The Economic Aspect of Geology Part 16

Asphalt and bitumen find their main use in paving. Other important uses are in paints and varnishes, in the manufacture of prepared roofing, for various insulating purposes, and in subst.i.tutes for rubber.

Nearly the entire world's supply of natural asphalt comes from the British Island of Trinidad and from Venezuela. Both of these deposits are under United States commercial control probably affiliated with Dutch-English interests. Prior to the war about half the product went to Europe and half to the United States. Large amounts of asphaltic and bituminous rock, used mainly in paving, are normally produced in Alsace, France, and in Italy. Prior to the war both the Alsatian and Italian deposits were under German commercial control. Their output is practically all consumed in Europe.

The United States takes a large part in the world's trade in natural asphalt, by importation from Trinidad and Venezuela, and by some reexportation chiefly to Canada and Mexico. The United States also produces some natural asphalt and bituminous rock for domestic consumption. Deposits of natural asphaltic material are widely distributed through the United States, but commercial production is limited to a few localities in Kentucky, Texas, Utah, Colorado, Oklahoma, and California.

The asphalt manufactured from petroleum const.i.tutes a much larger tonnage than natural asphalt though it does not enter so largely into world trade. The manufactured product is largely but not exclusively in American control. Large amounts are made in this country and will no doubt be made for the next decade, from oil produced in the southwestern states and in Mexico. At the present time as much or more asphalt is made in the United States from Mexican as from domestic crude oil. The refineries are located near the Gulf coast so that exports can avoid overland shipments. The relative merits of natural asphalt and asphalt manufactured from oil may be subject to some discussion; but it is perfectly clear that the manufactured material is sufficient, both in quant.i.ty and variety, to make the United States entirely independent and have an exportable surplus.

GEOLOGIC FEATURES

Natural asphalt and similar products are in the main merely the residuals of oil and gas distillation acc.u.mulated by nature under certain conditions already described in connection with oil (pp.

140-144). In some cases the asphaltic material is found as impregnations of sediments, and appears to have remained in place while the lighter organic materials were volatilized and migrated upward. In other cases it occurs in distinct fissure veins; the fissures and cavities apparently were once filled with liquid petroleum, which has subsequently undergone further distillation. The original liquid character of some of these bitumens is shown by occasional fragments of unworn "country rock" imbedded in the veins. The effect of surface waters, carrying oxidizing materials and sulphuric acid, is believed to have contributed to the drying out and hardening of these veins or dikes.

Asphalts and bitumens include a wide variety of hydrocarbon materials, such as gilsonite, grahamite, elaterite, ozokerite, etc., which are used for somewhat different purposes. The deposits of the United States show much variety in form, composition, age, and geologic a.s.sociations. The important Kentucky deposits occur as impregnations of Carboniferous sandstones at the base of the Coal Measures of that state.

The Trinidad asphalt comes from the famous "pitch lake," which is a nearly circular deposit covering about a hundred acres 150 feet above sea level, and which is believed to fill the crater of an old mud volcano. The so-called pitch consists of a mixture of bitumen, water, mineral and vegetable matter, the whole inflated with gas, which escapes to some extent and keeps the ma.s.s in a state of constant ebullition. The surface of the lake is hard, and yet the ma.s.s as a whole is plastic and tends to refill the excavations. The lake is believed to be on the outcrop of a petroleum-bearing stratum, and the pitch to represent the unevaporated residue of millions of tons of petroleum which have exuded from the oil-sands. The pitch is refined by melting,--the heat expelling the water, the wood and other light impurities rising, and the heavy mineral matter sinking to the bottom.

The asphalt of Venezuela is similar in nature, but the pitch "lake" is here covered with vegetation and the soft pitch wells up at certain points as if from subterranean springs.

FOOTNOTES:

[17] For more detailed treatment of international coal movements before the war and of coal movements within the United States, see the U. S.

Geological Survey's _World Atlas of Commercial Geology_, Pt. 1, 1921, pp. 11-16.

[18] Campbell, Marius R., The coal fields of the United States: _Prof.

