Black and brown terrazzo chips from southern Illinois limestones

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ILLINOIS GEOLOGICAL
ILLINOIS STAT^GEOLOGICAL SURVEY SURVEY LIBRARY

prbana, Illinois AUG 2 1962

John C. Frye, Chief

V ILLINOIS
INDUSTRIAL MINERALS NOTES

Number] 15, July 25^ 1962

BLACK AND BROWN TERRAZZO CHIPS
FROM SOUTHERN ILLINOIS LIMESTONES

Richard D. Harvey

ABSTRACT

occurrlna I^nf ^ T °f dTSitS °f Very dark &*? to black l^estone
221 r i Unty and °f a reddish bro™ limestone in northern Alex-

lltrJT y " 8°UrCeS °f ChipS f°r USe in terrazzo was investigated. SznaU
terra^zo specimens were prepared and pertinent physical properties of the lime-

vere rJ!re d"ermlned in the Moratory. Favorable comments on these samples
Till llZr±£TJ:i:*ZZO Contract°«- *• Possibilities of developing these

limestones are discussed.

INTRODUCTION

water .nth Terrf?ZO ^ a W^dely used tvPe of flooring made by mixing cement and
water with small graded chips of marble, limestone, or dolomite. The mixture

iZJFll M° llaC& 3nd alWd to harden. The surface is then ground smooth
with abrasxve wheels and finally waxed and polished. In 1960, 434,000 tons of
cerrazzo chips were sold or used by producers in the United States, the value
of which was $5,140,000, or an average of $11.84 per ton (Cotter et al., 1961).

All terrazzo aggregates presently used in Illinois are imported from
ocner states and countries, as far as is known. Buff -colored chips are brought
irom Missouri and Tennessee, and aggregate of less common but highly desirable
colors such as black, green, brown, and white, generally comes from various
states along the Atlantic coast, Colorado, and Texas. Some stone is imported
trom Belgium, Italy, and parts of Africa.

tw • u Illinois has a variety of gray, light gray, and light buff limestones
tnac might make satisfactory terrazzo chips, but certain black or near -black
limestones in Hardin County and a reddish brown limestone in Alexander County
ooth in extreme southern Illinois, seemed unique within the state and were
given first attention. The black and brown limestones are, respectively parts
ot the Salem-St. Louis and St. Clair Formations.

- 2 -

LOCATION AND NATURE OF DEPOSITS

Black and Near-Black Limestones

The black and near-black limestone of the Salem-St. Louis Formation
in Hardin County appears to be best developed about 5 miles north of Rosiclare
in parts of sees. 4, 5, and 8, T. 12 S., R. 8 E., and sec. 26, T. 11 S., R. 7 E.,
where the stone is exposed along hill slopes, in stream beds, and low bluffs
along streams. The limestone is overlain by other limestone, cherty limestone,
residual chert, and clay and is underlain by a coarsely granular, light gray
limestone.

The black or near-black limestone is fine grained and fractures con-
choidally into somewhat elongated and sharp-edged fragments. It consists
principally of the mineral calcite with lesser amounts of fine-grained quartz,
clay, carbonaceous materials, and dolomite. At a few places, carbonaceous
partings occur between the limestone beds, and the stone in these beds is gen-
erally medium- to coarse-grained. Some of the limestone beds contain small
areas in which abundant minute grains of silica are dispersed. These, when
weathered, resemble nodules. They are, however, only slightly harder than the
surrounding rock and on polished or waxed surfaces are barely visible. Some
deposits contain tiny vertical veinlets of lighter colored calcite, and, in a
few beds, light colored fossil corals are present, some of which have incom-
plete rims of siliceous material.

The blackness of the stone is governed by its content of carbonaceous
matter and varies from one deposit to another. There also is a variation be-
tween the strata of a given deposit, some beds being quite black, others dark
gray or very dark gray. The greatest thickness of uniformly black stone seen
during this study was 6 feet in the S% of the SE% sec. 26, T. 11 S., R. 7 E.
Prospecting and further search may well reveal greater thicknesses. The exact
character and amount of the overburden on the black and near-black limestone
is not determinable because of forest vegetation on the slopes above the out-
crops. It probably consists of other limestone strata, some of them cherty,
that are gray and of brown or reddish clay. The thickness of the overburden
increases rapidly from a few feet at the outcrops of the black and near-black
limestone to about 35 feet away from the outcrops.

