium iron silicates with an average potash content vary-
ing from 5 to 7 percent K 2 0.

With the marked difference in type suggested by the analytical
results obtained from the use of concentrated sulfuric acid, it seemed
worth while to prepare thin sections for study under the microscope.
No very positive information came from such studies. In general it
seemed evident that the Union county shales had passed thru extensive
secondary decompositions and that the Dixon shales had not. Both
types however, even in the undisturbed condition of the deposits, had
their ultimate particles in such a finely divided state as to render
impossible their resolution and study under the microscope.

A third method of study into the probable type of composition
suggested itself as follows:

Accepting the generally conceded fact that potash in feldspathic
combination is but very little, if at all, directly available as plant food,
it might afford further data on composition if experiments were
inaugurated to determine whether the Union county shales contained
some of their potash in a form which was directly available for plant
use. Some foundation for this theory was already afforded by the
fact that 62 percent of the total potash in those shales, as already
determined by analysis, was soluble in acid; thus furnishing a start-
ing point in the evidence as to their difference from feldspathic
material. Moreover, if the Union county shales responded to plant
requirements and the Dixon shales did not, the evidence would pro-
ceed one step further. And again, if the Union county shales were
treated with strong acid in such a manner as to remove all their acid-
soluble potash, and if, after being freed from acid, the residue with the
remaining 38 percent of potash (presumably in feldspathic combina-
tion) was submitted to plant action and was found lacking in avail-
able potash, this would afford a still further proof in the chain of evi-
dence as to the type of potash combination in the original shale.

Fortunately at this stage of the chemical studies, upon appealing
to the Agronomy Department of the College of Agriculture for help
in conducting the necessary pot cultures, it was found that such a
procedure fitted in well with a program of their own concerning
studies on the availability of potash as plant food, in a series of natural
substances; hence the potash shales in hand would furnish an addi-
tional type of material.

It is not the purpose in this part of the discussion to go into the
details of the results from these pot cultures further than to correlate



1921]



PART I: POTASH SHALES OF ILLINOIS



233



the results in so far as they have a bearing upon the shale composition
as already set forth.

In Table 2, therefore, an attempt is made to show the behavior of
the various shale materials applied to a peat soil deficient in potash.
Buckwheat was selected as the plant most responsive to the varying
treatments. An equivalent quantity of potash was added in each
case, except of course, to the check pot, which being used for compari-
son was without addition of potash in any form. Each pot was made
up of 7 kilos of peat soil, 60 grams of pulverized limestone, and the
various types of shale material ground to pass a 100-mesh sieve and
in an amount that would carry into the soil mixture in each case a
total potash content of 1.34 grams.

TABLE No. 2. COMPARATIVE STUDY OF PLANT GROWTH (BUCKWHEAT) USING
SHALE MATERIALS OF DIFFERENT COMPOSITION



DESCRIPTION OF POTS


CONDITION OF PLANTS Six WEEKS
AFTER PLANTING


No. 1
Check pot using peat soil with in-
sufficient potash


Poor growth


No. 2
Peat soil as in No. 1, with Dixon
shale


Poor growth, not distinguished from
No. 1


No. 3
Peat soil as in No. 1, with Union
county shale, less 62 percent of
potash by acid extraction


Poor growth, not different from Nos.
1 and 2


No. 4
Peat soil as in No. 1, with Union
county shale ignited


Excellent growth more dense and taller
than Nos. 1, 2, or 3


No. 5
Peat soil as in No. 1, with Union
county shale, sample No. 1 not
ignited


Excellent growth, not distinguishable
in density or vigor from No. 4


No. 6
Peat soil as in No. 1, with Union
county shale, sample No. 2 not
ignited


Excellent growth, equal in every re-
spect to Nos. 4 and 5



This amount of potash represents the weight per acre that would
be present in a normal soil which was deemed to have an adequate
supply of that constituent. The results as presented in the table are
also very clearly shown in the photographic reproduction.

