Transcriber’s Notes
Obvious typographical errors have been silently corrected. Variations
in hyphenation other spelling and punctuation remains unchanged. In
particular the words height and hight are used about equally. As hight
is a legitimate spelling, it has not been changed.
Some of the larger tables have been re-organised to improve clarity and
avoid excessive width.
The footnotes are located at the end of the book.
Italics are represented thus _italic_.
LEAD SMELTING
AND
REFINING
WITH SOME NOTES ON LEAD MINING
EDITED BY
WALTER RENTON INGALLS
[Illustration: Publisher’s Device]
NEW YORK AND LONDON
THE ENGINEERING AND MINING JOURNAL
1906
COPYRIGHT, 1906,
BY THE ENGINEERING AND MINING JOURNAL.
ALSO ENTERED AT
STATIONERS’ HALL, LONDON, ENGLAND.
ALL RIGHTS RESERVED.
PREFACE
This book is a reprint of various articles pertaining especially to the
smelting and refining of lead, together with a few articles relating
to the mining of lead ore, which have appeared in the _Engineering and
Mining Journal_, chiefly during the last three years; in a few cases
articles from earlier issues have been inserted, in view of their
special importance in rounding out certain of the subjects treated.
For the same reason, several articles from the _Transactions_ of
the American Institute of Mining Engineers have been incorporated,
permission to republish them in this way having been courteously
granted by the Secretary of the Institute. Certain of the other
articles comprised in this book are abstracts of papers originally
presented before engineering societies, or published in other technical
periodicals, subsequently republished in the _Engineering and Mining
Journal_, as to which proper acknowledgment has been made in all cases.
The articles comprised in this book relate to a variety of subjects,
which are of importance in the practical metallurgy of lead, and
especially in connection with the desulphurization of galena, which is
now accomplished by a new class of processes known as “Lime Roasting”
processes. The successful introduction of these processes into the
metallurgy of lead has been one of the most important features in
the history of the latter during the last twenty-five years. Their
development is so recent that they are not elsewhere treated in
technical literature, outside of the pages of the periodicals and the
transactions of engineering societies. The theory and practice of these
processes are not yet by any means well understood, and a year or two
hence we shall doubtless possess much more knowledge concerning them
than we have now. Prompt information respecting such new developments
is, however, more desirable than delay with a view to saying the
last word on the subject, which never can be said by any of us, even
if we should wait to the end of the lifetime. For this reason it
has appeared useful to collect and republish in convenient form the
articles of this character which have appeared during the last few
years.
W. R. INGALLS.
AUGUST 1, 1906.
CONTENTS
PART I
NOTES ON LEAD MINING
PAGE
SOURCES OF LEAD PRODUCTION IN THE UNITED STATES (WALTER
RENTON INGALLS) 3
NOTES ON THE SOURCE OF THE SOUTHEAST MISSOURI LEAD (H. A.
WHEELER) 10
MINING IN SOUTHEASTERN MISSOURI (WALTER RENTON INGALLS) 16
LEAD MINING IN SOUTHEASTERN MISSOURI (R. D. O. JOHNSON) 18
THE LEAD ORES OF SOUTHWESTERN MISSOURI (C. V. PETRAEUS AND
W. GEO. WARING) 24
PART II
ROAST-REACTION SMELTING
SCOTCH HEARTHS AND REVERBERATORY FURNACES
LEAD SMELTING IN THE SCOTCH HEARTH (KENNETH W. M. MIDDLETON) 31
THE FEDERAL SMELTING WORKS, NEAR ALTON, ILL. (O. PUFAHL) 38
LEAD SMELTING AT TARNOWITZ (EDITORIAL) 41
LEAD SMELTING IN REVERBERATORY FURNACES AT DESLOGE, MO.
(WALTER RENTON INGALLS) 42
PART III
SINTERING AND BRIQUETTING
THE DESULPHURIZATION OF SLIMES BY HEAP ROASTING AT BROKEN
HILL (E. J. HORWOOD) 51
THE PREPARATION OF FINE MATERIAL FOR SMELTING (T. J. GREENWAY) 59
THE BRIQUETTING OF MINERALS (ROBERT SCHORR) 63
A BRICKING PLANT FOR FLUE DUST AND FINE ORES (JAS. C. BENNETT) 66
PART IV
SMELTING IN THE BLAST FURNACE
MODERN SILVER-LEAD SMELTING (ARTHUR S. DWIGHT) 73
MECHANICAL FEEDING OF SILVER-LEAD BLAST FURNACES (ARTHUR S.
DWIGHT) 81
COST OF SMELTING AND REFINING (MALVERN W. ILES) 96
SMELTING ZINC RETORT RESIDUES (E. M. JOHNSON) 104
ZINC OXIDE IN SLAGS (W. MAYNARD HUTCHINGS) 108
PART V
LIME-ROASTING OF GALENA
THE HUNTINGTON-HEBERLEIN PROCESS 113
LIME-ROASTING OF GALENA (EDITORIAL) 114
THE NEW METHODS OF DESULPHURIZING GALENA (W. BORCHERS) 116
LIME-ROASTING OF GALENA (W. MAYNARD HUTCHINGS) 126
THEORETICAL ASPECTS OF LEAD-ORE ROASTING (C. GUILLEMAIN) 133
METALLURGICAL BEHAVIOR OF LEAD SULPHIDE AND CALCIUM SULPHATE
(F. O. DOELTZ) 139
THE HUNTINGTON-HEBERLEIN PROCESS (DONALD CLARK) 144
THE HUNTINGTON-HEBERLEIN PROCESS AT FRIEDRICHSHÜTTE (A.
