Some Curves from a 

Portable Differential 

Thermal Analysis 

Unit

GEOLOGICAL SURVEY BULLETIN 1021-G

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PORTABLE DIFFERENTIAL THERMAL ANALYSIS UNIT

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A CONTRIBUTION TO GENERAL GEOLOGY

SOME CURVES FROM A PORTABLE DIFFERENTIAL 

THERMAL ANALYSIS UNIT

By CAEOL J. PARKER, JOHN C. HATHAWAY, and PAUL D. BLACKMON

ABSTRACT

Differential thermal analysis curves obtained with a portable unit are given for 

some standard clay minerals and other materials commonly associated with clays.

INTRODUCTION

Hendricks, Goldich, and Nelson (1946) described a portable device 

for obtaining differential thermal curves. Portable differential 

thermal analysis units have since been used in studies of lateritic 

soils (Goldich and Bergquist, 1947, p. 55; 1948, p. 65) and have been 

applied to the identification of clay minerals and other aluminous 

materials by various workers in the U. S. Geological Survey. Inasmuch as the curves obtained with these instruments are not always 

comparable with those obtained using standard differential thermal 

analysis apparatus, the authors feel that a publication showing some 

standard mineral curves obtained with a portable unit may increase 

the usefulness of these instruments to the field geologist. The curves 

presented in this paper were therefore prepared to serve as a reference 

for the interpretation of results obtained from portable differential 

thermal analysis units. Clay minerals have been emphasized, but 

some of the minerals most commonly associated with them have been 

included.

PROCEDURE

The curves were obtained on the portable differential thermal 

analysis. apparatus shown in plate 28 by following the procedure 

described by Hendricks, Goldich, and Nelson (1946), supplemented 

by the instruction sheet accompanying the unit. The only departure 

from this procedure was in the preparation of the alundum (A12 03 ) 

to be used as the reference material. This was powdered and passed 

through a 400-mesh sieve in an effort to minimize differences in packing 

between the reference material and the sample.

The principal difference between the method used with the portable 

unit and the usual laboratory methods of differential thermal analysis

358701 56 237
238 CONTRIBUTIONS TO GENERAL GEOLOGY

lies in the rapid and nonuniform heating rate obtained with the 

portable unit. The type of heating rate used is shown by curve A of 

figure 43, in which the run is initiated with the furnace at full temperature. The principal advantage of starting the run with the 

furnace at full temperature is the short tune required for each run.

It is possible to achieve a less abrupt heating rate by the use of a 

rheostat in series with the furnace. Such a heating rate is shown by 

curve B of figure 43. This curve was obtained by starting the run 

with the furnace at room temperature and decreasing the resistance 

in steps, as shown on the graph. However, as the curves are recorded 

manually the longer heating period makes inefficient use of the 

operator's time. Besides, the furnace must be cooled before the 

next run can be made.

The disadvantages of the method in which the run is started with 

the furnace at full temperature are that it often causes severe broadening of the low temperature peaks and produces peaks that are not 

comparable in relative intensity with peaks produced by standard 

methods of differential thermal analysis. In addition, the temperatures at which the reactions occur do not always correspond exactly 

to the temperatures obtained for those reactions by apparatus in 

which the heating rate is uniform. A further effect is the small 

exothermic peak occurring at the beginning of most of the curves 

(figs. 44-51). Presumably this is the result of differences in specific 

heat, heat conductivity, and thermal diffusivity between the sample 

and the reference material. The temperature of the reference material 

apparently lags behind that of the sample when the sample block is 

subjected to the initial high thermal gradient imposed by the fully 

heated furnace.

The theory and methods of differential thermal analysis are 

described by Speil, Berkelhamer, Pask, and Davies (1945); Kerr and 

others (1949, Kept. 3); Smothers, Chiang, and Wilson (1951); and 

Grim (1953, p. 190-249).

COMPOSITION AND SOURCE OF SAMPLES

Table 1 lists the sample localities, and the major and minor constituents in each sample as determined by X-ray diffraction methods. 

Samples with numbers prefixed by H are clay mineral standards, 

described in American Petroleum Institute, Project 49, (Kerr and 

Others, 1949). Those with numbers prefixed by G are described by 

Grim, Machin, and Bradley (1945, p. 11). The samples with numbers 

prefixed by S are from the collection of the sedimentary petrology 

laboratory of the U. S. Geological Survey.
CURVES FROM DIFFERENTIAL THERMAL ANALYSIS UNIT 239

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240 .CONTRIBUTIONS TO GENERAL GEOLOGY 

TABLE 1. Constituents and localities of samples

Sample

H-l

4 

5 

9

12 

13

14 

19

23 

24 

25 

26 

28 

31

32 

33A

33B 

34

35

36 

41

42

49

G-866 

869

870 

871

Name

-____do_. -.---_

_.._.do_......_

 do_ ....

Halloysite.....

_____do__ -__-..

Dickite ___ ___

Montmorillonite. 

-_.._do_. ......

____-do--_-.-_

._.-_do_. -._-..

_.._.do_. ......

