If you do not need this report after it has served your purpose, please return it to 

the Geological Survey, using the official mailing label at the end

UNITED STATES DEPARTMENT OF THE INTERIOR 

Harold L. Ickes, Secretary

GEOLOGICAL SURVEY 

W. C. Mendenhall, Director

Bulletin S86-B

GEOLOGIC FACTOKS IN THE INTERPRETATION

OF FLUORSPAR RESERVES IN THE

ILLINOIS-KENTUCKY FIELD

BY

L. W. CURRIER

Prepared in cooperation with the 

ILLINOIS STATE GEOLOGICAL SURVET

Contributions to economic geology, 1937 

(Pages 5-14) ;

UNITED STATES

GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1937

For sa!e by the Superintendent of Documents, Washington, D. C. --- ..... Price 5 cents
ILLUSTRATIONS

CONTENTS

Abstract- ___-_----------------.-------_------..-__-----__-.------___ 5

Introduction. _____________________________________________________ 5

Value and nature of an estimate of reserves. _ -_-___----___-_-___-___ 6

Major geologic features of the field. _ _______________________________ 7

Vein deposits __ __-._-__-_.--_---_-._-____-___._-._____-__----___ 8

Bedding replacement deposits. - ________________ -_______^_____-______ 11

Life of the Illinois-Kentucky field- _ _ ___________________ ____________ 14

Page

PLATE 1. Production, importation, and utilization of fluorspar and production of open-hearth steel, 1916-35,.__. _-.-__-.________ 14

FIGURE 2. Map of Illinois-Kentucky fluorspar field_______.___.._._. 8

ii
GEOLOGIC FACTORS IN THE INTERPRETATION OF 

FLUORSPAR RESERVES IN THE ILLINOIS-KENTUCKY 

FIELD

By L. W. CUKRIER

ABSTRACT

The importance of fluorspar to the steel industry and the apparently small 

reserves in the Illinois-Kentucky field (which produces over 90 percent of the 

domestic fluorspar) make it desirable to evaluate the geologic factors upon 

which an earlier estimate of reserves has been made. The structural relations 

and origin of the deposits suggest an uneven distribution of deposits over the 

.area and greater depths of mineralization on some veins than on others. The 

Cave in Bock district of the Illinois portion of the field presents a unique geological relationship between the deposits, stratigraphic position, and minor 

structural features, and the potential resources of this district must be judged

 on a markedly different basis; a new estimate of reserves for this district 

places its future production at 500,000 tons or more. This figure should, however, be most useful as a stimulation for prospecting rather than as an even 

;moderately close estimate of resources, because assumptions must be made 

.regarding the percentage of the area that is mineralized; in other words, an 

uncertain areal factor is substituted for the uncertain depth factor of the 

veins.

The average yearly consumption of fluorspar in the United States for some 

.;years to come is estimated at 175,000 tons. This figure has been arrived at by

 considering statistics of production and utilization of both the fluorspar and 

steel industries. At this rate the estimated fluorspar reserves of the entire 

field will last from 30 to 35 years. This estimate will be affected by fluctuating 

imports, new utilization of fluorspar, and beneficiation of low-grade deposits, but 

no evaluation of these factors can be made. It is safe to say, however, that the 

Illinois-Kentucky field still has a considerable reserve of fluorspar and will

 continue to dominate domestic production for several years and that there is 

:no immediate cause for alarm concerning our resources of fluorspar.

INTRODUCTION

Fluorspar cannot be considered a deficiency mineral in the United 

'States at present. Domestic producers will probably be able to 

satisfy requirements for several decades, although proved reserves 

.are comparatively very small. The expectations are based upon 

rather comprehensive knowledge of the geologic factors governing

 the localization of the mineral in the Illinois-Kentucky field, from 

which over 90 percent of the domestic production is marketed. 

Nor should fluorspar be considered a strategic mineral in the gen-

 erally accepted sense of this term. Nevertheless, it is of great

138218 37 5
Q CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1937

importance in that it materially facilitates the production of openhearth steel, and consequently it definitely enters the war-minerals 

picture. For this reason a revised estimate of fluorspar reserves 

and an opinion regarding the life of the field in the light of recent 

geologic investigations are worth while/ VV;

For the most part the Illinois-Kentucky fluorspar field does not 

.lend itself even to a moderately close estimate of reserves. Except 

in a very few mines there .has been a lack of planned systematic 

and thorough explorations in advance of development. An area! 

view of the field appears to show that much of it has been superficially attacked for quick returns on. .small investments. This mode 

of procedure has necessarily been brought about by the limited use 

of the product arid the rapid and great fluctuations in the market. 