BIERNBAUM) 148
THE HUNTINGTON-HEBERLEIN PROCESS FROM THE HYGIENIC STANDPOINT
(A. BIERNBAUM) 160
THE HUNTINGTON-HEBERLEIN PROCESS (THOMAS HUNTINGTON AND
FERDINAND HEBERLEIN) 167
MAKING SULPHURIC ACID AT BROKEN HILL (EDITORIAL) 174
THE CARMICHAEL-BRADFORD PROCESS (DONALD CLARK) 175
THE CARMICHAEL-BRADFORD PROCESS (WALTER RENTON INGALLS) 177
THE SAVELSBERG PROCESS (WALTER RENTON INGALLS) 186
LIME-ROASTING OF GALENA (WALTER RENTON INGALLS) 193
PART VI
OTHER METHODS OF SMELTING
THE BORMETTES METHOD OF LEAD AND COPPER SMELTING (ALFREDO
LOTTI) 215
THE GERMOT PROCESS (WALTER RENTON INGALLS) 224
PART VII
DUST AND FUME RECOVERY
FLUES, CHAMBERS AND BAG-HOUSES
DUST CHAMBER DESIGN (MAX J. WELCH) 229
CONCRETE IN METALLURGICAL CONSTRUCTION (HENRY W. EDWARDS) 234
CONCRETE FLUES (EDWIN H. MESSITER) 240
CONCRETE FLUES (FRANCIS T. HAVARD) 242
BAG-HOUSES FOR SAVING FUME (WALTER RENTON INGALLS) 244
PART VIII
BLOWERS AND BLOWING ENGINES
ROTARY BLOWERS VS. BLOWING ENGINES FOR LEAD SMELTING (EDITORIAL) 251
ROTARY BLOWERS VS. BLOWING ENGINES (J. PARKE CHANNING) 254
BLOWERS AND BLOWING ENGINES FOR LEAD AND COPPER SMELTING
(HIRAM W. HIXON) 256
BLOWING ENGINES AND ROTARY BLOWERS (S. E. BRETHERTON) 258
PART IX
LEAD REFINING
THE REFINING OF LEAD BULLION (F. L. PIDDINGTON) 263
THE ELECTROLYTIC REFINING OF BASE LEAD BULLION (TITUS ULKE) 270
ELECTROLYTIC LEAD REFINING (ANSON G. BETTS) 274
PART X
SMELTING WORKS AND REFINERIES
THE NEW SMELTER AT EL PASO, TEXAS (EDITORIAL) 285
NEW PLANT OF THE AMERICAN SMELTING AND REFINING COMPANY AT
MURRAY, UTAH (WALTER RENTON INGALLS) 287
THE MURRAY SMELTER, UTAH (O. PUFAHL) 291
THE PUEBLO LEAD SMELTERS (O. PUFAHL) 294
THE PERTH AMBOY PLANT OF THE AMERICAN SMELTING AND REFINING
COMPANY (O. PUFAHL) 296
THE NATIONAL PLANT OF THE AMERICAN SMELTING AND REFINING
COMPANY (O. PUFAHL) 299
THE EAST HELENA PLANT OF THE AMERICAN SMELTING AND REFINING
COMPANY (O. PUFAHL) 302
THE GLOBE PLANT OF THE AMERICAN SMELTING AND REFINING COMPANY
(O. PUFAHL) 304
LEAD SMELTING IN SPAIN (HJALMAR ERIKSSON) 306
LEAD SMELTING AT MONTEPONI, SARDINIA (ERMINIO FERRARIS) 311
PART I
NOTES ON LEAD MINING
SOURCES OF LEAD PRODUCTION IN THE UNITED STATES
BY WALTER RENTON INGALLS
(November 28, 1903)
Statistics of lead production are of value in two directions: (1) in
showing the relative proportion of the kinds of lead produced; and (2)
in showing the sources from which produced. Lead is marketed in three
principal forms: (_a_) desilverized; (_b_) soft; (_c_) antimonial, or
hard. The terms to distinguish between classes “a” and “b” are inexact,
because, of course, desilverized lead is soft lead. Desilverized lead
itself is classified as “corroding,” which is the highest grade, and
ordinary “desilverized.” Soft lead, referring to the Missouri product,
may be either “ordinary” or “chemical hard.” The latter is such lead
as contains a small percentage of copper and antimony as impurities,
which, without making it really hard, increase its resistance against
the action of acids, and therefore render it especially suitable
for the production of sheet to be used in sulphuric-acid chamber
construction and like purposes. The production of chemical hard lead
is a fortuitous matter, depending on the presence of the valuable
impurities in the virgin ores. If present, these impurities go into
the lead, and cannot be completely removed by the simple process of
refining which is practised. Nobody knows just what proportions of
copper and antimony are required to impart the desired property, and
consequently no specifications are made. Some chemical engineers call
for a particular brand, but this is really only a whim, since the same
brand will not be uniformly the same; practically one brand is as good
as another. Corroding lead is the very pure metal, which is suitable
for white lead manufacture. It may be made either from desilverized or
from the ordinary Missouri product; or the latter, if especially pure,
may be classed as corroding without further refining. Antimonial lead
is really an alloy of lead with about 15 to 30 per cent. antimony,
which is produced as a by-product by the desilverizers of base
bullion. The antimony content is variable, it being possible for the
smelter to run the percentage up to 60. Formerly it was the general
custom to make antimonial lead with a content of 10 to 12 per cent. Sb;
later, with 18 to 20 per cent.; while now 25 to 30 per cent. Sb is best
suited to the market.
The relative values of the various grades of lead fluctuate
considerably, according to the market place, and the demand and supply.
The schedules of the American Smelting and Refining Company make a
regular differential of 10c. per 100 lb. between corroding lead and
desilverized lead in all markets. In the St. Louis market, desilverized
lead used to command a premium of 5c. to 10c. per 100 lb. over ordinary
Missouri; but now they sell on approximately equal terms. Chemical hard
lead sells sometimes at a higher price, sometimes at a lower price,
than ordinary Missouri lead, according to the demand and supply. There
is no regular differential. This is also the case with antimonial
lead.[1]
The total production of lead from ores mined in the United States in
1901 was 279,922 short tons, of which 211,368 tons were desilverized,
57,898 soft (meaning lead from Missouri and adjacent States) and
10,656 antimonial. These are the statistics of “The Mineral Industry.”
The United States Geological Survey reported substantially the same
quantities. In 1902 the production was 199,615 tons of desilverized,
70,424 tons of soft, and 10,485 tons of antimonial, a total of 280,524
tons. There is an annual production of 4000 to 5000 tons of white
lead direct from ore at Joplin, Mo., which increases the total lead
production of the United States by, say, 3500 tons per annum. The
production of lead reported as “soft” does not represent the full
output of Missouri and adjacent States, because a good deal of their
ore, itself non-argentiferous, except to the extent of about 1 oz. per
ton in certain districts, is smelted with silver-bearing ores, going
thus into an argentiferous lead; while in one case, at least, the
almost non-argentiferous lead, obtained by smelting the ore unmixed, is
desilverized for the sake of the extra refining.
Lead-bearing ores are of widespread occurrence in the United States.
Throughout the Rocky Mountains there are numerous districts in which
the ore carries more or less lead in connection with gold and silver.
For this reason, the lead mining industry is not commonly thought of as
having such a concentrated character as copper mining and zinc mining.
It is the fact, however, that upward of 70 per cent. of the lead
produced in the United States is derived from five districts, and in
the three leading districts from a comparatively small number of mines.
The statistics of these for 1901 to 1904 are as follows:[2]
┌──────────┬───────────────────────────────┬───────────────────────┬────
│ │ PRODUCTION, TONS │ PER CENT. │
│DISTRICT │ 1901 │ 1902 │ 1903 │ 1904 │ 1901│ 1902│ 1903│ 1904│REF.