-.___do__------

.....do._.___._

-...-do........

Nontronite_ _ _ _ 

.. do. ..

Hectorite _ .._

Illite__ _ _' __

-____do__ ......

Ordovician

bentonite. 

__.-_do._ __ _

Pyrophyllite... 

Underclay. _

Kaolin.. ......

Shale... 

Plastic fireclay.

Constituents

Major

.....do...__._.

.....do.. .._.__

 do 

-----do___--__-

Montmorillonite. 

_____do_-_--_-_

 do 

-__-.do........

_.__. do.. .--_-_

.. ...do.. ------

 do 

--___do___--_-.

 do... -----

Hectorite _ _._

Hydrous mica_ _

 do_ 

Mixed-layered

hydrous mica. 

-____do___-____

Pyrophyllite... 

Hydrous mica..

Kaolinite.

Hydrous mica..

Minor

Montmorillonite.

Gibbsite, endellite? 

Gibbsite, endellite.

--.._do----.---.

Kaolinitic mineral, quartz. * 

Kaolinitic mineral.

Calcite ___ ..

Kaolinitic mineral, quartz.

Quartz__-_----_

Calcite, quartz __ 

Quartz, feldspar.

Quartz, mica,

kaolinite.

Kaolinitic mineral, quartz

Quartz. ________

Chlorite, quartz. 

Hydrous mica,

quartz.

Locality

Murfreesboro, 

Ark. 

Macon, Ga. 

Bath, S. C. 

Mesa Alta, N. 

Mex. 

Bedford, Ind.

Eureka, Utah.

Ouray, Colo. 

Polkville, Miss.

Chambers, Ariz. 

Otay, Calif. 

Upton, Wyo. 

Clay Spur, Wyo. 

Little Rock, Ark. 

Cameron, Ariz.

Pioche, Nev.

Garfield near 

Spokane, 

Wash. 

Manito near Spokane, Wash.

Hector, Calif.

Fithian, 111.

Morris, 111. 

Tazewell, Va.

High Bridge, Ky.

Bobbins, N. C.

Grundy County, in.

Union County, 

111.

Menard County,

111. 

Mexico, Mo.
CURVES FROM DIFFERENTIAL THERMAL ANALYSIS UNIT 241 

TABLE 1. Constituents and localities of samples Continued

Sample

G-875 

876

877 

878. 

880 

882

883 

S-l 

2 

3

4

5 

6

7

8

9 

10 

11

12

13

14 

15 

16

17

Name '

Bauxite ______

Hard kaolin 

Soft kaolin

Plastic kaolin. _

Ball clay__ ___

Fuller's earth __ 

Kaolin ________

Artificial gibbsite 

Bauxite. ._.-__

Attapulgite.-.- 

Sepiolite. ______

Boehmite _ ...

Brucite.. ______

Vermiculite____ 

. ....do.. --..__

Dioctahedral 

vermiculite

Phlogopite _ -.

Talc..-.--....

Quartz-._____.

Calcite__-_-__-

Dolomite......

Constituents

Major

Gibbsite... . .

Kaoiinite. _ _ _ _ _

_-_._do__--- .

_._._do_. ------

.._.. do.. _.....

Attapulgite.--- 

Kaoiinite .-_--.

Gibbsite____--_

.....do........

Attapulgite- .-- 

Sepiolite. _ _.

Boehmite___-__

Brucite.. ______

-____do___----_

Dioctahedral 

vermiculitic 

mineral

Phlogopite _ ..

Talc-.--------

Quartz.. ______

Calcite._-_---_

Minor

Kaolinite.---__

Montmorillonite, hydrous 

^mica

Montmorillonite.

Montmorillonite, quartz 

Quartz....----.

Kaolinite... ...

Montmorillonite, quartz 

Montmorillonite, calcite, 

quartz, dolomite 

Chlorite.-__--_-

.--_-do--__._-..

Antigorite, dolomite

Quartz, kaolinitic mineral, 

mica, hematite, feldspar

Locality

Irwinton, Ga. 

Gordon,. Ga.

t

Dry Branch, Ga. 

Do. 

Atwood, Tenn. 

Quincy, Fla.

Hobart Butte, 

Oreg. 

Bayer Process, 

ALCOA. 

Andersonville 

district, Ga. 

Attapulgus, Ga.

Algeria.

Linn, Mo. 

Drake, Mo. 

Bluemont, Md. 

(USNM 

102,836). 

Spruce Pine, N. 

C. 

North Carolina. 

South Africa. 

Middlesex County, N. J.

Locality unknown. 

Do. 

Do. 

Hot Springs, Ark. 

Grant County, 

N. Mex. 

Joplin, Mo. 

(USNM R2,409).

358701 5,6 2
CONTRIBUTIONS TO GENERAL GEOLOGY ... 

TABLE 1. Constituents and localities of samples Continued

Sample

S-18 

19

Name

Goethite...---

Constituents

Major

Goethite _-__--

Minor

Calcite.-- __--_

Locality

Sparta, N. J. 

(USNM 

80,070). 