Paper 100-A, U. S. Geol. Survey_, 1917, pp. 5, 6, 7.

[19] Compiled from tables quoted by White, David, The petroleum resources of the world: _Annals Am. Acad. Social and Political Sci._, vol. 89, 1920, pp. 123 and 126.

[20] White, David, _loc. cit._, p. 113.

[21] See Arnold, Ralph, Petroleum resources of the United States: _Econ.

Geol._, vol. 10, 1915, p. 707.

[22] White, David, Late theories regarding the origin of oil: _Bull.

Geol. Soc. Am._, vol. 28, 1917, p. 732.

[23] McCoy, A. W., Notes on principles of oil acc.u.mulation: _Jour.

Geol._, vol. 27, 1919, pp. 252-262.

[24] White, David, Genetic problems affecting search for new oil regions: _Mining and Metallurgy_, _Am. Inst. of Min. Engrs._, No. 158, Sec. 21, Feb., 1920.

[25] Mehl, M. G., Some factors in the geographic distribution of petroleum: _Bull. Sci. Lab._, _Denison Univ._, vol. 19, 1919, pp. 55-63.

[26] Schuchert, Charles, Petroliferous provinces: _Bull. 155_, _Am.

Inst. Mining and Metallurgical Engrs._, 1919, pp. 3059-3060.

[27] Loc. cit., p. 20.

[28] Seepages or residual bituminous matter near the surface may be due to upward escape of oil material through joints in the rocks capping a reservoir, and productive pools may be found directly below such showings. In other regions similar surface indications may mean that the stratum in the outcrop of which they are found is oil-bearing; but acc.u.mulations of oil, if present, may be several miles down the dip, at places where the structural conditions have been favorable. In still other cases the seepage may have been in existence for such a long time as to exhaust the reservoir. It must also be remembered that gas seeps are common in sloughs and marshes where vegetation is decaying, and may be of no significance in the search for petroleum.

[29] Arnold, Ralph, Conservation of the oil and gas resources of the Americas: _Econ. Geol._, vol. 11, 1916, pp. 321-322.

[30] Oil shales may also be made to yield large quant.i.ties of fuel and illuminating gas, and of ammonia (see pp. 101-102).

CHAPTER IX

MINERALS USED IN THE PRODUCTION OF IRON AND STEEL (THE FERRO-ALLOY GROUP)

GENERAL FEATURES

Iron and steel and their alloys are the most generally used of the metals. The raw materials necessary for their manufacture include a wide variety of minerals.

Iron is the princ.i.p.al element in this group; but in the manufacture of iron and steel, manganese, chromium, nickel, tungsten, molybdenum, vanadium, zirconium, t.i.tanium, aluminum, uranium, magnesium, fluorine, silicon, and other substances play important parts, either as accessories in the furnace reactions or as ingredients introduced to give certain qualities to the products.

Nearly all parts of the world are plentifully supplied with iron ores for an indefinite period in the future, but their abundant use has thus far been confined mainly to the countries bordering the North Atlantic,--the United States, Germany, and England,--which, possessing ample coal supplies, have had the initiative to develop great iron and steel industries. China has abundant coal, moderate quant.i.ties of iron ore, and a large population, but a low per capita consumption of iron and steel products. Development of its iron and steel industry is just beginning. j.a.pan has neither coal nor iron in sufficient quant.i.ties, and hence the j.a.panese effort in recent years to control the mineral resources of China and other countries. As a result of the war Germany has been largely deprived of its iron ores, and France may a.s.sume somewhat the rank in iron ore production once held by Germany. Sweden and Spain have been considerable producers of iron ore, but both lack coal, with the result that their ores have been largely exported to England and Germany. With increase of per capita consumption in outlying parts of the world, iron and steel industries are beginning to develop locally on a small scale, as in India, South Africa, and Australia.

Russia has had sufficient supplies of coal and iron, but the stage of industrial development in that country has not called for great expansion of its iron and steel industry.