├──────────┼───────┼───────┼───────┼───────┼─────┼─────┼─────┼─────┼────
│Cœur │ │ │ │ │ │ │ │ │
│d’Alene │ 68,953│ 74,739│ 89,880│ 98,240│ 24.3│ 26.3│ 32.5│ 32.5│_a_
│Southeast │ │ │ │ │ │ │ │ │
│Mo. │ 46,657│ 56,550│ 59,660│ 59,104│ 16.4│ 19.9│ 21.2│ 19.6│_b_
│Leadville,│ │ │ │ │ │ │ │ │
│Colo. │ 28,180│ 19,725│ 18,177│ 23,590│ 10.0│ 6.9│ 6.6│ 7.8│_c_
│Park City,│ │ │ │ │ │ │ │ │
│Utah │ 28,310│ 36,300│ 36,534│ 30,192│ 10.0│ 12.8│ 13.2│ 10.0│_d_
│Joplin, │ │ │ │ │ │ │ │ │
│Mo.-Kan. │ 24,500│ 22,130│ 20,000│ 23,600│ 8.6│ 7.8│ 7.2│ 7.8│_e_
│ ├───────┼───────┼───────┼───────┼─────┼─────┼─────┼─────┤
│ Total │196,600│209,444│224,251│234,726│ 69.3│ 73.7│ 81.0│ 77.7│
_a._ The production in 1901 and 1902 is computed from direct returns
from the mines, with an allowance of 6 per cent. for loss of lead in
smelting. The production in 1903 and 1904 is estimated at 95 per cent.
of the total lead product of Idaho.
_b._ This figure includes only the output of the mines at Bonne Terre,
Flat River, Doe Run, Mine la Motte and Fredericktown. It is computed
from the report of the State Lead and Zinc Mine Inspector as to ore
produced, the ore (concentrates) of the mines at Bonne Terre, Flat
River and Doe Run being reckoned as yielding 60 per cent. lead.
_c._ Report of State Commissioner of Mines.
_d._ Report of Director of the Mint on “Production of Gold and Silver
in the United States,” with allowance of 6 per cent. for loss of lead
in smelting.
_e._ From statistics reported by “The Mineral Industry,” reckoning the
ore (concentrates) as yielding 70 per cent. lead.
Outside of these five districts, the most of the lead produced in the
United States is derived from other camps in Idaho, Colorado, Missouri
and Utah, the combined output of all other States being insignificant.
It is interesting to examine the conditions under which lead is
produced in the five principal districts.
_Leadville, Colo._—The mines of Leadville, which once were the largest
lead producers of the United States, became comparatively unimportant
after the exhaustion of the deposits of carbonate ore, but have
attained a new importance since the successful introduction of means
for separating the mixed sulphide ore, which occurs there in very large
bodies. The lead production of Leadville in 1897 was 11,850 tons;
17,973 tons in 1898; 24,299 tons in 1899; 31,300 tons in 1900; 28,180
tons in 1901, and 19,725 tons in 1902. The Leadville mixed sulphide ore
assays about 8 per cent. Pb, 25 per cent. Zn and 10 oz. silver per ton.
It is separated into a zinc product assaying about 38 per cent. Zn and
6 per cent. Pb, and a galena product assaying about 45 per cent. Pb, 10
or 12 per cent. Zn, and 10 oz. silver per ton.
_Cœur d’Alene._—The mines of this district are opened on fissure veins
of great extent. The ore is of low grade and requires concentration. As
mined, it contains about 10 per cent. lead and a variable proportion
of silver. It is marketed as mineral, averaging about 50 per cent. Pb
and 30 oz. silver per ton. The production of lead ore in this district
is carried on under the disadvantages of remoteness from the principal
markets for pig lead, high-priced labor, and comparatively expensive
supplies. It enjoys the advantages of large orebodies of comparatively
high grade in lead, and an important silver content, and in many cases
cheap water power, and the ability to work the mines through adit
levels. The cost of mining and milling a ton of crude ore is $2.50 to
$3.50. The mills are situated, generally, at some distance from the
mines, the ore being transported by railway at a cost of 8 to 20c.
per ton. The dressing is done in large mills at a cost of 40 to 50c.
per ton. About 75 per cent. of the lead of the ore is recovered. The
concentrates are sold at 90 per cent. of their lead contents and 95 per
cent. of their silver contents, less a smelting charge of $8 per ton,
and a freight rate of $8 per ton on ore of less than $50 value per ton,
$10 on ore worth $50 to $65, and $12 on ore worth more than $65; the
ore values being computed f. o. b. mines. The settling price of lead is
the arbitrary one made by the American Smelting and Refining Company.
With lead (in ore) at 3.5c. and silver at 50c., the value, f. o. b.
mines, of a ton of ore containing 50 per cent. Pb and 30 oz. silver is
approximately as follows:
1000 × 0.90 = 900 lb. lead, at 3.5c. $31.50
30 × 0.95 = 28.5 oz. silver, at 50c. 14.25
——————
Gross value, f. o. b. mines $45.75
Less freight, $10, and smelting charge, $8 18.00
——————
Net value, f. o. b. mines $27.75
Assuming an average of 6 tons of crude ore to 1 ton of concentrate, the
value per ton of crude ore would be about $4.62½, and the net profit
per ton about $1.62½, which figures are increased 23.75c. for each 5c.
rise in the value of silver above 50c. per ounce.
The production of the Cœur d’Alene since 1895, as reported by the
mines, has been as follows:
─—─—─—-———─—─┬—─—-——————─—─┬—─—-—————————┬——————─—─
YEAR │ LEAD, TONS │ SILVER, OZ. │ RATIO[3]
─—─—─—-———─—─┼—─—-——————─—─┼—─—-—————————┼——————─—─
1896 │ 37,250 │ 2,500,000 │ 67.1
1897 │ 57,777 │ 3,579,424 │ 61.9
1898 │ 56,339 │ 3,399,524 │ 60.3
1899 │ 50,006 │ 2,736,872 │ 54.7
1900 │ 81,535 │ 4,755,877 │ 58.3
1901 │ 68,953 │ 3,349,533 │ 48.5
1902 │ 74,739 │ 4,489,549 │ 60.0
1903 │ [4]100,355 │ 5,751,613 │ 57.3
1904 │ [4]108,954 │ 6,247,795 │ 57.4
─—─—─—-———─—─┴—─—-——————─—─┴—─—-—————————┴——————─—─
The number of producers in the Cœur d’Alene district is comparatively
small, and many of them have recently consolidated, under the name of
the Federal Mining and Smelting Company. Outside of that concern are
the Bunker Hill & Sullivan, the Morning and the Hercules mines, control
of which has lately been secured by the American Smelting and Refining
Company.