The following detailed descriptions illustrate some of the better

outcrops,

East-west gully in the NW% NW% NE% sec. 4, T. 12 S., R. 8 E.
Bed Description

21 Covered, soil; abundant chert fragments;
reddish clay

20 Limestone, fine to medium grained, near-
black

19 Covered

18 Limestone, black, fine grained, massive,
fractured

17 Covered

Thick

ness

(ft)

(in)

Up to

35

0

1

0

0

6

1

10

0

6

Thickness

(ft)

(in)

1

5

1

0

1

0

0

10

0

2

0

8

- 3 -
Bed Description

16 Limestone, black, fine grained, massive

15 Covered

14 Limestone, black, fine grained, massive

13 Limestone, black, fine grained, massive

12 Limestone, near-black, fine grained,

thin bedded
11 Limestone, black, fine grained, massive
10 Limestone, black, massive, with calcite

veinlets up to 1/8-inch thick; scattered

patchy concentrations of finely divided

silica 1 4

9 Limestone, near-black, massive 0 7

8 Limestone, near-black, thin bedded 0 1

7 Limestone, black, massive 0 9

6 Limestone, black, fine grained, massive;

scattered silica patches 2 6

5 Limestone, near-black, thin bedded 0 3

4 Limestone, near-black to black; some thin

carbonaceous lenses 1/4-inch thick 1 8

3 Limestone, near-black; interbedded

massive and thin beds 0 11

2 Covered 1 6

1 Limestone, near-black, medium grained, with

scattered light gray calcite veinlets 1 6

Stream bed

Beds 6 to 18, except for the covered intervals, were sampled for
this study and are possible source beds for terrazzo chips.

Small north-south gully in the center S% NW% NE£ sec. 8, T. 12 S.s

R. 8 E.

Bed Description

25 Covered, soil; abundant chert fragments;

reddish clay
24 Limestone, black, fine grained, massive;

some scattered fossil fragments, light

gray to near-black in color
23 Limestone, near-black, thin bedded
22 Limestone, black, fine grained, massive
21 Covered
20 Limestone, near-black, thin bedded, with

some silica patches
19 Covered
18 Limestone, black, fine grained, massive

17 Covered

16 Limestone, near-black to black, fine

grained, massive

Thickness

(ft)

(in)

Up to

20

0

9

0

9

0

9

0

6

1

0

0

6

0

4

1

0

- 4 -

Bed Description

15 Limestone, near-black to black, mostly

fine grained, thin bedded, especially on
weathered surfaces; patchy concentrations
of finely divided silica are present and
possible minor carbonaceous partings
14 Same as 15
13 Covered
12 Limestone, near-black, massive, mostly fine

grained; some light gray fossils (1/8-inch in
diameter) along some beds roughly 1 inch thick.
Some vertical veinlets of light gray calcite
11 Covered

10 Limestone, near-black, fine grained, massive;
some light gray fossil fragments
9 Covered
8 Limestone, near -black, medium to fine

grained, fossil if erous
7 Limestone, black, fine grained, massive
6 Covered

5 Limestone, black, fine grained
4 Covered
3 Limestone, near-black, medium to fine

grained, massive
2 Limestone, near-black, medium grained
1 Covered

Thickness
(ft) (in)

0
0
6

0
2

1
1

1
1
2
1
0

0
0

10
10

11

0

3
6

7
8
0
2
10

9
9

Beds 3 to 24, except for the covered intervals, were sampled for
this study and are possible sources for terrazzo chips.

In stream bed, center of N% SE% SE% sec. 26, T. 11 S., R. 7 E.

Bed Description

4 Soil

3 Limestone, black, with abundant black chert

nodules
2 Clay, silty, light gray and brown,

highly fractured
1 Limestone, black, fine grained, massive

with a few light gray fossils
Covered

Thickness
(ft)

5-6

3-4

6

Bed 1 was sampled for this study and is a possible source of ter-
razzo chips.