Pot No. 1 is the check, with deficient potash. No. 2 has
the standard equivalent of 1.34 grams of K 2 added in the form
present in the Dixon shale, and No. 3 has the same addition in the
form of acid-insoluble residue from the Union county shale. An exam-



234



BULLETIN No. 232



[March,



ination of these three pots seems to warrant the conclusion that potash
in any available form is lacking in each case. This, therefore, would
seem to confirm the previous assumption that the potash present in
Pots 2 and 3 is in the f eldspathic form.




FIG. 2. BUCKWHEAT PLANTS GROWING ON PEAT SOIL TO WHICH VARIOUS
SHALE MATERIALS HAVE BEEN ADDED



1
Check



2

Dixon
Shale



Union Co.
Acid ex-
tracted



Union Co.
Ignited



Union Co.

No. 1. Not

ignited



6

Union Co.

No. 2. Not

ignited



By further reference to Pots 4, 5, and 6, there is an equally obvious
indication that in these pots there is potash present in a form available
for plant use; and since the only variable in the experiment is the
acid-soluble constituent, it is evident that the potash utilized by the
plant comes from this source.

Moreover, ignition or non-ignition of the shale does not affect the
property of the potash so far as food availability is concerned. It
would be of scientific interest, of course, to be able to say more
definitely what was the form of potash combination here found. We
have compared it thus far in the discussion to the green sands of the
eastern United States, which are true glauconites. The most that can
be said of these shales is that they are glauconitic in type. They may
have been originally a feldspathic deposition which has undergone
secondary decomposition in situ. Indeed, the region has other striking
examples of secondary decomposition products resulting from similar
methods of decomposition; for example, the very pure deposits of



3921] PART I: POTASH SHALES OF ILLINOIS 235

amorphous silica, found so abundantly in Union county. So far as
conformity to green-sand or glauconitic conditions is concerned, there
is every justification for such a classification, as may be seen from the
following quotation, 1 indicating the geological conditions under which
the true glauconites are supposed to have been formed :

' ' The organic matter transforms the iron into sulfid which may be oxidized
to hydrate, sulfur being at the same time liberated. This sulfur would oxidize
to sulf uric acid, which would decompose clay, setting free colloidal silica, aluminum
being removed in solution. Thus, we have colloidal silica and hydrated iron in
a state most suitable for their combination. The potash which is necessary to
complete the composition of glauconite may be derived from the decomposed
fragments of crystaline rocks like orthoclase or white mica."

Upon analysis of the shale for iron in the pyritic form by methods
developed in this laboratory, 2 it appears that when the pyritic iron
is deducted from the total iron of the shale there remains 3.8 percent
of iron available for combination with the 3.1 percent of potash pres-
ent in the acid-soluble form, an amount which approaches the ratio for
glauconitic material with sufficient approximation to warrant the
classification thus proposed ; viz., not true glauconite but glauconitic
in type.



EXTRACTION AND CONCENTRATION OF THE POTASH

It is perhaps sufficiently evident from the preceding description
of the composition of all these shales that no practical method for the
extraction of the potash on an industrial basis is possible. This con-
dition, however, does not preclude the method of extraction by way
of the cement-making process. In any case where the by-products
have values, such a combination process may come within the range
of industrial possibility. It is not considered essential to this dis-
cussion to give the details of the experiments directed toward extrac-
tion or solution methods for direct recovery of the potash. While
practicable as a laboratory procedure, they would not be profitable as
industrial processes.

CONCLUSIONS

1. Shales occur in at least two localities in Illinois, which contain 5 percent
or more of potash.

2. Shale outcropping in several places near Jonesboro, in Union county,
which contains 5 percent of potash would be suitable, so far as can be determined
from its chemical composition and physical character, for use in the manufacture
of Portland cement.



'Clarke, W. B., Jour, of Geol., 13, p. 509. 1900.

^Powell, A. B., with Parr, S. W., Univ. 111. Eng. Exp. Sta. Bui. No. 111. 1919



236



BULLETIN No. 232



[March,



3. By using this material in the manufacture of cement and by applying
the known methods of potash recovery, a yield of 5.3 pounds of potash, repre-
senting a value of 70 to 80 cents per barrel of cement, could be obtained.