A glance at production and consumption curves (pi. 1) will suffice 

to demonstrate this fact.. It is axiomatic that the fluorspar-mining 

industry has been a shadow of the basic open-hearth steel industry 

anil has been subject therefore to the'vicissitudes of that industry, 

as from TO to 80 percent of the fluorspar produced goes to the steel 

plants. Fluctuating imports have clearly played an important part 

in the economic drama and have markedly, affected the demands; 

for domestic fluorspar, especially in periods of business depression 

the very times when domestic producers are in greatest need of an 

assured market. It is riot strange, therefore, that very few fluorspar 

mines have been in continuous production or development.

VALUE AND NATURE OF AN ESTIMATE OF RESERVES

Judgment of reserves is a'logical function of a public organization concerned with the geology of mineral resources. It provides 

an index of national independence as regards future supplies of 

the commodity considered and should be the key to policies of national conservation. It provides a basis for determining the relative positions of producing districts in the broad economic set-up 

of the industry. Knowledge of reserves, even though it may. be 

scant, aids in orienting the mining industry with respect to futureinvestment. It is 'a factor also in the solution of international aswell as national economic problems.

Unfortunately, by its very nature, a statement of probable reserves 

is not susceptible of being accurately expressed, for it is largely a. 

prophecy based upon intangible or incomplete evidence. The quantity of mineral available in a property, as Henry Louis has said, 

"is never known and never can be known until the whole of the 

"mineral has been worked out from the p'roperty in question, when 

the information is naturally worthless." Nevertheless, it is important to form some rational opinion of reserves, with full recognition,, 

of course, of the degree of uncertainty of the factors involved. In 

considering estimates of mineral reserves it must be fully realized
FLUORSPAR RESERVES IN ILLINOIS-KENTUCKY FIELD 7

that they represent only the nearest approach that can be made from 

the indefinite and variable data at hand. At best, the estimates can 

only approximate the mean between two probable and widely separated limits. If these facts are held clearly in mind,-it is justifiable 

to consider the matter of possible reserves even where mining development falls far short of indicating the extent and limits of mineralized ground in a district. Although a reasonably satisfactory 

calculation of possible reserves can be made only through development and exploration, nevertheless geologic interpretation of an 

area and its deposits may become of exceptional importance in the 

formulation of an opinion regarding the potentialities of a district. 

Through the study of developed mineral deposits, their structural, 

lithologic, and genetic features may often be determined and be used 

in the interpretation of the region as a whole, as well as in the search 

for specific areas worthy of exploration. As geologic conditions form 

so important a basis for the estimation of reserves, the pertinent 

geologic features of the Illinois-Kentucky fluorspar field and their 

bearing on the problem of reserves are reviewed below, and finally 

the expected life of the field is considered.

MAJOR GEOLOGIC FEATURES OF THE FIELD 1

The fluorspar deposits of the Illinois-Kentucky field are of two 

types vertical or nearly vertical veins in fault fissures and horizontal tabular and lenticular replacement bodies in limestone. The 

vein deposits constitute by far the bulk of the resources and are 

widely distributed throughout the field. The exploited horizontal 

replacement deposits are confined to a small area in Illinois on the 

margin of the field, known as the Cave in Eock district. (See fig. 2.)

The Illinois-Kentucky field displays a large structural dome of 

stratified rocks that has collapsed through faulting into a mosaic of 

elongated slabs and wedges. (See fig. 2.) The major surface dimensions of the dome are about 30 miles from northwest to southeast 

and 20 miles from northeast to southwest. The dome was invaded 

at depth by molten materials, some of which ascended along cracks 

and congealed as the peridotite dikes that are exposed at many 

places throughout the field. The chemical and mineralogic characteristics of these igneous bodies indicate that the constituents of the 

deep-seated magma from which they came had separated into materials of greatly contrasting chemical constitution before the intrusion and that one of the separate portions was exceptionally rich in 

volatile components. The known common association of the element 

fluorine with igneous rocks, the common occurrence of fluorspar in

1 Weller, Stuart, and collaborators, Geology of Hardin County: Illinois Geol. Survey 

Bull. 41, 1920. Currier, L. W., Fluorspar deposits of Kentucky: Kentucky Geol. Survey, 

ser. 6, vol. 13, 1923. Bastin, B. S., The fluorspar deposits of Hardin and Pope Counties, 

