Imágenes de páginas

tions was the discovery that losses ranged from 5 or 6 per cent at some plants to as high as 20 per cent at others. The allowance for losses (wastage) is adjusted periodically.

The duty on lead ore was again cut in half by the act of 1913. The general provisions were not changed except for the provision in the bonded smelting paragraph for the withdrawal of antimonial lead as type metal and cancellation of the bond on lead ore (or bullion) in the amount of the duties so paid.



The factors that enter into the successful exploitation of a given body of lead ore are not essentially different from those that determine the advisability of embarking on any mining venture- labor conditions, extent of the ore body, accessibility, ease of transportation, character of the ore, including the presence of or absence of other valuable or harmful substances. Two factors, however, are of special importance:

1. Location of the mine.-In the early days of the lead industry small smelting units were frequently found at the mines; but the advantages gained by concentration of reduction units at centers of transportation were early recognized. Smelting centers, therefore, are now located more or less distant from the mines, which are scattered over a large tributary territory. The centralization of the smelting operations has resulted in greater economy of fuel, power, and labor in the treatment of the ore but generally involves a longer ore haul from the mine to market (the smeltery). Transportation is, therefore, an almost universal, and frequently, a very important item in the cost of ore.

The location of the mine has also an important bearing on the cost of obtaining supplies and on the character and adequacy of the labor supply. The increased cost of operation due to relative inaccessibility of the mine is often an added deterrent to its successful exploitation.

2. Character of the ore.--All lead ores contain substances other than lead minerals. Some of these substances (e. g., gold, silver, or copper) can be recovered in the smelting process and may add much to the value of the ore. Even substances deleterious in the smelting process (e. g. zinc) may not seriously handicap the operation of the mine, if easily separable, and may even prove valuable assets. On the other hand the presence of deleterious impurities that can not be separated from the valuable constituents of the ore without complicated, expensive, and extra equipment and treatment may prevent the successful exploitation of deposits that would otherwise be sufficiently valuable.

The common impurities in lead ores are silica, iron, lime, barytes, zinc, antimony, and arsenic. The first three (in minor amounts) may be beneficial or detrimental in any given ore, depending upon whether the bulk of the ore supply of the smeltery carries an excess of one or the other of these elements which, in proper proportions, are required in the smelting operation. On the other hand, zinc and, to a much less extent, antimony, are alwars detrimental and detract from the value of the ore unless separated from the lead


before shipment to the smelter. Sulphur, a constituent element of galena, is not considered a deleterious element except that carbonate ores of similar grade are more valuable since they are cheaper to smelt. Barytes and other less common constituents of lead ores, including traces of valuable metals (bismuth, cadmium, and rare elements). are seldom present in quantities suflicient to affect the value of the ore to the miner.

[ocr errors]


On account of the widely differing character of deposits, the broad geographical distribution of districts, and the accompanying variety of ores and conditions, an estimate of the average cost of producing lead ore is a most difficult problem.

This problem is further complicated by the difficulty of ascertaining the correct valuation of the deposit from which the ore is obtained. With the exception of some of the large properties in Missouri which are blocked out by drilling, there are few lead mines anywhere in the world whose available ore reserves can be predicted with reasonable accuracy. The exact determination of the amount of ore that can be ultimately extracted is practically impossible; but this figure must be known in order to allow for depletion. The larger operators make a rough appraisal of the value of their properties and carry this value on their books, writing off a pro rata depletion charge for each ton of ore extracted. This loading charge (depletion) is as truly a part of the cost of production as is the actual operating cost, but its determination is, at best, only approximate. The exhaustion of deposits is often far more rapid than was estimated at first. However, in certain cases two tons of ore will be developed for every ton extracted. This speculative feature is not so marked in lead mining as it is in the case of some other minerals, notably tungsten and gold, but the close estimate of probable returns as applied to iron, coal, and “porphyry” copper operations is rarely possible in the case of lead mining

Another difficulty in determining costs of production is the presence of valuable accessory minerals. With the exception of southeast Missouri there are few districts in which the lead contents of ore must bear the whole burden of the cost of production. The value of precious metals, especially silver, is the very important factor at a great many mines. Frequently the value of the lead will not pay the cost of mining.

In 1911 Mr. E. Gvbbon Spilsbury, in his report 12 to the Tariff Board, estimated that the average cost of producing lead in the "most favored of the western mines” was “not under 3.84 cents per pound of lead in the ore, whereas the actual expenses of preparing the ore for market will not average more than 2.75 cents per pound of lead contents." This statement accords with the prevailing impression as to average costs in the United States prior to the outbreak of the European war. Estimates made during the latter part of the war period assume that the increase in the cost of mining is from 30 to 50 per cent.13

12 In files of the Tariff Commission. 13 Analysis of Bunker Hill and Sullivan 1918 costs, published May 31, 1919, in Mining and Scientific Press, shows 3.64 cents per pound of lead in concentrate as the cost (to the mine) of mining and smelting lead (with full credit for silver recoveries).


There is no question that lead ore is produced more cheaply in many foreign countries--especially Mexico, Spain, and Australia than in the United States. The advantages lie in better ore bodies, lower labor costs, and generally lower freights from mine to market. Canada is probably an exception to this rule and the cost of production and general conditions differ little from those existing in the United States. But in Canada lead mining as well as smelting has been fostered for many years by a bounty which practically guarantees a definite minimum price to the producer.'