In addition to the foregoing, other outcrops of dark gray to black
limestone were noted in the NW£ NE% SE% sec. 8, T. 12 S., R. 8 E.; cen.
sec. 4, T. 12 S., R. 8 E.; SE% SW% NE^ sec. 28, T. 11 S., R. 8 E.j and SWfc NE%
NE% sec. 29, T. 11 S., R. 1 E.

- 5 -

Reddish Brown Limestone

The best outcrops noted of the reddish brown limestone of the
St, Clair Formation occur in the southwest corner and in the center of the
west half of sec. 12, T. 14 S., R. 3 W., Alexander County, about 2 miles east
of McClure. The samples tested were taken from the outcrop in the southwest
corner of the section where the following strata are exposed:

Bed Description Thickness

(ft)
3 Covered, soil; interbedded limestone,

silt, and shale (?) 10-30

2 Limestone, reddish brown with minor

mottlings of greenish brown 22

1 Limestone, very cherty, gray 15

Covered

The number 2 bed was sampled for this investigation. It is very
largely reddish brown, but about 10 percent of the rock is mottled greenish
brown. The mottling is roughly uniform throughout the 22 feet of rock, but
the limestone appears slightly less reddish brown in the upper 5 to 7 feet
than in the lower part. There are a few lens -shaped beds that appear to be
6 lightly clayey but most of the deposit probably is low in impurities. The
stone occurs in massive beds up to 7 feet thick.

The limestone is very fine grained and contains many small fossils
or fossil fragments up to about 1% mm long which can be observed only with a
microscope. It fractures into rough-surfaced, sharp-angled, somewhat elongated
chips. The mineralogical composition of a specimen examined in detail was more
than 97 percent calcite and less than 1 percent each of dolomite, quartz, and
clay minerals*

PHYSICAL TESTS AND RESULTS

The field samples, consisting of fist-sized or larger chunks, were
passed through a laboratory jaw crusher set at three-fourths of an inch. Any
material coarser than half an inch was re-run through the crusher re-set to
half an inch. The crushed material was screened into 4 sizes using square
opening screens, with the results shown below. The size fractions commonly
used for terrazzo aggregate are indicated by asterisks.

Size Percent by weight

Black limestone Reddish brown limes tons

Retained on 1/2-inch sieve 20.6 13.9

*Passing 1/2-inch, retained on 3/8-inch sieve 32.8 33.8

*Pa8sing 3/8-lnch, retained on 1/4-inch sieve 14.2 15.5

*Passing 1/4-inch, retained on 1/8-inch sieve 16.2 17.0

Passing 1/8-inch sieve 16.2 19.8

The above data do not necessarily indicate the percentages of dif-
ferent size-grade chips that would result from commercial crushing and screen-
ing, but they do give a rough idea of the breaking characteristics of the two
samples.

- 6 -

The Los Angeles wear test was made on the 3/8- to 1/2- and 1/2- to
3/4-inch size fractions of the two limestones in accordance with A6S.T.M.
Designation C 131-55, using grading B. The black and near-black limestone had
21 percent wear and the brown stone had 23 percent. Since a common require-
ment for stone used in concrete roads is that it have a Los Angeles wear of
not more than 35 percent, the two limestones may be regarded as having satis-
factory hardness.

Water absorption tests were made on the limestones by immersing three
or more pieces (roughly 3x3x1 inches) of each limestone in water for 72
hours and determining the increase in weight. The very dark gray and black
stone absorbed 0.06 percent water by weight and the brown stone 0.02 percent,
indicating a very low water absorption.

Test plaques of terrazzo were prepared from the black, near-black,
and reddish brown chips mixed with white portland cement, following in so far
as possible the usual commercial procedures. The plaques were smoothed on
grinding laps and coated with a wax sealer. They showed a uniformly even sur-
face, indicating that the aggregates and the cement were of about equal hard-
ness. It is believed these tests indicate that the chips possess desirable
characteristics as terrazzo aggregates.