_Southeastern Missouri._—The most of the lead produced in this region
comes from what is called the disseminated district, comprising
the mines of Bonne Terre, Flat River, Doe Run, Mine la Motte and
Fredericktown, of which those of Bonne Terre and Flat River are the
most important. The ore of this region is a magnesian limestone
impregnated with galena. The deposits lie nearly flat and are very
large. They yield about 5 per cent. of mineral, which assays about 65
per cent. lead. The low grade of the ore is the only disadvantage which
this district has, but this is so much more than offset by the numerous
advantages, that mining is conducted very profitably, and it is an open
question whether lead can be produced more cheaply here or in the Cœur
d’Alene. The mines of southeastern Missouri are only 60 to 100 miles
distant from St. Louis, and are in close proximity to the coalfields
of southern Illinois, which afford cheap fuel. The ore lies at depths
of only 100 to 500 ft. below the surface. The ground stands admirably,
without any timbering. Labor and supplies are comparatively cheap.
Mining and milling can be done for $1.05 to $1.25 per ton of crude ore,
when conducted on the large scale that is common in this district.
Most of the mining companies are equipped to smelt their own ore, the
smelters being either at the mines or near St. Louis. The freight rate
on concentrates to St. Louis is $1.40 per ton; on pig lead it is $2.10
per ton. The total cost of producing pig lead, delivered at St. Louis,
is about 2.25c. per pound, not allowing for interest on the investment,
amortization, etc.
The production of the mines in the disseminated district in 1901 was
equivalent to 46,657 tons of pig lead; in 1902 it was 56,550 tons. The
milling capacity of the district is about 6000 tons per day, which
corresponds to a capacity for the production of about 57,000 tons of
pig lead per annum. The St. Joseph Lead Company is building a new 1000
ton mill, and the St. Louis Smelting and Refining Company (National
Lead Company) is further increasing its output, which improvements will
increase the daily milling capacity by about 1400 tons, and will enable
the district to put out upward of 66,000 tons of pig lead. In this
district, as in the Cœur d’Alene, the industry is closely concentrated,
there being only nine producers, all told.
_Park City, Utah._—Nearly all the lead produced by this camp comes
from the Silver King, Daly West, Ontario, Quincy, Anchor and Daly
mines, which have large veins of low-grade ore carrying argentiferous
galena and blende, a galena product being obtained by dressing, and
zinkiferous tailings, which are accumulated for further treatment as
zinc ore, when market conditions justify.[5]
_Joplin District._—The lead production of southwestern Missouri and
southeastern Kansas, in what is known as the Joplin district, is
derived entirely as a by-product in dressing the zinc ore of that
district. It is obtained as a product assaying about 77 per cent. Pb,
and is the highest grade of lead ore produced, in large quantity,
anywhere in the United States. It is smelted partly for the production
of pig lead, and partly for the direct manufacture of white lead. The
lead ore production of the district was 31,294 tons in 1895, 26,927
tons in 1896, 29,578 tons in 1897, 26,457 tons in 1898, 24,100 tons
in 1899, 28,500 tons in 1900, 35,000 tons in 1901, and 31,615 tons in
1902. The production of lead ore in this district varies more or less,
according to the production of zinc ore, and is not likely to increase
materially over the figure attained in 1901.
NOTES ON THE SOURCE OF THE SOUTHEAST MISSOURI LEAD
BY H. A. WHEELER
(March 31, 1904)
The source of the lead that is being mined in large quantities in
southeastern Missouri has been a mooted question. Nor is the origin
of the lead a purely theoretical question, as it has an important
bearing on the possible extension of the orebodies into the underlying
sandstone.
The disseminated lead ores of Missouri occur in a shaly, magnesian
limestone of Cambrian age in St. François, Madison and Washington
counties, from 60 to 130 miles south of St. Louis. The limestone
is known as the Bonne Terre, or lower half of “the third magnesian
limestone” of the Missouri Geological Survey, and rests on a sandstone,
known as “the third sandstone,” that is the base of the sedimentary
formations in the area. Under this sandstone occur the crystalline
porphyries and granites of Algonkian and Archean age, which outcrop as
knobs and islands of limited extent amid the unaltered Cambrian and
Lower Silurian sediments.
The lead occurs as irregular granules of galena scattered through the
limestone in essentially horizontal bodies that vary from 5 to 100
ft. in thickness, from 25 to 500 ft. in width, and have exceeded 9000
ft. in length. There is no vein structure, no crushing or brecciation
of the inclosing rock, yet these orebodies have well defined axes or
courses, and remarkable reliability and persistency. It is true that
the limestone is usually darker, more porous, and more apt to have thin
seams of very dark (organic) shales where it is ore-bearing than in the
surrounding barren ground. The orebodies, however, fade out gradually,
with no sharp line between the pay-rock and the non-paying, and the
lead is rarely, if ever, entirely absent in any extent of the limestone
of the region. While the main course of the orebodies seems to be
intimately connected with the axes of the gentle anticlinal folds,
numerous cross-runs of ore that are associated with slight faults are
almost as important as the main shoots, and have been followed for
5000 ft. in length. These cross-runs are sometimes richer than the
main runs, at least near the intersections, but they are narrower, and
partake more of the type of vertical shoots, as distinguished from the
horizontal sheet-form.
Most of the orebodies occur at, or close to, the base of the limestone,
and frequently in the transition rock between the underlying sandstone
and the limestone, though some notable and important bodies have
been found from 100 to 200 ft. above the sandstone. This makes the
working depth from the surface vary from 150 to 250 ft., for the upper
orebodies, to 300 to 500 ft. deep to the main or basal orebodies,
according as erosion has removed the ore-bearing limestone. The
thickness of the latter ranges from 400 to 500 ft.
Associated with the galena are less amounts of pyrite, which especially
fringes the orebodies, and very small quantities of chalcopyrite, zinc
blende, and siegenite (the double sulphide of nickel and cobalt).
Calcite also occurs, especially where recent leaching has opened
vugs, caves, or channels in the limestone, when secondary enrichment
frequently incrusts these openings with crystals of calcite and galena.
No barite ever occurs with the disseminated ore, though it is the
principal gangue mineral in the upper or Potosi member of the third
magnesian limestone, and is never absent in the small ore occurrences
in the still higher second magnesian limestone.
While the average tenor of the ore is low, the yield being from 3 to
4 per cent. in pig lead, they are so persistent and easy to mine that
the district today is producing about 70,000 tons of pig lead annually,
and at a very satisfactory profit. As the output was about 2500 tons
lead in 1873, approximately 8500 tons in 1883, and about 20,000 tons in
1893, it shows that this district is young, for the principal growth
has been within the last five years.