4. The constitution of the southern Illinois shale is complex. The shale
contains free oil, bituminous matter, pyrite, undecomposed potassium-bearing rock,
feldspathic in character, and potassium-bearing material of the nature of glau-
conite or green sand.

5. Shale from Dixon, Lee county, contains 5.8 percent of potash, which is
held for the most part in a more stable condition than that in the southern
Illinois shale.

6. Extraction of the potassium from shale of either the southern Illinois
or the Dixon type by means of solid or liquid reagents would seem to be im-
practicable, because of the cost of leaching and recovering potash from material
where it is present in such small amounts.

7. The plant availability of the potash in the southern Illinois shale is
probably characteristic of all the material of this type outcropping in that
locality.

8. That part of the potassium in the southern Illinois shale which is soluble
in sulfuric acid, is shown to be in a combination of the glaueonite type.

9. In southern Illinois shale having a potash content of 5.0 percent in the
raw condition or 5.6 percent when ignited, 62 percent of the total potash is
glauconitic in character and is available as plant food.

TABLE 3. ANALYSIS OF ILLINOIS SHALES*



Location


Sample
No.


Ash


Si0 3


A1 2 O 3


Fe 2 O 3


CaO


MgO


K 2


Na 2 O


Green shale above




















black shale at -


1


96.9












2.9




Caney creek . . .


2


97.7












3.5






3


86.2












5.2






4


88.0












5.7




Black shale at
Caney creek .... <


6

7
10


88.1
87.1
87.3


61.0
63.3
61.5


20.2
18.7
18.7


6.6
6.9
6.5


0.8
0.4
0.9


2.0
1.7
1.8


5.65
5.58
5.7


0.6
0.5
0.6




11


85.5


66.0


17.8


6.5


0.2


1.3


5.0


0.7




12


86.0












5.4




Black shale at State




















Pond


8


89.1












5.5




Black Shale at Moun-




















tain Glen


9


86 1












5 6




Green feldspathic




















shale at Dixon. . .


5


97.3












5.8





*The factors for SiO 2 , A1 2 O 3 , etc., are referred to the shale ash as 100 percent.



1921] PART II: GEOLOGY OF POTASH SHALE OF UNION COUNTY 237



PART II

GEOLOGY, DISTRIBUTION, AND OCCURRENCE OF THE
POTASH-BEARING SHALE OF UNION COUNTY

BY FRANK KEEY, STATE GEOLOGICAL SURVEY

The black potash-bearing shale of Union county comes to the sur-
face in a belt 75 to 200 feet wide along the west slope of the ridge that
lies about one mile west of Jonesboro, trends a little west of north, and
ends IVk miles south of Alto Pass, at Clear creek, in the Southwest 1/4
of Section 22, Township 11 South, Range 2 West. At its north end,
the shale is terminated by a northwest-southeast fault which brings
rock of the Chester age into contact with Devonian strata. The
southernmost exposure of the shale is seen in a narrow ravine in the
south-central part of Section 23, about half a mile north of the Ham-
burg road. South of the Hamburg road no black shale occurs, and
while both the overlying and underlying rocks may be seen in numer-
ous exposures, either the black shale was never deposited here or else
it was removed by erosion prior to the deposition of the overlying
green shale. The southern limit of the black shale is therefore within
half a mile north of the Hamburg road. The exact limit can readily be
determined by exploration.

TOPOGRAPHY

The ridge on whose western slope the black shale outcrops, is not
continuous but is interrupted at intervals by gaps formed where creeks
have cut their way thru the hills. Such gaps vary in width from
less than a quarter of a mile to more than half a mile. The crest of
the ridge is from 150 to 225 feet above the level of the creek flats,
and the horizon of the black shale is 40 to 100 feet below the crest of
the ridge except at the gaps where the easterly dip of the rock brings


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