111.: Illinios Geol. Survey Bull. 58, 1931.
8

CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1937

veins of igneous affiliations, the structural and mineralogic features 

of the Illinois-Kentucky veins, and the coincidental geographic concentration of the fluorspar veins and the igneous rocks lead to the

10 Miles

FIGURE 2. Map of Illinois-Kentucky fluorspar field. Shaded area, Cave in Rock district, 

recently mapped in detail. PC, Peters Creek major fault zone. D, Devonian beds 

(oldest beds of the area). M, outcrop of base of Meramec group. Stippling, area of 

outcrop of lower formations of Chester group. U, outcrop of base of upper formations 

of Chester group. Condensed and abridged from a compiled map furnished through 

courtesy of J. Marvin Weller.

conclusion that the deposits were directly connected in origin with 

the molten material intruded beneath the domed area. The distribution of the veins and dikes throughout this area demark 

it from the surrounding territory as a mineral province in which 

fluorine-bearing solutions ascended along fault fissures from the 

deep-seated sources. The geographic center of the disturbed area is 

apparently in Kentucky, a short distance southeast of Rosiclare.

VEIN DEPOSITS

Fluorspar and calcite are the chief vein minerals, and they occur 

in different proportions in different parts of the same vein. In 

many places calcite is predominant, and at some points on produc-
FLUORSPAR RESERVES IN ILLINOIS-KENTUCKY FIELD Q

tive veins it is the only mineral present. At other places, on the 

other hand, it is entirely absent. Progressive or consistent changes 

in proportions of the two minerals with increasing depth have not 

been established for the field as a whole. It is true that at one 

mine in the Rosiclare district the vein appeared to change to a 

calcite vein at certain points below a depth of about 500 feet (AnnexExtension shafts), but there is sound reason to believe that this 

mine may be on a subordinate, divergent fissure. Elsewhere in the 

Rosiclare district the productive fluorspar vein has been followed 

below a depth of 700 feet. Until now most of the deep mining 

has been confined to the Illinois portion of the field, but it cannot 

logically be inferred, on the basis of known geologic facts, that the 

Kentucky veins are limited to shallower depths than those in Illinois. At one mine development has already exceeded a depth of 

400 feet. Also, on a theoretical basis, it is reasonable to expect 

that a generally decreasing concentration of fluorspar will be found 

toward the marginal belt of the field and that in this belt highgrade concentrations will be comparatively few and scattered.

The major fault fissures are commonly continuous for many miles, 

and some may extend beyond the mineralized area. Moreover, although the fault fissures may have considerable length, fluorspar 

masses may be markedly localized within them. Many of the fluorspar deposits have the form of lenticular bodies of commercial grade 

connected by lean or barren stretches. This is due to the mode of 

origin and character, of the faults. A fault surface rarely approaches 

a plane configuration, and the differential movement of the undulatory walls results in variable widths and spacings of the open portions of the fissure. As this feature is characteristic in vertical directions as well as horizontal, though perhaps to a lesser degree, the 

reaching of a "pinch" of the vein at depth does not in itself constitute an argument against sinking to greater depths.

Another structural feature of the veins that is not to be overlooked is that parallel fractures in any one system may converge 

and unite into a single fissure at depth. This condition is apparent 

at several places. It is clear, therefore, that a single depth factor, 

were it known, could not be applied to all the faults as exposed on 

the surface. It is altogether probable that there are certain very 

deep-seated fissures that were the controlling channels of access for 

solutions from the source of supply, and that solutions rising along 

these master channels were partly deflected into the diverging subordinate breaks, laterally as well as upward. Where the progress 

of solutions was lateral from the main fissure along a minor intersecting fissure, fluorspar concentration in the minor fissure might be 

expected to decrease gradually away from the intersection. This 

consideration, together with the convergence of fissures at depth and
10 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1937

possible progressive decrease in mineralization in the marginal areas 

of the field, clearly indicates that no matter what depth factor is 

assumed, or what ratio of concentration is calculated from existing 

development work on the veins, the total measured length of faults 

in the district is not a satisfactory measure of the extent of mineralized territory. It is worth while to recall at this point the wellknown fact that the amount of displacement in a fault is not a 

measure of the probability or degree of mineralization. In the first 

place, deeply extending fissures do not necessarily have a great displacement. Again, some faults, especially those of relatively great 

displacement, may have been so well sealed with gouge at some levels 

that solutions could not readily ascend along them at and above 

these levels, whereas some of their auxiliary fissures diverging at a 

lower horizon may have remained sufficiently open to receive concentrations of potential value.