Of the numerous but much smaller occurrences of lead elsewhere in
Missouri and the Mississippi valley, none resembles this district
in character, a fact which is unique. For while the Mechernich lead
deposits, in Germany, are disseminated, and of even lower grade than in
Missouri, they occur in a sandstone, and (like all the lead deposits
outside of the Mississippi valley) they are argentiferous, at least to
an extent sufficient to make the extraction of the silver profitable;
and on the non-argentiferous character of the disseminated deposits
hangs my story.
Of the numerous hypotheses advanced to account for the origin of these
deposits, there are only two that seem worthy of consideration: (a)
the _lateral secretion theory_, and (b) _deposition from solutions of
deep-seated origin_. Other theories evolved in the pioneer period of
economic geology are interesting, chiefly by reason of the difficulties
under which the early strugglers after geological knowledge blazed the
pathway for modern research and observation.
The lateral secretion theory, as now modernized into the secondary
enrichment hypothesis, has much merit when applied to the southeastern
and central Missouri lead deposits. For the limestones throughout
Missouri—and they are the outcropping formation over more than half of
the State—are rarely, if ever, devoid of at least slight amounts of
lead and zinc, although they range in age from the Carboniferous down
to the Cambrian.
The sub-Carboniferous formation is almost entirely made up of
limestones, which aggregate 1200 to 1500 ft. in thickness. They
frequently contain enough lead (and less often zinc) to arouse the
hopes of the farmer, and more or less prospecting has been carried on
from Hannibal to St. Louis, or 125 miles along the Mississippi front,
and west to the central part of the State, but with most discouraging
results.
In the rock quarries of St. Louis, immediately under the lower coal
measures, fine specimens of millerite of world-wide reputation occur
as filiform linings of vugs in this sub-Carboniferous limestone. These
vugs occur in a solid, unaltered rock which gives no clue to the
existence of the vug or cavity until it is accidentally broken. The
vugs are lined with crystals of pink dolomite, calcite and millerite,
with occasionally barite, selenite, galena and blende. They occur
in a well-defined horizon about 5 ft. thick, and the vugs in the
limestone above and below this millerite bed contain only calcite,
or less frequently dolomite. Yet this sub-Carboniferous formation in
southwestern Missouri, about Joplin, carries the innumerable pockets
and sheets of lead and zinc that have made that district the most
important zinc producer in the world. While faulting and limited
folding occur in eastern and central Missouri to fully as great an
extent as in St. François county or the Joplin district, thus far no
mineral concentration into workable orebodies has been found in this
formation, except in the Joplin area.
The next important series of limestones that make up most of the
central portion of Missouri are of Silurian age, and in them lead and
zinc are liberally scattered over large areas. In the residual surface
clays left by dissolution of the limestone, the farmers frequently make
low wages by gophering after the liberated lead, and the aggregate
of these numerous though insignificant gopher-holes makes quite a
respectable total. But they are only worked when there is nothing else
to do on the farm, as with rare exceptions they do not yield living
wages, and the financial results of mining the rock are even less
satisfactory. Yet a few small orebodies have been found that were
undoubtedly formed by local leaching and re-precipitation of this
diffused lead and zinc. Such orebodies occur in openings or caves,
with well crystallized forms of galena and blende, and invariably
associated with crystallized “tiff” or barite. I am not aware of any
of these pockets or secondary enrichments having produced as much as
2000 tons of lead or zinc, and very few have produced as much as 500
tons, although one of these pockets was recently exploited with heroic
quantities of printer’s ink as the largest lead mine in the world. Yet
there are large areas in which it is almost impossible to put down a
drill-hole without finding “shines” or trifling amounts of lead or
zinc. That these central Missouri lead deposits are due to lateral
secretion there seems little doubt, and it is possible that larger
pockets may yet be found where more favorable conditions occur.
When the lateral secretion theory is applied to the disseminated
deposits of southeastern Missouri, we are confronted by enormous bodies
of ore, absence of barite, non-crystallized condition of the galena
except in local, small, evidently secondary deposits, and well-defined
courses for the main and cross-runs of ore. The Bonne Terre orebody,
which has been worked longest and most energetically, has attained a
length of nearly 9000 ft., with a production of about 350,000 tons
or $30,000,000 of lead, and is far from being exhausted. Orebodies
recently opened are quite as promising. The country rock is not as
broken nor as open as in central Missouri, and is therefore much less
favorable for the lateral circulation of mineral waters, yet the
orebodies vastly exceed those of the central region.
Further, the Bonne Terre formation is heavily intercalated with thick
sheets of shale that would hinder overlying waters from reaching the
base of the ore-horizon, where most of the ore occurs, so that the
leachable area would be confined to a very limited vertical range,
or to but little greater thickness than the 100 ft. or so in which
most of the orebodies occur. While I have always felt that such large
bodies, showing relatively rapid precipitation of the lead, could not
be satisfactorily explained except as having a deep-seated origin,
the fact that the disseminated ore is practically non-argentiferous,
or at least carries only one to three ounces per ton, has been a
formidable obstacle. For the lead in the small fissure-veins that
occasionally occur in the adjacent granite has always been reported
as argentiferous. Thus the Einstein silver mine, near Fredericktown,
worked a fissure-vein from 1 to 6 ft. wide in the granite. It had a
typical complex vein-filling and structure, and carried galena that
assayed from 40 to 200 oz. per ton. While the quantity of ore obtained
did not justify the expensive plant erected to operate it, the galena
was rich in silver, whereas in the disseminated ores at the Mine la
Motte mine, ten miles distant, only the customary 1.5 oz. per ton
occurs. Occasionally fine-grained specimens of galena that I have found
in the disseminated belt would unquestionably be rated as argentiferous
by a Western miner, but the assay showed that the structure in this
case was due to other causes, as only about two ounces were found.
An apparent exception was reported at the Peach Orchard diggings,
in Washington county, in the higher or Potosi member of the third
magnesian limestone, where Arthur Thacher found sulphide and carbonate
ore carrying 8 to 10 oz. of silver per ton; and a short-lived hamlet,
known as Silver City, sprang up to work them. I found, however, that
these deposits are associated with little vertical fissure-veins or
seams that unquestionably come up from the underlying porphyry.
Recently I examined the Jackson Revel mine, which has been considered
a silver mine for the last fifty years. It lies about seven miles
south of Fredericktown, and is a fissure-vein in Algonkian felsite,
where it protrudes, as a low hill, through the disseminated limestone
formation. A shaft has just been sunk about 150 ft. at less than
1000 ft. from the feather edge of the limestone. The vein is narrow,
only one to twelve inches wide, with slicken-sided walls, runs about
N. 20 deg. E., and dips 80 to 86 deg. eastward. White quartz forms
the principal part of the filling; the vein contains more or less
galena and zinc blende. Assays of the clean galena made by Prof. W. B.