There has been a tendency for iron and steel manufacture to become concentrated at a comparatively few places on the globe favored by the proper combinations of coal, iron, transportation, proximity to consuming populations, initiative and capacity to take advantage of a situation, and other factors. Even though on paper conditions may seem to be favorable in outlying territories for the development of additional plants, this development is often held back by compet.i.tion from the established centers. On the west coast of the United States, there are raw materials for an iron and steel industry and there has been discussion for years as to the possibilities of starting a successful large scale steel industry. The consuming power of the local population for all kinds of iron and steel would seem to be great enough to warrant such action. However, the demand is for an extremely varied a.s.sortment of iron and steel products; and to start an industry, making only a few of the cruder products such as pig iron and semi-finished forms, would not meet this demand. All varieties of finishing plants and a.s.sociated factories would also need to be started in order to meet the situation. This would require large capital. Furthermore the local demand for some of the accessory finished products might not warrant the establishment of the accessory plants.

Throughout the history of the iron and steel business there has been a marked tendency for the iron ore to move to regions of coal production rather than for the coal to move to the iron ore regions. The coal or energy factor seems ultimately to control. This is due in considerable part to the fact that coal furnishes the basis of a great variety of industries for which iron ore is only one of the feeders, and which are so interrelated that it is not always easy to move the iron and steel industry to a spot near the sources of iron ore where iron and steel alone could be produced.

In regard to iron ore supplies of proper grade and quant.i.ty, the United States is more nearly self-sufficing than any of its compet.i.tors. It imports minor amounts of ore from Cuba and Canada, and even from Chile and Sweden, to border points, in the main merely because these imported ores can compete on a price basis with the domestic ores. The entire exclusion of these ores, however, would make comparatively little difference in the total volume of our iron and steel industry; though it would probably make some difference in distribution, to the disadvantage of plants along the coast. There is only one kind of iron ore in which the United States has anything approaching deficiency, and that is ore extremely low in phosphorus, adapted to making the so-called low-phosphorus pig which is needed for certain special steels. Ordnance requirements during the war put a premium on these steels. While some of these extremely low-phosphorus ores are mined in the United States, additional quant.i.ties have been required from Spain and Canada and to a lesser extent from North Africa and Sweden. Also the Spanish pyrite, imported ordinarily for its sulphur content, on roasting leaves a residue of iron oxide extremely low in phosphorus which is similarly used. The elimination of pyrite imports from Spain during the war, therefore, was a considerable contributing factor to the stringency in low-phosphorus iron ores. War experience showed that the United States was dependent on foreign sources for 40 per cent or upwards of its needs in this regard. Certain developments in progress, notably the project for concentration of siliceous eastern Mesabi Range ores, make it likely that future domestic production will more nearly be able to meet the requirements.

The equivalent of 15 per cent of the iron ore mined in the United States is exported as ore to Canadian ports on the Great Lakes and in the form of crude iron and steel products to many parts of the world. England and Germany are almost the sole compet.i.tors in the export trade.

When we turn to the minerals used for making the alloys of iron and as accessories in the manufacture of iron, it appears that no one of the princ.i.p.al iron and steel producing countries of the world is self-supporting, but that these "sweeteners" must be drawn in from the far corners of the earth. The importance of these minor const.i.tuents is altogether out of proportion to their volume. For instance, only fourteen pounds of manganese are necessary in the making of a ton of steel, yet a ton of steel cannot be made without manganese. The increasing specialization in iron and steel products, and the rapidly widening knowledge of the qualities of the different alloys, are constantly shifting the demand from one to the other of the ferro-alloy minerals. Each one of the ferro-alloy minerals may be regarded as being in the nature of a key mineral for the iron and steel industry, and the control of deposits of these minerals is a matter of international concern. Control is not a difficult matter, in view of the fact that the princ.i.p.al supplies of practically every one of the alloy minerals are concentrated in comparatively few spots on the globe,--as indicated on succeeding pages.

