Ore deposit

“ The ore deposits are usually discovered by the cherty masses of silicious rock, which, being harder than the limestone, stand out from its weathered surface in bunches and small, vein-like masses. Often in 77 breaking the cherty rocks, stains of copper carbonate are found, and from such rock silver, and sometimes gold, is obtained. Numerous shafts, cuts, and tunnels have been made on these claims, twenty or more in number, and in every one ore of good grade has been found, although the quantity is usually small. ”

“ Every find of "values" in a placer is unquestioned evidence that somewhere, [63] above the present deposit, there originally existed primary depositions containing the valuable metals or minerals. The trail can frequently be traced back to them. These so-called "mother lodes" are not necessarily rich. In the case of gold, for instance, these original deposits of ore may not carry the metal in coarse enough particles to be visible and yet the placers may contain nuggets. ”

“ This method of stoping is only applicable when:—
1. The deposit dips over 60°, and thus broken material will freely settle downward to be drawn off from the bottom.
2. The ore is consistently payable in character. No selection can be done in breaking, as all material broken must be drawn off together.
3. The hanging wall is strong, and will not crush or spall off waste into the ore.
4. The ore-body is regular in size, else loose ore will lodge on the foot wall. Stopes opened in this manner when partially empty are too dangerous for men to enter for shoveling out remnants. ”

“ Other questions also often arise which are of equal importance to haulage costs. Separate ore-shoots or ore-bodies or parallel deposits necessitate, if worked from one shaft, constant levels through unpayable ground and extra haul as well, or ore-bodies may dip away from the original shaft along the strike of the deposit and a long haulage through dead levels must follow. For instance, levels and crosscuts cost roughly one-quarter as much per foot as shafts. ”

“ This ore is frequently almost as hard as iron itself, many of the pieces thus dislodged being too large for convenient handling, either by the steam shovel or in the chutes at the wharves, and must be still further broken up. This is sometimes done by the men with picks; but in mining on a large scale, where the deposit is all of a very hard nature, crushing machines are used. ”

“ 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. ”

“ Where two shafts are to be sunk to inclined deposits, it is usual to set one so as to intersect the deposit at a lower point than the other. Production can be started from the shallower, before the second is entirely ready. The ore above the horizon of intersection of the deeper shaft is thus accessible from the shallower shaft, and the difficulty of long rises or crosscuts from that deepest shaft does not arise. ”

“ If the term of years required to redeem the capital and pay an interest upon it is greater than the life in sight, then this extended life must come from extension in depth, or ore from other direction, or increased price of metals. If we then take the volume and profit on the ore as disclosed we can calculate the number of feet the deposit must extend in depth, or additional tonnage Page 45 that must be obtained of the same grade, or the different prices of metal that must be secured, in order to satisfy the demanded term of years. ”

“ Sometimes enterprises failed because the deposit turned out to be too small, sometimes because the ore did not keep up to the standard, and not infrequently mining companies fell by the wayside because of bad management. Enough evidence of mineral wealth has been found to justify the belief that workable deposits do exist, and to warrant careful further investigation, especially as the means of communication are extended. ”

“ The exploration of the Surigao iron deposit has been completed. In relation to this deposit, the National Development Company has had experiments made in the United States and Europe to determine the best process that should be adopted for the most economical utilization of the ore. Exploration of coal deposits has shown that several sections can be commercially operated. The Cebu Portland Cement Company is now exploiting the Uling coal mine in Cebu to its ad­vantage. ”

“ Below the oxidized outcrop the vein is often increased in value by secondary enrichment, sometimes to a depth of several hundred feet. In the case of such altered deposits surface exploration alone is likely to be misleading, and it is important to push the underground exploration far enough to reach the unaltered part of the deposit, or at least deep enough to make it certain that there is a sufficient quantity of altered or enriched ore to form the basis of profitable mining operations. ”

“ A metalliferous rock is spoken of as an ore when it contains metallic minerals (or in some cases non-metallic minerals, such as sulphur) in such quantities and mixtures as to make possible their profitable extraction. The metal contained in an ore is sometime found in its elemental form, as in the case of gold or platinum, but more frequently as a sulphur compound, or as an oxide carbonate or silicate. Often several different forms of one metallic element are found in the same deposit and several metals are often found together. ”

“ This deposit occurs at many points along the outcrop of the Clinton group all the way around from Wisconsin, through Canada and New York, into Pennsylvania, and down the eastern slope of the Appalachian range to Georgia, and is said to be the most extensive deposit of iron ore in the world yet discovered. The fossil ore, though large in quantity, contains too much phosphorus to be used for making steel in the ordinary method ”

“ The claim is made for this book that it fills a vacancy in our scientific literature, for no complete review of the ore deposits in our country has appeared since the publication of Whitney's Metallic Wealth in the United States in 1854. Yet within the last forty years enormous developments have been made in new mining districts, the relative importance of different regions has changed, and great advances have been made in our theoretical knowledge regarding the origin and formation of ore beds. ”

“ For instance, in ordinary times considerable quantities of high-phosphorus iron ores are mined; but, because of the fact that such ores require more time for conversion into steel, war-time practice concentrated on the higher-grade, low-phosphorus ores, resulting in an unbalanced production which in some cases amounted almost to robbing of ore deposits. In the case of coal, quantity was almost the only consideration; it was impossible to grade and distribute the coal to meet the specialized demands of industry. ”