Potter show only 2.5 oz. silver per ton, or no more than is frequently
found in the disseminated lead ores. As the lead in this fissure vein
may be regarded as of undoubted deep origin, and it is practically
non-argentiferous, this would seem to remove the last objection to
the theory of the deep-seated source of the lead in the disseminated
deposits of southeast Missouri.
MINING IN SOUTHEASTERN MISSOURI
BY WALTER RENTON INGALLS
(February 18, 1904)
The St. Joseph Lead Company, in the operation of its mines at Bonne
Terre, does not permit the cages employed for hoisting purposes to be
used for access to the mine. Men going to and from their work must
climb the ladders. This rule does not obtain in the other mines of the
district. The St. Joseph Lead Company employs electric haulage for
the transport of ore underground at Bonne Terre. In the other mines
of the district, mules are generally used. The flow of water in the
mines of the district is extremely variable; some have very little;
others have a good deal. The Central mine is one of the wettest in the
entire district, making about 2000 gal. of water per minute. Coal in
southeastern Missouri costs $2 to $2.25 per ton delivered at the mines,
and the cost of raising 2000 gal. of water per minute from a depth
of something like 350 ft. is a very considerable item in the cost of
mining and milling, which, in the aggregate, is expected to come to not
much over $1.25 per ton.
The ore shoots in the district are unusually large. Their precise trend
has not been identified. Some consider the predominance of trend to be
northeast; others, northwest. They go both ways, and appear to make
the greatest depositions of ore at their intersections. However, the
network of shoots, if that be the actual occurrence, is laid out on a
very grand scale. Vertically there is also a difference. Some shafts
penetrate only one stratum of ore; others, two or three. The orebody
may be only a few feet in thickness; it may be 100 ft. or more. The
occurrence of several overlying orebodies obviously indicates the
mineralization of different strata of limestone, while in the very
thick orebodies the whole zone has apparently been mineralized.
The grade of the ore is extremely variable. It may be only 1 or 2 per
cent. mineral, or it may be 15 per cent. or more. However, the average
yield for the district, in large mines which mill 500 to 1200 tons of
ore per day, is probably about 5 per cent. of mineral, assaying 65 per
cent. Pb, which would correspond to a yield of 3.25 per cent. metallic
lead in the form of concentrate. The actual recovery in the dressing
works is probably about 75 per cent., which would indicate a tenure of
about 4.33 per cent. lead in the crude ore.
LEAD MINING IN SOUTHEASTERN MISSOURI
BY R. D. O. JOHNSON
(September 16, 1905)
The lead deposits of southeastern Missouri carry galena disseminated
in certain strata of magnesian limestone. Their greater dimensions
are generally horizontal, but with outlines extremely irregular. The
large orebodies consist usually of a series of smaller bodies disposed
parallel to one another. These smaller members may coalesce, but are
generally separated from one another by a varying thickness of lean ore
or barren rock. The vertical and lateral dimensions of an orebody may
be determined with a fair degree of accuracy by diamond drilling, and a
map may be constructed from the information so obtained. Such a map (on
which are plotted the surface contours) makes it possible to determine
closely the proper location of the shaft, or shafts, considering also
the surface and underground drainage and tramming.
The first shafts in the district were sunk at Bonne Terre, where the
deposits lie comparatively near the surface. The early practice at this
point was to sink a number of small one-compartment shafts. As the
deposits were followed deeper, this gave way to the practice of putting
down two-compartment shafts equipped much more completely than were the
shallower shafts.
At Flat River (where the deposits lie at much greater depths, some
being over 500 ft.) the shafts are 7 × 14 ft., 6½ × 18 ft., and 7 × 20
ft. These larger dimensions give room not only for two cage-ways and a
ladder-way, but also for a roomy pipe-compartment. The large quantities
of water to be pumped in this part of the district make the care of
the pipes in the shafts a matter of first importance. At Bonne Terre
only such a quantity of water was encountered as could be handled by
bailing or be taken out with the rock; there the only pipe necessary
was a small air-pipe down one corner of the shaft. When the quantity
of water encountered is so great that the continued working of the mine
depends upon its uninterrupted removal, the care of the pipes becomes a
matter of great importance. A shaft which yields from 4000 to 5000 gal.
of water per minute is equipped with two 12 in. column pipes and two 4
in. steam pipes covered and sheathed. Moreover, the pipe compartment
will probably contain an 8 in. air-pipe, besides speaking-tubes, pipes
for carrying electric wires, and pipes for conducting water from upper
levels to the sump. To care for these properly there are required a
separate compartment and plenty of room.
Shafts are sunk by using temporary head frames and iron buckets of from
8 to 14 cu. ft. capacity. Where the influx of water was small, 104 ft.
have been sunk in 30 days, with three 8 hour shifts, two drills, and
two men to each drill; 2¾ in. drills are used almost exclusively; 3¼
in. drills have been used in sinking, but without apparent increase in
speed.
The influence of the quantity of water encountered upon the speed of
sinking (and the consequent cost per foot) is so great that figures are
of little value. Conditions are not at all uniform.
At some point (usually before 200 ft. is reached) a horizontal opening
will be encountered. This opening invariably yields water, the amount
following closely the surface precipitation. It is the practice to
establish at this point a pumping station. The shaft is “ringed” and
the water is directed into a sump on the side, from which it is pumped
out. This sump receives also the discharge of the sinking pumps.
The shafts sunk in solid limestone require no timbering other than that
necessary to support the guides, pipes, and ladder platforms. These
timbers are 8 × 8 in. and 6 x 8 in., spaced 7 or 8 ft. apart.
Shafts are sunk to a depth of 10 ft. below the point determined upon
as the lower cage landing. From the end at the bottom a narrow drift
is driven horizontally to a distance of 15 ft.; at that point it is
widened out to 10 ft. and driven 20 ft. further. The whole area (10 ×
20 ft.) is then raised to a point 28 or 30 ft. above the bottom of the
drift from the shaft. The lower part of this chamber constitutes the
sump. Starting from this chamber (on one side and at a point 10 ft.
above the cage landing, or 20 ft. above the bottom of the sump), the
“pump-house” is cut out. This pump-house is cut 40 ft. long and is as
wide as the sump is long, namely, 20 ft. A narrow drift is driven to
connect the top of the pump-house with the shaft. Through this drift
the various pipes enter the pump-house from the shaft.
The pumps are thus placed at an elevation of 10 ft. above the bottom
of the mine. Flooding of mines, due to failure of pumps or to striking
underground bodies of water, taught the necessity of placing the pumps
at such an elevation that they would be the last to be covered, thus
giving time for getting or keeping them in operation. The pumps are
placed on the solid rock, the air pumps and condensers at a lower level
on timbers over the sump.