The important factor in the domestic market, however, is Mexico. Of all the countries of the world, Mexico is the only country that has any strong probability of materially increasing its production. Spain, Australia, Germany, and the Far East have no excess production that is likely to invade American markets. Even Canada is scarcely self-sufficient as regards lead and the shipment of its ore into the United States, although frequently comparatively large, can not be said to compete actively with the output of domestic mines, since the balance of trade in lead between the two countries is "in favor of the United States. Ore shipments from South America and from Africa are too small to warrant especial attention.

Mexico has large deposits of high-grade lead ore with generally high silver values. The long series of political troubles that followed the orerthrow of the Diaz régime hare served to inhibit the development of resources, and even with a degree of order attained in certain of the more important mining districts in northern Mexico under the Carranza government, the high taxes and continued uncertainty seriously restricted operations.

l'nder normal conditions, such as may be expected later, the Mexican mines will again compete actively with American lead mines. The early effects will be the tendency to expansion of smelting operations along the border and the decline of adjacent mining operations. The effect on the interior districts where, as in Missouri, domestic miners have a high degree of protection because of their relative nearness to the smelteries, would be less immediate, but the general lowering of prices that would conceivably result from the large influx of cheap Mexican ore would render unprofitable the exploitation of many American deposits that, under purely domestic competition, could be successfully worked for many years.


The tariff problem on lead ore is complex. It is closely related to the case of zinc ore, as both lead and zinc are commonly mined together. Both of these metals and their ores have been protected for many years by high duties that have resulted in practical national sufficiency with comparatively small imports or exports except transaction under the bonded smelting provision. This provision permits domestic smelters to import all the special qualities of ore that they may need for the efficient conduct of their operations without the added cost of duty and so far they have had no difficulty in making a profit on the sale of the resultant metal abroad.

" See auxiliary file for survey on lead (metal) (or description of Canadian lead bounty.

Consideration is required of the effect of duties on lead in ore, as
on lead metal, in increasing cost to the consumer.

In former years
the American market differed from the London market by nearly the
full amount of the duty. In later years, however, the differential
between the two markets narrowed and for a short time, just before
the outbreak of the war, the London price was actually higher than
the New York price. Temporarily, at least, the duty did not increase
the cost of metal to the domestic consumer, and after the war the
London and New York markets were for nearly two years practically
independent with the foreign price generally higher than domestie
quotations. Since the latter part of 1920 European prices have
again had a material effect on the American market.

Lead ore-Production in United StatesStates.
(From Mineral Resources, United States Geological Survey.)

[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small]
[blocks in formation]

12, 300, 100

5, 900, 118

5, 367,211

2, 217, 660

581, 100

10, 202, 566

115, 685
1, 406, 000
2,093, 792

58, 349, 188



1, 757
43, 919

158, 936


2, 427


176, 116

5, 468
8, 172
6, 228
83, 063


11, 492, 300
5, 128, 956
4,522, 022
2, 232, 853

763, 920

8, 544, 014

15, 444


10, 869

2, 290

31, 405

173, 000


1, 212


210, 440

2, 271
7, 306

99, 984




1, 866


500, 188

95, 917
1,387, 490
2, 205, 863

52, 578, 896


1, 494


522, 864

22, 759

3, 600, 532

68,783, 340


2, 322


561, 641

Fluorspar from which lead was recovered as a by-product, not included.

Lead ore, mine production, lead contents of all kinds of lead-bearing ore, in short tons-

Production in United States -States.

(From United States Geological Survey, preliminary estimates, February, 1919 (subject to correction).]

[blocks in formation]












105, 897 105, 397 113, 710



139,000 160, 000 175,000

15, 476 18,097


19, 993 22, 312

40, 715 44, 308


54, 940 52, 590 45, 560 16,770 15, 560 22, 745

14, 967

10, 791


16, 226

17,089 16, 487 21,009 18, 823 14,776

20, 226


23, 635 31, 080 28,000


159, 851 161, 287 192, 618


181, 100

16, 710 14, 234 14, 499 18,309 20,684


11, 595


9,424 36, 558

1,583 1, 605


1, 790! 1,368

14, 495 16,684 21, 450


21,67420, 464 21,812 24,362 16, 237

3,907 4,160 3,613




4, 563

4,764 11, 343 15, 807

120, 662 124, 605


109, 717

55, 530

22,000 52, 937 88, 670


11, 266

190, 523

17, 137
189, 810

21, 107


232, 612 203, 000

355 1, 134

190,000 173, 343 180,000 170,000

United Kingdom

1,073 1, 235 1, 396 1,918 2,076

21, 866

3, 174
18, 279 19, 473

'nited Kingdom

18, 462 19,684 | 15, 767 12, 775


11, 431

8, 255

Cnited States, for

30, 500


353, 186

368, 301 376, 947 396, 034 485, 011 487,177 540, 892 527, 729 499,618

Total .......... 1,093, 043 1, 108, 880 1, 212, 252 1, 142, 264


1 From Mineral Industry. From official reports as far as possible.

: From domestic ore.

: From foreign ore not elsewhere shown.

* The totals may be high on account of duplications that can not be eliminated.

« AnteriorContinuar »