“ Especially in connexion with ore-deposits widening experience has modified the older conceptions of relative values in the several types. In the early days of geology, Cornwall and Saxony were the two regions where the most active and influential students of ore-deposits were trained and where the principal books relating to mining originated. The pronounced and characteristic fissure veins of England and Germany became the standards to which the phenomena met elsewhere were referred, and by means of which they were described. ”

“ Perhaps no other portion of the earth's surface is so rich in mineral resources as that which has been covered by these observations, and nowhere else is to be found as great a variety of ore deposits, or those which illustrate as well their mode of formation. This is so true that it maybe said without exaggeration that no one can intelligently discuss the questions that have been raised in regard to the origin and mode of formation of ore bodies without transversing and studying the great mining belt of our Western States and Territories. ”

“ Beginning from little, when the existence, character, and extent of the ore deposits are problematical, it may increase steadily or rapidly so long as discovery and development outrun depletion, and the wiping out of the value by the practical exhaustion of the mine may be deferred for a long term of years. ”

“ The lead-ore deposits in the United States have large possibilities, but with the exception of the disseminated lead deposits of southeastern Missouri the developed ore reserves will supply production for only a few years. Control of the mines in the United States is vested almost exclusively in Americans or American companies, some of the latter, however, having foreign stockholders, chiefly British or Canadian. ”

“ A survey of the ore deposits of Utah has suggested the generalization that ores are more commonly related to intrusive stocks than to the forms known as laccoliths, and that within and about intrusive stocks the ores are much more abundant near the top or apex of a stock than lower down. [6] In parts of the region where erosion has removed all but the deeper portions of the stocks, ore bodies are less abundant. It will be of interest to follow the testing of this generalization in other parts of the world.
The scientist is constantly groping for underlying simple truth. ”

“ For instance, coal can in some cases be carried by rail for 400 miles and delivered on board vessels for from $2 to $2.25 per ton, and yet the mine owners and railroads make dividends; some of the manufacturing establishments in Western Pennsylvania obtain coal at from 60 to 75 cents per ton at their works; hard gold-bearing quartz can be crushed, washed and 95 per cent. of the gold saved on the plates for $1.25 per ton; high grade Bessemer iron ore can be mined, handled, shipped and delivered a thousand miles from the point of production for less than $4.00 per ton. ”

“ In mining regions where water transportation is interrupted during certain months of the year the mineral must be stored underground, or in great stock-piles on the surface. In coal mining the market demand varies in different seasons, and surface storage is sometimes necessary to permit regular work at the mines. For coal, iron ore and other cheap minerals, mechanical handling by many different methods is used in loading and unloading railway wagons and vessels, and in forming the stock-piles and reloading the mineral therefrom. ”

“ When our mining experts discover a mineral belt containing precious metals or copper, iron, lead, nickel, platinum, cobalt, quicksilver, manganese or any other ore used in manufactures and the arts, the first thing we do is to sink a shaft on the most likely ore chimney and at every one hundred feet in depth we run levels to develop it and if we continue to find ore as we go down and the ground requires drainage, we survey for a drainage tunnel that will drain the mine at the greatest depth, even if we have to run a tunnel ten miles. ”

“ Seven lodes, which are distinct and well defined, have been followed for a distance of over 6,000 feet{319} through the property, and five separate workings have been undertaken to test the value of the mineral deposits. As the workings are 750 feet above sea level, at which depths the lodes usually improve, the quantity of ore in the property must consequently be very considerable. The ore also yields both silver and gold, but it is not possible to estimate the profit likely to be made from this source. ”

“ Replacement implies the precipitation of the ore and gangue, molecule by molecule, in the position of the original minerals but without, as in pseudomorphs, the necessary reproduction of crystalline forms. Some waterway must of course introduce the ore-bearing solutions, but it may be slight compared with the great size of the resulting ore-bodies. Lead and zinc ores, often carrying some silver, are those most widely distributed, as they were also the earliest recognized in deposits of this character. More than any other metals their association with limestone is pronounced. ”

“ The aggregate freight charge borne on the average by the 100 pounds of paper which sells at the factory for $2.50 is therefore 30 cents.
As with all things else, the rates on the ores of the far western region have been adjusted under the necessity of the transportation agencies to so serve the mines that their products may be marketed. The rate upon the ore from the mine to the smelter, upon the metal from the smelter to the refinery, and upon the refined lead or refined copper from Chicago to the seaboard market, are all determined by this prime factor. ”

“ Where metals occur like plums in a pudding, sampling becomes difficult and unreliable, and where experience has proved a sort of regularity of recurrence of these plums, dependence must necessarily be placed on past records, for if their reliability is to be questioned, resort must be had to extensive test-treatment runs. The Lake Superior copper mines and the Missouri lead and zinc mines are of this type of deposit. ”

“ The cargoes are usually consigned to a particular class of brokers, indigenous to Swansea, and known as 'copper-ore agents.' The ore is by them deposited in large yards, where it is crushed to a certain fineness, for the purpose of obtaining a proper admixture of the 'heap.' Notice is then given to the different smelting-houses, who procure samples of the lot, and assay it. Meetings are held once a fortnight at the Mackworth Arms Hotel; and on these days the agents for the ore and those for the smelter take their seats around a table. ”