There are doubtless many small veins that are undiscovered because of thick overburden, and many local rich deposits may be 

hidden within them. So far there is no known method of locating 

all or perhaps many of them. Geophysical methods may be very 

helpful in locating some of the faults, but geophysical data must be 

cautiously interpreted with respect to known geologic characteristics 

of the area. Recently resistivity methods have been successfully employed. Where positive results have been obtained, however, faults 

and not mineral bodies have been indicated, and the task of exploration remains before these faults can be considered potentially 

productive.

Other minerals commonly present in the fluorspar veins are galena, 

sphalerite, and quartz. Galena and sphalerite are valuable byproducts at some places and to the extent of their economic recovery 

play some part in the exploitation of a vein. Quartz is almost universally present, but in many veins it is present in inconsequential 

amounts. In some places, however, it is so abundant as to preclude 

treatment of the fluorspar by the usual milling practices, but considerable progress in milling methods has been made in recent years, 

and some highly siliceous fluorspar may be commercially workable in 

the future by the use of certain flotation methods.2 Although experimentation has been carried on primarily for the purpose of 

determining methods for producing fluorspar of acid grade (97 percent CaF2 and less than 2 percent Si02 ) from ordinary fluorspar 

and for the treatment of mill tailings, it has also been discovered that 

some highly siliceous fluorspar can be converted to a commercial

product, Beneficiation of this sort should have a marked effect

3 Coghill, W. H., and Greeman, O. W., Flotation of fluorspar ores for acid spar: U. S. 

Bur. Mines Kept. Inv. 2877, June 1928. Davis, H. W., Fluorspar in 1930: U. S. Bur. 

Mines Mineral Resources U. S., 1930, pt. 2, pp. 25-26, 1931.
FLUORSPAR RESERVES IN ILLINOIS-KENTUCKY FIELD H

upon fluorspar reserves as deposits of low-silica ores approach depletion.

The foregoing discussion points out the different geologic factors 

and uncertainties involved in attempts to estimate reserves of vein 

fluorspar in the Illinois-Kentucky field. In 1927 a joint committee 

of the American Institute of Mining and Metallurgical Engineers 

and the Mining and Metallurgical Society of America prepared an 

estimate of fluorspar reserves in this field. So far as the calculation 

applies to the vein deposits the estimate of approximately 5,000,000 

tons of milled fluorspar (at 70 percent recovery) seems reasonably 

conservative and cannot be definitely modified by quantitative data 

now at hand. Considering the geologic factors, however, the committee's estimate for the marginal belt of the field probably errs in 

being too high, whereas the estimate for the central area particularly for the Kentucky portion is probably too low. As suggested 

by the geologic facts stated above, the combined length of known 

faults, and limiting depths based on mine development to date seem 

to be unsatisfactory bases for calculation. On- the whole, however, 

it is the writer's opinion that the committee's total figure represents a 

rational and conservative estimate of the future expectancy in vein 

fluorspar as a national resource. Realization will, of course, be 

conditioned by the degree of thoughtfully planned and executed 

exploration and development, in which geologic interpretation and 

geophysical methods will play important parts.

BEDDING REPLACEMENT DEPOSITS

The fluorspar deposits in the Cave in Rock district are clearly replacement bodies in certain beds near the top of the thick Ste. Genevieve limestone. The limestone beds and hence the more or less 

tabular fluorspar bodies are essentially in a horizontal position, and 

the depth at which they occur can be rather closely determined from 

a knowledge of the areal geology. In the greater part of the developed area the chief ore zone is exposed along slopes and is easily 

opened through adits. Elsewhere exploration is satisfactorily accomplished by drilling. However, only a small amount of exploration 

has been done in advance of development, and the computation of 

reserves must be based largely on geologic data gained at the surface 

and interpreted through knowledge of the structural features, richness, and relationships of the known fluorspar bodies.