With this arrangement, the bottom of the shaft serves as an antechamber
for the sump, in which is collected the washing from the mine and the
dripping from the shaft. The sump proper rarely needs cleaning.
The pumps are generally of high-grade, compound-and triple-expansion,
pot-valved, outside-packed plunger pattern. Plants with electrical
power distribution have recently installed direct-connected compound
centrifugal pumps with entire success.
Pumps of the Cornish pattern have never been used much in this region.
One such pump has been installed, but the example has not been followed
even by the company putting it in.
The irregular disposition of the ore renders any systematic plan of
drifting or mining (as in coal or vein mining) impossible. On each
side of the shaft and in a direction at right angles to its greater
horizontal dimension, drifts 12 to 14 ft. in width are driven to a
distance of 60 or 70 ft. In these broad drifts are located the tracks
and also the “crossovers” for running the cars on and off the cage.
When a deposit is first opened up, it is usually worked on two, and
sometimes three, levels. These eventually cut into one another, when
the ore is hoisted from the lower level alone.
The determination of the depth of the lower level is a matter of
compromise. Much good ore may be known to exist below; when it comes
to mining, it will have to be taken out at greater expense; but the
level is aimed to cut through the lower portions of the main body. It
is generally safe to predict that the ore lying below the upper levels
will eventually be mined from a lower level without the expense of
local underground hoisting and pumping.
The ore has simply to be followed; no one can say in advance how it
is going to turn out. The irregularity of the deposits renders any
general plan of mining of little or no value. Some managers endeavor to
outline the deposits by working on the outskirts, leaving the interior
as “ore reserves.” Such reserves have been found to be no reserves at
all, though the quality of the rock may be fairly well determined by
underground diamond drilling. Many of the deposits are too narrow to
permit the employment of any system of outlining and at the same time
keeping up the ore supply.
The individual bodies constituting the general orebody are rarely,
if ever, completely separated by barren rock; some “stringers” or
“leaders” of ore connect them. The careful superintendent keeps a
record on the monthly mine map of all such occurrences, or otherwise,
or of blank walls of barren rock that mark the edge of the deposit.
This precaution finds abundant reward when the drills commence to “cut
poor,” and when a search for ore is necessary.
The method of mining is to rise to the top of the ore and to carry
forward a 6 ft. breast. If the ore is thick enough, this is followed by
the underhand stope. Drill holes in the breast are usually 7 or 8 ft.
in depth; stope holes, 10 to 14 feet.
Both the roof and the floor are drilled with 8 or 10 ft. holes placed
8 or 10 ft. apart. These serve to prospect the rock in the immediate
neighborhood; in the roof they serve the further very important purpose
of draining out water that might otherwise accumulate between the
strata and that might force them to fall. The condition or safety
of the roof is determined by striking with a hammer. If the sound
is hollow or “drummy,” the roof is unsafe. If water is allowed to
accumulate between the loose strata, obviously it is not possible to
determine the condition of the roof.
It is the duty of two men on each shift to keep the mine in a safe
condition by taking down all loose and dangerous masses of rock. These
men are known as “miners.” It sometimes happens that a considerable
area of the roof gets into such a dangerous condition that it is either
too risky or too expensive to put in order, in which case the space
underneath is fenced off. As a general thing, the mines are safe and
are kept so. There are but few accidents of a serious nature due to
falling rock.
The roof is supported entirely by pillars; no timbering whatever is
used. The pillars are parts of the orebody or rock that is left. They
are of all varieties of size and shape. They are usually circular in
cross-section, 10 to 15 ft. in diameter and spaced 20 to 35 ft. apart,
depending upon the character of the roof. Pillars generally flare at
the top to give as much support to the roof as possible. The hight of
the pillars corresponds, of course, to the thickness of the orebody.
All drilling is done by 2¾ in. percussion drills. In the early days,
when diamonds were worth $6 per carat, underground diamond drills were
used. Diamond drills are used now occasionally for putting in long
horizontal holes for shooting down “drummy” roof. Air pressure varies
from 60 to 80 lb. Pressures of 100 lb. and more have been used, but the
repairs on the drills became so great that the advantages of the higher
pressure were neutralized.
Each drill is operated by two men, designated as “drillers,” or “front
hand” and “back hand.” The average amount of drilling per shift of 10
hours is in the neighborhood of 40 ft., though at one mine an average
of 55 ft. was maintained.
In some of the mines the “drillers” and “back hands” do the loading and
firing; in others that is done by “firers,” who do the blasting between
shifts. When the drillers do the firing, there is employed a “powder
monkey,” who makes up the “niphters,” or sticks of powder, in which are
inserted and fastened the caps and fuse; 35 per cent. powder is used
for general mining.
Battery firing is employed only in shaft sinking. In the mining work
this is found to be much more expensive; the heavy concussions loosen
the stratum of the roof and make it dangerous.
Large quantities of oil are used for lubrication and illumination.
“Zero” black oil and oils of that grade are used on the drills. Miners’
oil is generally used for illumination, though some of the mines use a
low grade of felsite wax.
Two oil cans (each holding about 1½ pints) are given to each pair of
drillers, one can for black oil and one for miners’ oil. These cans,
properly filled, are given out to the men, as they go on shift, at the
“oil-house,” located near the shaft underground. This “oil-house” is in
charge of the “oil boy,” whose duty it is to keep the cans clean, to
fill them and to give them out at the beginning of the shift. The cans
are returned to the oil-house at the end of the shift.
Kerosene is used in the hat-lamps in wet places.
The “oil-houses” are provided with three tanks. In some instances these
tanks are charged through pipes coming down the shaft from the surface
oil-house. These tanks are provided with oil-pumps and graduated
gage-glasses.
Shovelers or loaders operate in gangs of 8 to 12, and are supervised by
a “straw boss,” who is provided with a gallon can for illuminating oil.
The cars are 20 cu. ft. (1 ton) capacity. Under ordinary conditions one
shoveler will load 20 of these cars in a shift of 10 hours. They use
“half-spring,” long-handled, round-pointed shovels.
Cars are of the solid-box pattern, and are dumped in cradles. Loose
and “Anaconda” manganese-steel wheels are the most common. Gage of
track, 24 to 30 in., 16 lb. rails on main lines and 12 lb. on the side
and temporary tracks. Cars are drawn by mules. One mine has installed
compressed-air locomotives and is operating them with success.
Shafts are generally equipped with geared hoists, both steam and
electrically driven. Later hoists are all of the first-motion pattern.
Generally the cars are hoisted to the top and dumped with cradles. One
shaft, however, is provided with a 5-ton skip, charged at the bottom
from a bin, into which the underground cars are dumped. Upon arriving
at the top the skip dumps automatically. This design exhibits a number
of advantages over the older method and will probably find favor with
other mine operators.