Nature has not endowed the United States, nor in fact the North American continent, with adequate high-grade supplies of the princ.i.p.al ferro-alloy minerals,--with the exception of molybdenum, and with the exception of silica, magnesite, and fluorspar, which are used as accessories in the process of steel making. With plenty of iron ore and coal, and with an iron and steel capacity amounting to over 50 per cent of the world's total, the United States is very largely dependent on other countries for its supplies of the ferro-alloy minerals. The war brought this fact home. With the closing of foreign sources of supplies, it looked at one time as if our steel industry was to be very greatly hampered; and extraordinary efforts were made to keep channels of importation open until something could be done in the way of development, even at excessive cost, of domestic supplies. The result of war efforts was a very large development of domestic supplies of practically all the ferro-alloy minerals; but in no case, with the exceptions noted above, did these prove sufficient to meet the total requirements. This development was at great cost and at some sacrifice to metallurgical efficiency, due to the low and variable grades of the raw materials. With the post-war reopening of importation much of the domestic production has necessarily ceased, and large amounts of money patriotically spent in the effort to meet the domestic requirements have been lost. These circ.u.mstances have resulted in the demand in Congress from producers for direct financial relief and in demand for protective tariffs, in order to enable the new struggling industries to exist, and to permit of development of adequate home supplies. Such tariffs might be beneficial to these particular domestic industries if wisely planned; but also, in view of the limited amounts of these particular ores in this country, their general low grade, and the high cost of mining, tariffs might very probably hasten exhaustion of our limited supplies and might handicap our metallurgical industries both in efficiency and cost (see pp. 365-366, 393-394).

IRON ORES

ECONOMIC FEATURES

=Technical and commercial factors determining use of iron ore minerals.= Popularly, an iron ore is an iron ore, and there is little realization of its really great complexity of composition and the difficulty of determining what is or is not a commercial ore. Percentage of iron is of course an important factor; but an ore in which the iron is in the mineral hemat.i.te is more valuable than one with an equivalent percentage of iron which is in the form of magnet.i.te. Substances present in the ore in minor quant.i.ties, such as phosphorus, sulphur, and t.i.tanium, have a tendency to make the iron product brittle, either when it is cold or when it is being made, so that excessive amounts of these substances may disqualify an ore. Excessive quant.i.ties of silica, lime, or magnesia may make the ore undesirable. Where an acid substance, like silica, is balanced by basic const.i.tuents like lime and magnesia, considerable amounts of both may be used. Excessive moisture content may spoil an ore because of the amount of heat necessary to eliminate it in smelting.

The metallurgical processes of the iron and steel industry are essentially adapted to the princ.i.p.al grades of ore available. The cheapest of the steel-making processes, called the acid Bessemer process, requires a very low-phosphorus ore (usually below .050 per cent in the United States and below .030 per cent in England.) The basic open-hearth processes, making two-thirds of the steel in the United States, allow higher percentages of phosphorus, but not unlimited amounts. The basic Bessemer (Thomas) process, used for the "minette"

ores of western Europe and the Swedish magnet.i.tes, may use an ore with any amount of phosphorus over 1.5 per cent. The phosphatic slag from this process is used as fertilizer. The supply of low-phosphorus Bessemer ore in the United States is at present limited as compared with that of the non-Bessemer ores, with the result that steel-plant construction for many years past has been largely open-hearth. The open-hearth process is favored also because it allows closer control of phosphorus content in the steel.

Small but increasing amounts of steel are also made in the electric furnace; for the most part, however, this process is more expensive than the others, and it is used princ.i.p.ally for special alloy steels.

Iron ores are seldom so uniform in quality that they can be shipped without careful attention to sampling and grade. In the Lake Superior region the ores are sampled daily as mined, and the utmost care is taken to mix and load the ore in such a way that the desired grades can be obtained. Ordinarily a single deposit produces several grades of ore.

When ores are put into the furnace for smelting the mixtures are selected with great care for the particular purpose for which the product is to be used. The mixture is compounded as carefully as a druggist's prescription. An ore salesman, after ascertaining the nature of the iron and steel products of a plant, has to use great skill in offering particular ores for sale which not only will meet the desired grade in regard to all elements, but also will meet compet.i.tion in price. In some respects, the marketing of different grades of iron ore is as complex as the marketing of a miscellaneous stock of merchandise.