Certain stratigraphic and structural conditions appear to have 

controlled the deposition of fluorspar as bedding replacement bodies 

in this district. The most favorable horizon, so far as is indicated 

by development, is that part of the Ste. Genevieve limestone that 

directly underlies the Rosiclare sandstone member of the formation. 

The warped shale base of this sandstone forms the roof of fluorspar
12 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1937

bodies at this horizon. This shale is only a few inches to a few 

feet thick but appears to have formed an effective barrier to fluorinebearing solutions that rose along local or minor fissures. The fissures 

have little or no displacement. It is believed that they were favorable channels of access wherever they extended upward only to the 

impervious beds or were greatly reduced in passing from the limestone into the shale caprock. This termination or restriction may 

well have caused a "damming" effect upon solutions rising along 

the fissures and have forced them to penetrate laterally into the 

permeable and chemically susceptible limestone beds. As a result 

the beds were replaced more or less completely for considerable distances. It is conceived that these minor fissues were connected lower 

down with other channels and ultimately with a major fault zone. 

On this theory, extensive bedding replacement deposits are to be 

sought only in areas where a broad zone of minor fissuring and 

faulting lies adjacent to a major fault zone. It is unlikely that they 

would be commonly found in the walls of major fault zones, where 

ascension of solutions was relatively unhampered. The presence 

of a dense, impermeable bed, such as the shale base of the Rosiclare 

sandstone, or, subordinately, of dense limestone beds, is also a requirement. It is also reasonable to assume that such deposits will 

tend to be limited to marginal areas of the field.

A geologic estimate of reserves in the Cave in Kock district can 

be approached somewhat more satisfactorily than one of the vein 

deposits, not because the geologic features are more apparent, but 

because they can be evaluated better. As shown by the foregoing 

discussion, the geologic relations of the deposits permit elimination 

of the troublesome depth factor, and, if the theory of origin is correct, the probable areal distribution can be more satisfactorily 

prophesied on the basis of areal geology; moreover, the present 

mining developments furnish reasonable data for computing a concentration factor. Still, as is always true of the geologic approach 

to such a problem, certain assumptions must be made regarding 

the probable percentage of mineralized ground.

The factors involved in the calculation of reserves in the Cave 

in Kock district are (1) area of geologically favorable territory, 

(2) proportion of this area that is mineralized, (3) average thickness of mineral bodies, (4) percentage recovery of marketable 

fluorspar per unit of mined material.

Mapping and studies recently carried on in the district 3 indicate 

an area of about 1% square miles in which favorable geologic conditiQIls pay be present. Of this area about 150 acres is developed

and explored, 150 acres constitutes "probable" ground as indicated

1 Report in preparation on a cooperative project between the United States Geological 

Survey and the Illinois State Geological Survey, started in 1934 under auspices of the 

Public Works Administration, continued in 1935 by the two Surveys.
FLUORSPAR RESERVES IN ILLINOIS-KENTUCKY FIELD 1$

by prospects and drill records, and the remaining 600 to 700 acres 

constitutes "possible" ground in which the known major geologic 

features are favorable.

On the basis of data obtained in the mines of the district and of 

certain mining and milling data provided by the several companies,, 

the following factors have been derived for use in computing the 

reserves:

1. The average thickness of ore bodies in the mined territory is 

from 3 to 3y2 feet. This is actually an average measure of the chief 

mineralized zone in all the mines that were accessible at the time of 

the investigation.

2. The average fluorspar content of mined material is considered 

to be about 70 percent.

3. The average recovery of merchantable fluorspar from crude 

"ore" is believed to be about 75 percent.

4. About 30 percent of the "probable" and developed areas is. 

assumed to be mineralized.

5. The porosity of crude fluorspar as mined is liberally estimated 

at 10 percent.

By considering the weight of a cubic foot of pure fluorspar to be 

200 pounds, and applying all these factors to the 300 acres of developed and "probable" ground, the calculation gives. a probable 

supply of 556,000 tons. About 150,000 tons has already been 

marketed from the district. This leaves an estimate in "probable" 

ground of approximately 400,000 tons. If between 5 and 10 percent 

of the "possible" area is arbitrarily assumed to be mineralized, and 

the other concentration factors remain the same, it should contain a 

possible reserve of approximately 300,000 tons. The total calculated 

reserve would accordingly be about 700,000 tons. This estimate does 

not allow for fluorspar at lower horizons of the limestone which, 

according to recent explorations, may be appreciably productive. 