THE LEAD ORES OF SOUTHWESTERN MISSOURI
BY C. V. PETRAEUS AND W. GEO. WARING
(October 21, 1905)
The lead ore of southwestern Missouri, and the adjoining area in the
vicinity of Galena, Kan., is obtained as a by-product of zinc mining,
the galena being separated from the blende in the jigging process.
Formerly the galena (together with “dry-bone,” including cerussite and
anglesite) was the principal ore mined from surface deposits in clay,
the blende being the subsidiary product. In the deeper workings blende
was found largely to predominate; this is shown by the shipments of the
district in 1904, which amounted to 267,297 tons of zinc concentrate
and 34,533 tons of lead concentrate.
The lead occurs in segregated cubes, from less than one millimeter up
to one foot in diameter. The cleavage is perfect, so that each piece
of ore when struck with a hammer breaks up into smaller perfect cubes.
In this respect the ore differs from the galena encountered in the
Rocky Mountain regions, where torsional or shearing strains seem in
most instances to have destroyed the perfect cleavage of the minerals
subsequent to their original deposition. Cases of schistose and twisted
structure occur in lead deposits of the Joplin district but rarely, and
they are always quite local.
The separation of the galena from the blende and marcasite (“mundic”)
in the ordinary process of jigging is very complete; the percentage
of zinc and iron in the lead concentrate is insignificant. As an
illustration of this, the assays of 100 recent consecutive shipments of
lead ore from the district, taken at random, are cited as follows:
7 shipments assayed from 57 to 70% lead
15 shipments assayed from 70 to 75% lead
46 shipments assayed from 75 to 79% lead
32 shipments assayed from 80 to 84.4% lead
Average of 100 shipments 78.4% lead
Fourteen shipment samples, ranging from 70 to 84.4 per cent. lead, were
tested for zinc and iron. These averaged 2.24 per cent. Fe and 1.78
per cent. Zn, the highest zinc content being 4.5 per cent. No bismuth
or arsenic, and only very minute traces of antimony, have ever been
found in these ores. They contain only about 0.0005 per cent. of silver
(one-seventh of an ounce per ton) and scarcely more than that of copper
(occurring as chalcopyrite).
The pig lead produced from these ores is therefore very pure, soft and
uniform in quality, so that the term “soft Missouri lead” has become a
synonym for excellence in the manufacture of lead alloys and products,
such as litharge, red and white lead, and orange mineral. Its freedom
from bismuth, which is generally present in Colorado lead, makes it
particularly suitable for white lead; also for glass-maker’s litharge
and red lead. These oxides, for use in making crystal glass, must be
made by double refining so as to remove even the small quantities
of silver and copper that are present. The resulting product, made
from soft Missouri lead, is far superior to any refined lead produced
anywhere in this country or in Europe, even excelling the famous
Tarnowitz lead. It gives a luster and clarity to the glass that no
other lead will produce. Lead from southeastern Missouri, Kentucky,
Illinois, Iowa, and Wisconsin yields identical results, but the
refining is more difficult, not only because the lead contains a little
more silver and copper, but also because it contains more antimony.
The valuation of the lead concentrate produced in the Joplin district
is based upon a wet assay, usually the molybdate or ferrocyanide
method. The price paid is determined variously. One buyer pays a
fixed price for average ore, making no deductions; as, for example,
at present rates, $32.25 per 1000 lb. whether the ore assays 75 or 84
per cent. Pb, pig lead being worth $4.75 at St. Louis.[6] Another pays
$32.25 for 80 per cent. ore, or over, deducting 50c. per unit for ores
assaying under 80 per cent. Another pays for 90 per cent. of the lead
content of the ore as shown by the assay, at the St. Louis price of pig
lead, less a smelting charge of, say, $6 to $8 per ton of ore.
The history of the development of lead ore buying in the Joplin
district is rather curious. In the early days of the district the ore
was smelted wholly on Scotch hearths, which, with the purest ores,
would yield 70 per cent. metallic lead. No account was taken of the
lead in the rich slag, chemical determinations being something unknown
in the district at that time; it being supposed generally that pure
galena contained 700 lb. lead to the 1000 lb. of ore, the value of
700 lb. lead, less $4.50 per 1000 lb. of ore for freight and smelting
costs, was returned to the miner. The buyers graded the ore, according
to their judgment, by its appearance, as to its purity and also as to
its behavior in smelting; an ore, for example, from near the surface,
imbedded in the clay and coated more or less with sulphate, yielded its
metal more freely than the purer galenas from deeper workings.
This was the origin of the present method of buying—a system that would
hardly be tolerated except for the fact that the lead is, as previously
stated, considered a by-product of zinc mining.
Originally all the lead ore from the Missouri-Kansas district was
smelted in the same region, either in the air furnace (reverberatory
sweating-furnace) or in the water-back Scotch hearth. Competition
gradually developed in the market. Lead refiners found the pure
sulphide of special value in the production of oxidized products.
Some of the ore found its way to St. Louis, and even as far away as
Colorado, where it was used to collect silver. Since the formation of
the American Smelting and Refining Company and the greatly increased
output of the immense deposits of lead ore in Idaho, no Missouri lead
ore has gone to Colorado.
Up to 1901, one concern had more or less the control of the
southwestern Missouri ores. At the present time, lead ore is bought
for smelters in Joplin, Carterville, and Granby, Mo., Galena, Kan.,
and Collinsville, Ill., and complaint is heard that present prices are
really too high for the comfort of the smelters. Yet the old principle
of paying for lead ores upon the supposed yield of 70 per cent.,
irrespective of the real lead content, is still largely in vogue.
Any one interested in the matter will find it quite instructive to
calculate the returning charges, or gross profits, in smelting these
ores, on the basis of 70 per cent. recovery, at $32.25 per 1000 lb. of
ore, less 50c. per ton haulage, with lead at $4.77 per 100 lb. at St.
Louis. No deduction, it should be remarked, is ever made for moisture
in lead ores in this district. It is of interest to observe that
Dr. Isaac A. Hourwich estimates (in the U. S. Census Special Report
on Mines and Quarries recently issued) the average lead contents of
the soft lead ores of Missouri in 1902 at 68.2 per cent., taking as a
basis the returns from five leading mining and smelting companies of
Missouri, which reported a product of 70,491 tons of lead from 103,428
tons of their own and purchased ore. The average prices for lead ore
in 1902 were reported as follows, per 1000 lb.: Illinois, $19.53;
Iowa, $24.48; Kansas, $23.51; Missouri, $22.17; Wisconsin, $23.29;
Rocky Mountain and Atlantic Coast States, $10.90. In 1903, according
to Ingalls (“The Mineral Industry,” Vol. XII), the ore from the Joplin
district commanded an average price of $53 per 2000 lb., while the
average in the southeastern district was $46.81.