Near Eufaula 

Ala. (USNM 

46,039).
CURVES FROM DIFFERENTIAL .THERMAL ANALYSIS UNIT 243

100 200 300 400 500 600 700 800 900 1000 

TEMPERATURE, IN DEGREES CENTIGRADE

FIOTJBE 44. Thermal analysis curves obtained with portable unit.
244 '' CONTRIBUTIONS TO GENERAL GEOLOGY

Low sensitivity 

Medium sensitivity

100 200 300 400 500 600 700 800 900 1000 

TEMPERATURE, IN DEGREES CENTIGRADE

FIGURE 45, Thermal analysis curves obtained with portable unit.
CURVES >FROM DIFFERENTIAL THERMAL ANALYSIS UNIT '245

A

A

\/

NONTRONITE

N

NONTRONITE 

X

MONTMORILLONITE H-34

H-33-A i

H-33-B

ILLITE H-35 / 

\

ORDOVICIAN BENTONITE

Low sensitivity 

Medium sensitivity

,H-36

100 200 300 ,400 500 600 700 800 900 1000 

TEMPERATURE, IN DEGREES CENTIGRADE

FIGURE 46. Thermal analysis curves obtained with portable unit.
246 -CONTRIBUTIONS TO--GENERAL GEOLOGY

A

ORDOVICIAN BENTONITE H-42

PYROPHYLLITE H-49

UNDERCLAY G-866

KAOLIN G-869

\ 

\

\

SHALE G-870

PLASTIC FIRECLAY G-871

0 100 200"" 300 400 500 600 700 800 900 1000

TEMPERATURE, IN DEGREES CENTIGRADE

- FIGURE 47.-Thermal analysis curves obtained with portable unit,
CURVES FR'OM DIFFERENTIAL-'THERMAL -ANALYSIS UNIT 247

HARD KAOLIN G-876 

\

SOFT KAOLIN G-877 

N

PLASTIC KAOLIN G-878

BALL CLAY G-880

V

\

FULLER'S EARTH G-882

KAOLIN G-883

v /

ARTIFICIAL GIBBSITE S-l

Low sensitivity 

Medium sensitivity

100 200 300 400 500 600 700 800 900 1000 

TEMPERATURE, IN DEGREES CENTIGRADE"

FIGTJEE 48. Thermal analysis curves obtained with portable unit.
-248 CONTRIBUTIONS TO GENERAL GEOLOGY

SEPIOLITE S-4

BOEHM TE S-5

DIASPORE S-6

BRUCITE S-7

ATTAPULGITE S-3

' Low sensitivity 

Medium sensitivity

O 100 200 300 400 500 600 700 800 900 1000

TEMPERATURE. IN DEGREES CENTIGRADE

FIOUEE 49. Thermal analysis curves obtained with portable Unit.
CURVES FROM DIFFERENTIAL THERMAL ANALYSIS UNIT 249-

100 200 300 400 500 600 700 800 

TEMPERATURE. IN DEGREES CENTIGRADE

900 1000

FIGURE 60. Thermal analysis curves obtained with portable unit.
250 CONTRIBUTIONS TO GENERAL GEOLOGY

CALCITE S-16

DOLOMITE S-17

SIDERITE S-18

GOETHITE S-19

Low sensitivity 

Medium sensitivity

f100 200 300 400 500 600 700 800 900 1000

TEMPERATURE, IN DEGREES CENTIGRADE

FIGURE 51. Thermal analysis curves obtained with portable unit.
CURVES FROM DIFFERENTIAL THERMAL ANALYSIS UNIT 251

REFERENCES CITED

Gokiich, S. S., and Bergquist, H. R., 1947, Aluminous lateritic soil of the Sierra

de Bahoruco area, Dominican Republic, West Indies: U. S. Geol. Survey

Bull. 953-C. 

 1948, Aluminous lateritic soil of the Republic of Haiti, W. I.: U. S. Geol.

Survey Bull. 954-C.

Grim, R. E., 1953, Clay mineralogy, New York, McGraw-Hill Book Co. 

Grim, R. E., Machin, J. S., and Bradley, W. F., 1945, Amenability of various

types of clay minerals to aluminum extraction by the lime sinter and lime

soda sinter processes: Illinois Geol. Survey Bull. 69. 

Hendricks, S. B., Goldich, S. S., and Nelson, R. A., 1946, A portable differential

thermal analysis unit for bauxite exploration: Econ. Geology, v. 41, p. 64-76. 

Kerr, P. F., and others, 1949-50, American Petroleum Institute, Project 49, Clay

Mineral Standards, Reports 1-8, New York, Columbia University Press. 

Smothers, W. J., Chiang, Y., and Wilson, A., 1951, Bibliography of differential

thermal analysis, University of Arkansas, Institute of Science and Technology, Research Series 21, 44 p. 

Speil, S., Berkelhamer, L. H., Pask, J. A., and Davies, B1., 1945, Differential

thermal analysis Its application to clays and other aluminous minerals:

U. S. Bur. of Mines Tech. Paper 664, 81 p.

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