According to geologic inferences and the concentration data given, 

above, therefore, we may conservatively expect a total future production of 500,000 to 700,000 tons of marketable fluorspar (fluxing 

grade) from the district. In no sense, however, should any considerable part of this estimated total be looked upon as "blocked out." 

It should be clearly understood that the estimate rests largely upon, 

geologic interpretation and of necessity could not be based mostly 

on data obtained in mining exploration. It will probably be most 

useful in stimulating legitimate interest in certain undeveloped portions of the district and in supporting a reasonable opinion as. 

regards the potential resources of this materially important mineral.

It is interesting to note that the committee referred to above estimated the reserves of the Cave in Rock district to be only 80,000 tons. 

Since that estimate was made, notable developments have disclosed 

large fluorspar bodies and have extended the proved territory; also
14 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1937

since that time the district has marketed approximately 100,000 tons 

of fluorspar.

LIFE OF THE ILLINOIS-KENTUCKY FIELD

The present factors of utilization of fluorspar in the basic openhearth steel and other industries suggest that the average consumption of fluorspar in the United States for prosperous years comparable with 1928^29 will be between 150,000 and 200,000 tons. The 

import rate is now about 15,000 tons a year an amount that is 

negligible in the present calculation. At an assumed average yearly 

consumption of 175,000 tons, therefore, the estimated reserves of 

.5,500,000 or 6,000,000 tons will last 30 to 35 years.4

Several indeterminate economic factors will doubtless affect the 

production and reserves. In recent years there has been some increase in the use of fluorspar in industries other than steel making, 

Tmt so far this diversion has not had any marked effect, as is apparent 

from the curve in plate 1 showing the percentage of domestic fluorspar used in the steel industry. What the next few years will bring 

about in this direction depends, of course, not only upon general 

industrial progress but also upon chemical advances. It is highly 

improbable, however, that the steel industry will lose its domination 

of the fluorspar industry, and consequently the fluorspar operators

-will continue to find their chief markets in the steel-manufacturing

 districts.

There are many deposits of fluorspar of too low grade for present 

mining that should ultimately contribute to the resources through 

advances in milling methods. Lower-grade deposits Avill inevitably 

TDC of increasing importance with the gradual depletion of the highergrade deposits. Narrower veins will be worked and greater depths 

reached. Additional costs of mining and milling must necessarily 

"bring higher prices for the product. A considerable increase in the 

market price of fluxing fluorspar, however, should not be felt appreciably by the steel industry, because, according to the average utilization factor in 1935 of 6% pounds of fluorspar per ton of steel, the 

cost of the flux in 1935 was less than 4=y2 cents per ton of finished 

.steel.

Finally, although the present import level is low, there have been 

periods in recent years when domestic production has been greatly 

affected by large imports. (See pi. 1.) The future volume of imports and their consequent effect upon depletion of reserves cannot 

be prophesied.

4 StatiStiCS fOr PrOdUCtiOD, imports, and Utilization factors were obtained from data in 

31ineral Resources of the United States, published by the U. S. Geological Sui'Vfiy iPOffl 

1916 to 1923 and by the U. S. Bureau of Mines from 1924 to 1932 ; and in the Minerals 

Tearbook, published by the U. S. Bureau of Mines in 1933, 1934, and 1935 ; also from 

records of the U. S. Bureau of Mines, through the courtesy of the Director of that Bureau.

o
V. 9. GEOLOGICAL SURVEY BULLETIN 880 PLATE 1

FLUORSPAR 

THOUSANDS or

SHORT TONS

STEEL

MILLIONS or

GROSS TONS

ISIS 191? 19/3 1919 <9SO 1321 1922 /923 1924 1925 1926 1927 I92tl 1929 /93O 1931 1932 1933 I93+ 1935

TOJ>; ;EEL IND

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^-~ ,^

^

- 

hPOUNDS 

IO

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(I,. 50

POUNDS

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/^O /5i>/ I9tt 1933 1924 1925 /926 1927 /92G /32S> I93O 1931 I93S /

PRODUCTION, IMPORTATION, AND UTILIZATION OF FLUORSPAR AND PRODUCTION OF OPEN-HEARTH STEEL, 1916-35.