CONCLUSIONS REGARDING TESTS

Various tests have been proposed for terrazzo aggregates (Kessler
et al., 1943), but as no limiting values have been set up defining the quality
of good aggregate the results of such tests are not definitely significant.
Therefore, our terrazzo test plaques were shown to several terrazzo contractors
who expressed favorable opinions regarding the color, hardness, and general
appearance of the terrazzo. These qualities and the low water absorption of
the black, near-black, and reddish brown limestone make them good possi-
bilities for terrazzo aggregate.

DEVELOPMENT CONSIDERATIONS

A major problem in connection with chips of the black, near-black,
and reddish brown limestones may be the maintenance of a uniform color or a
uniform range in colore The selection of deposits with a minimum color vari-
ation will obviously be desirable and selective quarrying of preferred beds may
be necessary. To assess the color of the stone as it will appear in terrazzo
it should be wet.

Selective quarrying may involve the removal of some stone unusable for
terrazzo chips, and the crushing of suitable stone will produce some chips
either too coarse or too fine to be used in terrazzo. A possible use for the
minus 1/8-inch fraction is agricultural limestone. A test run on this fraction
to determine neutralizing value of such stone gave a calcium carbonate equiv-
alent value of 80 percent for the black stone and 96 percent for the reddish
brown. The value for the black limestone is comparatively low but is within
the usable range. Other size fractions of this stone would be usable for road
surfacing and possibly for chips for bituminous roads. The fines and other
grades of the reddish brown limestone doubtless would have commercial use. Its
calcium carbonate equivalent is high and samples of the deposit have passed
tests for concrete aggregate and chips for bituminous roads (Lamar, 1959,
p. 31, 80).

- 7 -

The black and reddish brown limestone may also have possibilities
for use as stucco chips. The brown limestone probably will resist the weather
satisfactorily and hold its color. The weather resistance of the black and
near-black limestone has not been determined. Some of the dark colored lime-
stones develop a gray surface coating when weathered. The rate at which this
coating develops is not known but, though it is probably slow, the black chips
should be used with caution where they are exposed to the weather until their
durability is determined.

Terrazzo chips should be essentially free of rock dust, clay, and
shale. The deposits described contain insignificant amounts of clay and no
shale, but washing or other suitable processing may be required to reduce the
rock dusto

As indicated by the average price of $11.84 per ton for terrazzo ag-
gregate in 1960, these aggregates are premium materials. Indications from po-
tential users of the black and reddish brown chips are that a price of around
$20 per ton might be expected for the black and near-black chips and $15 for
the brown chips, f.o.b. the quarry. The possibility of such prices for the
chips may make their production economical even. thou3h quarrying and preparation
may involve considerably more expense than the quarrying of concrete aggregate,
road stone, and agstone.

Although the deposits of black stone are several miles from rail
transportation, there are good gravel roads throughout the region. The brown
stone is within 2 miles of a railroad.

USE OF BLACK OR BROWN LIMESTONE AS MARBLE

In addition to the possible use of the black and brown limestones for
terrazzo chips, they may be a potential source of commercial marble. The brown
limestone takes a good polish and has a pleasing mottled appearance. The thick
beds in which it occurs favor its processing by usual stone cutting methods.
The stone also may be usable for exterior construction, particularly in ac-
centing lighter colored stone.

Minor variations in composition among the various layers of the black
stone result in slight variations in its ability to accept a polish, but some
layers take a good polish (Lamar and Wiliman, 1955, p. 20). Commonly, thicker
beds are used for marble sawing than are present in these deposits, but as
black marble is uncommon the possibility that selected beds of the stone may
be sources of such marble is worthy of note.

REFERENCES

Cotter, P. G., and Jensen, N. C, 1961, Stone: Preprint from Minerals Yearbook,

1960: U. S. Bur. Mines, p. 12.
Kessler, D. W., Hockman, A., and Anderson, R. E., 1943, Physical properties of

terrazzo aggregates: U. S. Natl. Bur. Standards BMS 98, 19 p.
Lamar, J. E., 1959, Limestone resources of extreme southern Illinois: Illinois

Geol. Survey Rept. Inv. 211, 81 p.
Lamar, J. E., and Wiliman, H. B., 1955, Illinois building stones: Illinois

Geol. Survey Rept. Inv. 184, 24 p.